[PATCH/RFC v6 0/3] LED / flash API integration - LED Flash Class

[PATCH/RFC v6 0/3] LED / flash API integration - LED Flash Class

[Jacek Anaszewski]

This patch set is the follow-up of the LED / flash API integration
series [1]. For clarity reasons the patchset has been split into
four subsets:

- LED Flash Class
- V4L2 Flash
- LED Flash Class drivers
- Documentation

========================
Changes since version 5:
========================

- removed flash manager framework - its implementation needs
  further thorough discussion.
- removed external strobe facilities from the LED Flash Class
  and provided external_strobe_set op in v4l2-flash. LED subsystem
  should be strobe provider agnostic.

Thanks,
Jacek Anaszewski

[1] https://lkml.org/lkml/2014/7/11/914


Jacek Anaszewski (3):
  leds: implement sysfs interface locking mechanism
  leds: add API for setting torch brightness
  leds: Add LED Flash Class wrapper to LED subsystem

 drivers/leds/Kconfig            |   11 +
 drivers/leds/Makefile           |    1 +
 drivers/leds/led-class-flash.c  |  557 +++++++++++++++++++++++++++++++++++++++
 drivers/leds/led-class.c        |   30 ++-
 drivers/leds/led-core.c         |   32 +++
 drivers/leds/led-triggers.c     |   16 +-
 include/linux/led-class-flash.h |  238 +++++++++++++++++
 include/linux/leds.h            |   56 ++++
 8 files changed, 934 insertions(+), 7 deletions(-)
 create mode 100644 drivers/leds/led-class-flash.c
 create mode 100644 include/linux/led-class-flash.h

-- 
1.7.9.5

[PATCH/RFC v6 1/3] leds: implement sysfs interface locking mechanism

[Jacek Anaszewski]

Add a mechanism for locking LED subsystem sysfs interface.
This patch prepares ground for addition of LED Flash Class
extension, whose API will be integrated with V4L2 Flash API.
Such a fusion enforces introducing a locking scheme, which
will secure consistent access to the LED Flash Class device.

The mechanism being introduced allows for disabling LED
subsystem sysfs interface by calling led_sysfs_disable function
and enabling it by calling led_sysfs_enable. The functions
alter the LED_SYSFS_DISABLE flag state and must be called
under mutex lock. The state of the lock is checked with use
of led_sysfs_is_disabled function. Such a design allows for
providing immediate feedback to the user space on whether
the LED Flash Class device is available or is under V4L2 Flash
sub-device control.

Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Bryan Wu <cooloney@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
---
 drivers/leds/led-class.c    |   19 ++++++++++++++++---
 drivers/leds/led-core.c     |   18 ++++++++++++++++++
 drivers/leds/led-triggers.c |   16 +++++++++++++---
 include/linux/leds.h        |   32 ++++++++++++++++++++++++++++++++
 4 files changed, 79 insertions(+), 6 deletions(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 2e124aa2..a39ca8f 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -39,17 +39,27 @@ static ssize_t brightness_store(struct device *dev,
 {
 	struct led_classdev *led_cdev = dev_get_drvdata(dev);
 	unsigned long state;
-	ssize_t ret = -EINVAL;
+	ssize_t ret;
+
+	mutex_lock(&led_cdev->led_access);
+
+	if (led_sysfs_is_disabled(led_cdev)) {
+		ret = -EBUSY;
+		goto unlock;
+	}
 
 	ret = kstrtoul(buf, 10, &state);
 	if (ret)
-		return ret;
+		goto unlock;
 
 	if (state == LED_OFF)
 		led_trigger_remove(led_cdev);
 	__led_set_brightness(led_cdev, state);
 
-	return size;
+	ret = size;
+unlock:
+	mutex_unlock(&led_cdev->led_access);
+	return ret;
 }
 static DEVICE_ATTR_RW(brightness);
 
@@ -213,6 +223,7 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
 #ifdef CONFIG_LEDS_TRIGGERS
 	init_rwsem(&led_cdev->trigger_lock);
 #endif
+	mutex_init(&led_cdev->led_access);
 	/* add to the list of leds */
 	down_write(&leds_list_lock);
 	list_add_tail(&led_cdev->node, &leds_list);
@@ -266,6 +277,8 @@ void led_classdev_unregister(struct led_classdev *led_cdev)
 	down_write(&leds_list_lock);
 	list_del(&led_cdev->node);
 	up_write(&leds_list_lock);
+
+	mutex_destroy(&led_cdev->led_access);
 }
 EXPORT_SYMBOL_GPL(led_classdev_unregister);
 
diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index 0d15aa9..cca86ab 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -142,3 +142,21 @@ int led_update_brightness(struct led_classdev *led_cdev)
 	return ret;
 }
 EXPORT_SYMBOL(led_update_brightness);
+
+/* Caller must ensure led_cdev->led_access held */
+void led_sysfs_disable(struct led_classdev *led_cdev)
+{
+	lockdep_assert_held(&led_cdev->led_access);
+
+	led_cdev->flags |= LED_SYSFS_DISABLE;
+}
+EXPORT_SYMBOL_GPL(led_sysfs_disable);
+
+/* Caller must ensure led_cdev->led_access held */
+void led_sysfs_enable(struct led_classdev *led_cdev)
+{
+	lockdep_assert_held(&led_cdev->led_access);
+
+	led_cdev->flags &= ~LED_SYSFS_DISABLE;
+}
+EXPORT_SYMBOL_GPL(led_sysfs_enable);
diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
index c3734f1..e8b1120 100644
--- a/drivers/leds/led-triggers.c
+++ b/drivers/leds/led-triggers.c
@@ -37,6 +37,14 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
 	char trigger_name[TRIG_NAME_MAX];
 	struct led_trigger *trig;
 	size_t len;
+	int ret = count;
+
+	mutex_lock(&led_cdev->led_access);
+
+	if (led_sysfs_is_disabled(led_cdev)) {
+		ret = -EBUSY;
+		goto unlock;
+	}
 
 	trigger_name[sizeof(trigger_name) - 1] = '\0';
 	strncpy(trigger_name, buf, sizeof(trigger_name) - 1);
@@ -47,7 +55,7 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
 
 	if (!strcmp(trigger_name, "none")) {
 		led_trigger_remove(led_cdev);
-		return count;
+		goto unlock;
 	}
 
 	down_read(&triggers_list_lock);
@@ -58,12 +66,14 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
 			up_write(&led_cdev->trigger_lock);
 
 			up_read(&triggers_list_lock);
-			return count;
+			goto unlock;
 		}
 	}
 	up_read(&triggers_list_lock);
 
-	return -EINVAL;
+unlock:
+	mutex_unlock(&led_cdev->led_access);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(led_trigger_store);
 
diff --git a/include/linux/leds.h b/include/linux/leds.h
index f8b2f58..44c8a98 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -13,6 +13,7 @@
 #define __LINUX_LEDS_H_INCLUDED
 
 #include <linux/list.h>
+#include <linux/mutex.h>
 #include <linux/rwsem.h>
 #include <linux/spinlock.h>
 #include <linux/timer.h>
@@ -42,6 +43,7 @@ struct led_classdev {
 #define LED_BLINK_ONESHOT	(1 << 17)
 #define LED_BLINK_ONESHOT_STOP	(1 << 18)
 #define LED_BLINK_INVERT	(1 << 19)
+#define LED_SYSFS_DISABLE	(1 << 20)
 
 	/* Set LED brightness level */
 	/* Must not sleep, use a workqueue if needed */
@@ -85,6 +87,9 @@ struct led_classdev {
 	/* true if activated - deactivate routine uses it to do cleanup */
 	bool			activated;
 #endif
+
+	/* Ensures consistent access to the LED Flash Class device */
+	struct mutex		led_access;
 };
 
 extern int led_classdev_register(struct device *parent,
@@ -151,6 +156,33 @@ extern void led_set_brightness(struct led_classdev *led_cdev,
  */
 extern int led_update_brightness(struct led_classdev *led_cdev);
 
+/**
+ * led_sysfs_disable - disable LED sysfs interface
+ * @led_cdev: the LED to set
+ *
+ * Disable the led_cdev's sysfs interface.
+ */
+extern void led_sysfs_disable(struct led_classdev *led_cdev);
+
+/**
+ * led_sysfs_enable - enable LED sysfs interface
+ * @led_cdev: the LED to set
+ *
+ * Enable the led_cdev's sysfs interface.
+ */
+extern void led_sysfs_enable(struct led_classdev *led_cdev);
+
+/**
+ * led_sysfs_is_disabled - check if LED sysfs interface is disabled
+ * @led_cdev: the LED to query
+ *
+ * Returns: true if the led_cdev's sysfs interface is disabled.
+ */
+static inline bool led_sysfs_is_disabled(struct led_classdev *led_cdev)
+{
+	return led_cdev->flags & LED_SYSFS_DISABLE;
+}
+
 /*
  * LED Triggers
  */
-- 
1.7.9.5

Re: [PATCH/RFC v6 1/3] leds: implement sysfs interface locking mechanism

[Bryan Wu]

On Mon, Sep 22, 2014 at 8:21 AM, Jacek Anaszewski
<j.anaszewski@samsung.com> wrote:
> Add a mechanism for locking LED subsystem sysfs interface.
> This patch prepares ground for addition of LED Flash Class
> extension, whose API will be integrated with V4L2 Flash API.
> Such a fusion enforces introducing a locking scheme, which
> will secure consistent access to the LED Flash Class device.
>
> The mechanism being introduced allows for disabling LED
> subsystem sysfs interface by calling led_sysfs_disable function
> and enabling it by calling led_sysfs_enable. The functions
> alter the LED_SYSFS_DISABLE flag state and must be called
> under mutex lock. The state of the lock is checked with use
> of led_sysfs_is_disabled function. Such a design allows for
> providing immediate feedback to the user space on whether
> the LED Flash Class device is available or is under V4L2 Flash
> sub-device control.
>

I'm good with this and will merge it soon.

Thanks,
-Bryan

> Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
> Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
> Cc: Bryan Wu <cooloney@gmail.com>
> Cc: Richard Purdie <rpurdie@rpsys.net>
> ---
>  drivers/leds/led-class.c    |   19 ++++++++++++++++---
>  drivers/leds/led-core.c     |   18 ++++++++++++++++++
>  drivers/leds/led-triggers.c |   16 +++++++++++++---
>  include/linux/leds.h        |   32 ++++++++++++++++++++++++++++++++
>  4 files changed, 79 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index 2e124aa2..a39ca8f 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -39,17 +39,27 @@ static ssize_t brightness_store(struct device *dev,
>  {
>         struct led_classdev *led_cdev = dev_get_drvdata(dev);
>         unsigned long state;
> -       ssize_t ret = -EINVAL;
> +       ssize_t ret;
> +
> +       mutex_lock(&led_cdev->led_access);
> +
> +       if (led_sysfs_is_disabled(led_cdev)) {
> +               ret = -EBUSY;
> +               goto unlock;
> +       }
>
>         ret = kstrtoul(buf, 10, &state);
>         if (ret)
> -               return ret;
> +               goto unlock;
>
>         if (state == LED_OFF)
>                 led_trigger_remove(led_cdev);
>         __led_set_brightness(led_cdev, state);
>
> -       return size;
> +       ret = size;
> +unlock:
> +       mutex_unlock(&led_cdev->led_access);
> +       return ret;
>  }
>  static DEVICE_ATTR_RW(brightness);
>
> @@ -213,6 +223,7 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
>  #ifdef CONFIG_LEDS_TRIGGERS
>         init_rwsem(&led_cdev->trigger_lock);
>  #endif
> +       mutex_init(&led_cdev->led_access);
>         /* add to the list of leds */
>         down_write(&leds_list_lock);
>         list_add_tail(&led_cdev->node, &leds_list);
> @@ -266,6 +277,8 @@ void led_classdev_unregister(struct led_classdev *led_cdev)
>         down_write(&leds_list_lock);
>         list_del(&led_cdev->node);
>         up_write(&leds_list_lock);
> +
> +       mutex_destroy(&led_cdev->led_access);
>  }
>  EXPORT_SYMBOL_GPL(led_classdev_unregister);
>
> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> index 0d15aa9..cca86ab 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -142,3 +142,21 @@ int led_update_brightness(struct led_classdev *led_cdev)
>         return ret;
>  }
>  EXPORT_SYMBOL(led_update_brightness);
> +
> +/* Caller must ensure led_cdev->led_access held */
> +void led_sysfs_disable(struct led_classdev *led_cdev)
> +{
> +       lockdep_assert_held(&led_cdev->led_access);
> +
> +       led_cdev->flags |= LED_SYSFS_DISABLE;
> +}
> +EXPORT_SYMBOL_GPL(led_sysfs_disable);
> +
> +/* Caller must ensure led_cdev->led_access held */
> +void led_sysfs_enable(struct led_classdev *led_cdev)
> +{
> +       lockdep_assert_held(&led_cdev->led_access);
> +
> +       led_cdev->flags &= ~LED_SYSFS_DISABLE;
> +}
> +EXPORT_SYMBOL_GPL(led_sysfs_enable);
> diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
> index c3734f1..e8b1120 100644
> --- a/drivers/leds/led-triggers.c
> +++ b/drivers/leds/led-triggers.c
> @@ -37,6 +37,14 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
>         char trigger_name[TRIG_NAME_MAX];
>         struct led_trigger *trig;
>         size_t len;
> +       int ret = count;
> +
> +       mutex_lock(&led_cdev->led_access);
> +
> +       if (led_sysfs_is_disabled(led_cdev)) {
> +               ret = -EBUSY;
> +               goto unlock;
> +       }
>
>         trigger_name[sizeof(trigger_name) - 1] = '\0';
>         strncpy(trigger_name, buf, sizeof(trigger_name) - 1);
> @@ -47,7 +55,7 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
>
>         if (!strcmp(trigger_name, "none")) {
>                 led_trigger_remove(led_cdev);
> -               return count;
> +               goto unlock;
>         }
>
>         down_read(&triggers_list_lock);
> @@ -58,12 +66,14 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
>                         up_write(&led_cdev->trigger_lock);
>
>                         up_read(&triggers_list_lock);
> -                       return count;
> +                       goto unlock;
>                 }
>         }
>         up_read(&triggers_list_lock);
>
> -       return -EINVAL;
> +unlock:
> +       mutex_unlock(&led_cdev->led_access);
> +       return ret;
>  }
>  EXPORT_SYMBOL_GPL(led_trigger_store);
>
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index f8b2f58..44c8a98 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -13,6 +13,7 @@
>  #define __LINUX_LEDS_H_INCLUDED
>
>  #include <linux/list.h>
> +#include <linux/mutex.h>
>  #include <linux/rwsem.h>
>  #include <linux/spinlock.h>
>  #include <linux/timer.h>
> @@ -42,6 +43,7 @@ struct led_classdev {
>  #define LED_BLINK_ONESHOT      (1 << 17)
>  #define LED_BLINK_ONESHOT_STOP (1 << 18)
>  #define LED_BLINK_INVERT       (1 << 19)
> +#define LED_SYSFS_DISABLE      (1 << 20)
>
>         /* Set LED brightness level */
>         /* Must not sleep, use a workqueue if needed */
> @@ -85,6 +87,9 @@ struct led_classdev {
>         /* true if activated - deactivate routine uses it to do cleanup */
>         bool                    activated;
>  #endif
> +
> +       /* Ensures consistent access to the LED Flash Class device */
> +       struct mutex            led_access;
>  };
>
>  extern int led_classdev_register(struct device *parent,
> @@ -151,6 +156,33 @@ extern void led_set_brightness(struct led_classdev *led_cdev,
>   */
>  extern int led_update_brightness(struct led_classdev *led_cdev);
>
> +/**
> + * led_sysfs_disable - disable LED sysfs interface
> + * @led_cdev: the LED to set
> + *
> + * Disable the led_cdev's sysfs interface.
> + */
> +extern void led_sysfs_disable(struct led_classdev *led_cdev);
> +
> +/**
> + * led_sysfs_enable - enable LED sysfs interface
> + * @led_cdev: the LED to set
> + *
> + * Enable the led_cdev's sysfs interface.
> + */
> +extern void led_sysfs_enable(struct led_classdev *led_cdev);
> +
> +/**
> + * led_sysfs_is_disabled - check if LED sysfs interface is disabled
> + * @led_cdev: the LED to query
> + *
> + * Returns: true if the led_cdev's sysfs interface is disabled.
> + */
> +static inline bool led_sysfs_is_disabled(struct led_classdev *led_cdev)
> +{
> +       return led_cdev->flags & LED_SYSFS_DISABLE;
> +}
> +
>  /*
>   * LED Triggers
>   */
> --
> 1.7.9.5
>

Re: [PATCH/RFC v6 1/3] leds: implement sysfs interface locking mechanism

[Bryan Wu]

On Mon, Oct 20, 2014 at 6:01 PM, Bryan Wu <cooloney@gmail.com> wrote:
> On Mon, Sep 22, 2014 at 8:21 AM, Jacek Anaszewski
> <j.anaszewski@samsung.com> wrote:
>> Add a mechanism for locking LED subsystem sysfs interface.
>> This patch prepares ground for addition of LED Flash Class
>> extension, whose API will be integrated with V4L2 Flash API.
>> Such a fusion enforces introducing a locking scheme, which
>> will secure consistent access to the LED Flash Class device.
>>
>> The mechanism being introduced allows for disabling LED
>> subsystem sysfs interface by calling led_sysfs_disable function
>> and enabling it by calling led_sysfs_enable. The functions
>> alter the LED_SYSFS_DISABLE flag state and must be called
>> under mutex lock. The state of the lock is checked with use
>> of led_sysfs_is_disabled function. Such a design allows for
>> providing immediate feedback to the user space on whether
>> the LED Flash Class device is available or is under V4L2 Flash
>> sub-device control.
>>
>
> I'm good with this and will merge it soon.
>

Just merged it into my tree.

Thanks,
-Bryan


>> Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
>> Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
>> Cc: Bryan Wu <cooloney@gmail.com>
>> Cc: Richard Purdie <rpurdie@rpsys.net>
>> ---
>>  drivers/leds/led-class.c    |   19 ++++++++++++++++---
>>  drivers/leds/led-core.c     |   18 ++++++++++++++++++
>>  drivers/leds/led-triggers.c |   16 +++++++++++++---
>>  include/linux/leds.h        |   32 ++++++++++++++++++++++++++++++++
>>  4 files changed, 79 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
>> index 2e124aa2..a39ca8f 100644
>> --- a/drivers/leds/led-class.c
>> +++ b/drivers/leds/led-class.c
>> @@ -39,17 +39,27 @@ static ssize_t brightness_store(struct device *dev,
>>  {
>>         struct led_classdev *led_cdev = dev_get_drvdata(dev);
>>         unsigned long state;
>> -       ssize_t ret = -EINVAL;
>> +       ssize_t ret;
>> +
>> +       mutex_lock(&led_cdev->led_access);
>> +
>> +       if (led_sysfs_is_disabled(led_cdev)) {
>> +               ret = -EBUSY;
>> +               goto unlock;
>> +       }
>>
>>         ret = kstrtoul(buf, 10, &state);
>>         if (ret)
>> -               return ret;
>> +               goto unlock;
>>
>>         if (state == LED_OFF)
>>                 led_trigger_remove(led_cdev);
>>         __led_set_brightness(led_cdev, state);
>>
>> -       return size;
>> +       ret = size;
>> +unlock:
>> +       mutex_unlock(&led_cdev->led_access);
>> +       return ret;
>>  }
>>  static DEVICE_ATTR_RW(brightness);
>>
>> @@ -213,6 +223,7 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
>>  #ifdef CONFIG_LEDS_TRIGGERS
>>         init_rwsem(&led_cdev->trigger_lock);
>>  #endif
>> +       mutex_init(&led_cdev->led_access);
>>         /* add to the list of leds */
>>         down_write(&leds_list_lock);
>>         list_add_tail(&led_cdev->node, &leds_list);
>> @@ -266,6 +277,8 @@ void led_classdev_unregister(struct led_classdev *led_cdev)
>>         down_write(&leds_list_lock);
>>         list_del(&led_cdev->node);
>>         up_write(&leds_list_lock);
>> +
>> +       mutex_destroy(&led_cdev->led_access);
>>  }
>>  EXPORT_SYMBOL_GPL(led_classdev_unregister);
>>
>> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
>> index 0d15aa9..cca86ab 100644
>> --- a/drivers/leds/led-core.c
>> +++ b/drivers/leds/led-core.c
>> @@ -142,3 +142,21 @@ int led_update_brightness(struct led_classdev *led_cdev)
>>         return ret;
>>  }
>>  EXPORT_SYMBOL(led_update_brightness);
>> +
>> +/* Caller must ensure led_cdev->led_access held */
>> +void led_sysfs_disable(struct led_classdev *led_cdev)
>> +{
>> +       lockdep_assert_held(&led_cdev->led_access);
>> +
>> +       led_cdev->flags |= LED_SYSFS_DISABLE;
>> +}
>> +EXPORT_SYMBOL_GPL(led_sysfs_disable);
>> +
>> +/* Caller must ensure led_cdev->led_access held */
>> +void led_sysfs_enable(struct led_classdev *led_cdev)
>> +{
>> +       lockdep_assert_held(&led_cdev->led_access);
>> +
>> +       led_cdev->flags &= ~LED_SYSFS_DISABLE;
>> +}
>> +EXPORT_SYMBOL_GPL(led_sysfs_enable);
>> diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
>> index c3734f1..e8b1120 100644
>> --- a/drivers/leds/led-triggers.c
>> +++ b/drivers/leds/led-triggers.c
>> @@ -37,6 +37,14 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
>>         char trigger_name[TRIG_NAME_MAX];
>>         struct led_trigger *trig;
>>         size_t len;
>> +       int ret = count;
>> +
>> +       mutex_lock(&led_cdev->led_access);
>> +
>> +       if (led_sysfs_is_disabled(led_cdev)) {
>> +               ret = -EBUSY;
>> +               goto unlock;
>> +       }
>>
>>         trigger_name[sizeof(trigger_name) - 1] = '\0';
>>         strncpy(trigger_name, buf, sizeof(trigger_name) - 1);
>> @@ -47,7 +55,7 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
>>
>>         if (!strcmp(trigger_name, "none")) {
>>                 led_trigger_remove(led_cdev);
>> -               return count;
>> +               goto unlock;
>>         }
>>
>>         down_read(&triggers_list_lock);
>> @@ -58,12 +66,14 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
>>                         up_write(&led_cdev->trigger_lock);
>>
>>                         up_read(&triggers_list_lock);
>> -                       return count;
>> +                       goto unlock;
>>                 }
>>         }
>>         up_read(&triggers_list_lock);
>>
>> -       return -EINVAL;
>> +unlock:
>> +       mutex_unlock(&led_cdev->led_access);
>> +       return ret;
>>  }
>>  EXPORT_SYMBOL_GPL(led_trigger_store);
>>
>> diff --git a/include/linux/leds.h b/include/linux/leds.h
>> index f8b2f58..44c8a98 100644
>> --- a/include/linux/leds.h
>> +++ b/include/linux/leds.h
>> @@ -13,6 +13,7 @@
>>  #define __LINUX_LEDS_H_INCLUDED
>>
>>  #include <linux/list.h>
>> +#include <linux/mutex.h>
>>  #include <linux/rwsem.h>
>>  #include <linux/spinlock.h>
>>  #include <linux/timer.h>
>> @@ -42,6 +43,7 @@ struct led_classdev {
>>  #define LED_BLINK_ONESHOT      (1 << 17)
>>  #define LED_BLINK_ONESHOT_STOP (1 << 18)
>>  #define LED_BLINK_INVERT       (1 << 19)
>> +#define LED_SYSFS_DISABLE      (1 << 20)
>>
>>         /* Set LED brightness level */
>>         /* Must not sleep, use a workqueue if needed */
>> @@ -85,6 +87,9 @@ struct led_classdev {
>>         /* true if activated - deactivate routine uses it to do cleanup */
>>         bool                    activated;
>>  #endif
>> +
>> +       /* Ensures consistent access to the LED Flash Class device */
>> +       struct mutex            led_access;
>>  };
>>
>>  extern int led_classdev_register(struct device *parent,
>> @@ -151,6 +156,33 @@ extern void led_set_brightness(struct led_classdev *led_cdev,
>>   */
>>  extern int led_update_brightness(struct led_classdev *led_cdev);
>>
>> +/**
>> + * led_sysfs_disable - disable LED sysfs interface
>> + * @led_cdev: the LED to set
>> + *
>> + * Disable the led_cdev's sysfs interface.
>> + */
>> +extern void led_sysfs_disable(struct led_classdev *led_cdev);
>> +
>> +/**
>> + * led_sysfs_enable - enable LED sysfs interface
>> + * @led_cdev: the LED to set
>> + *
>> + * Enable the led_cdev's sysfs interface.
>> + */
>> +extern void led_sysfs_enable(struct led_classdev *led_cdev);
>> +
>> +/**
>> + * led_sysfs_is_disabled - check if LED sysfs interface is disabled
>> + * @led_cdev: the LED to query
>> + *
>> + * Returns: true if the led_cdev's sysfs interface is disabled.
>> + */
>> +static inline bool led_sysfs_is_disabled(struct led_classdev *led_cdev)
>> +{
>> +       return led_cdev->flags & LED_SYSFS_DISABLE;
>> +}
>> +
>>  /*
>>   * LED Triggers
>>   */
>> --
>> 1.7.9.5
>>

[PATCH/RFC v6 2/3] leds: add API for setting torch brightness

[Jacek Anaszewski]

This patch prepares ground for addition of LED Flash Class extension to
the LED subsystem. Since turning the torch on must have guaranteed
immediate effect the brightness_set op can't be used for it. Drivers must
schedule a work queue task in this op to be compatible with led-triggers,
which call brightess_set from timer irqs. In order to address this
limitation a torch_brightness_set op and led_set_torch_brightness API
is introduced. Setting brightness sysfs attribute will result in calling
brightness_set op for LED Class devices and torch_brightness_set op for
LED Flash Class devices, whereas triggers will still call brightness
op in both cases.

Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Bryan Wu <cooloney@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
---
 drivers/leds/led-class.c |    9 +++++++--
 drivers/leds/led-core.c  |   14 ++++++++++++++
 include/linux/leds.h     |   21 +++++++++++++++++++++
 3 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index a39ca8f..5a11a07 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -54,9 +54,14 @@ static ssize_t brightness_store(struct device *dev,
 
 	if (state == LED_OFF)
 		led_trigger_remove(led_cdev);
-	__led_set_brightness(led_cdev, state);
 
-	ret = size;
+	if (led_cdev->flags & LED_DEV_CAP_TORCH)
+		ret = led_set_torch_brightness(led_cdev, state);
+	else
+		__led_set_brightness(led_cdev, state);
+
+	if (!ret)
+		ret = size;
 unlock:
 	mutex_unlock(&led_cdev->led_access);
 	return ret;
diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index cca86ab..c6d8288 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -143,6 +143,20 @@ int led_update_brightness(struct led_classdev *led_cdev)
 }
 EXPORT_SYMBOL(led_update_brightness);
 
+int led_set_torch_brightness(struct led_classdev *led_cdev,
+				enum led_brightness brightness)
+{
+	int ret = 0;
+
+	led_cdev->brightness = min(brightness, led_cdev->max_brightness);
+
+	if (!(led_cdev->flags & LED_SUSPENDED))
+		ret = led_cdev->torch_brightness_set(led_cdev,
+						     led_cdev->brightness);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(led_set_torch_brightness);
+
 /* Caller must ensure led_cdev->led_access held */
 void led_sysfs_disable(struct led_classdev *led_cdev)
 {
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 44c8a98..bc2a570 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -44,11 +44,21 @@ struct led_classdev {
 #define LED_BLINK_ONESHOT_STOP	(1 << 18)
 #define LED_BLINK_INVERT	(1 << 19)
 #define LED_SYSFS_DISABLE	(1 << 20)
+#define LED_DEV_CAP_TORCH	(1 << 21)
 
 	/* Set LED brightness level */
 	/* Must not sleep, use a workqueue if needed */
 	void		(*brightness_set)(struct led_classdev *led_cdev,
 					  enum led_brightness brightness);
+	/*
+	 * Set LED brightness immediately - it is required for flash led
+	 * devices as they require setting torch brightness to have immediate
+	 * effect. brightness_set op cannot be used for this purpose because
+	 * the led drivers schedule a work queue task in it to allow for
+	 * being called from led-triggers, i.e. from the timer irq context.
+	 */
+	int		(*torch_brightness_set)(struct led_classdev *led_cdev,
+					enum led_brightness brightness);
 	/* Get LED brightness level */
 	enum led_brightness (*brightness_get)(struct led_classdev *led_cdev);
 
@@ -157,6 +167,17 @@ extern void led_set_brightness(struct led_classdev *led_cdev,
 extern int led_update_brightness(struct led_classdev *led_cdev);
 
 /**
+ * led_set_torch_brightness - set torch LED brightness
+ * @led_cdev: the LED to set
+ * @brightness: the brightness to set it to
+ *
+ * Returns: 0 on success or negative error value on failure
+ *
+ * Set a torch LED's brightness.
+ */
+extern int led_set_torch_brightness(struct led_classdev *led_cdev,
+					enum led_brightness brightness);
+/**
  * led_sysfs_disable - disable LED sysfs interface
  * @led_cdev: the LED to set
  *
-- 
1.7.9.5

Re: [PATCH/RFC v6 2/3] leds: add API for setting torch brightness

[Bryan Wu]

On Mon, Sep 22, 2014 at 8:21 AM, Jacek Anaszewski
<j.anaszewski@samsung.com> wrote:
> This patch prepares ground for addition of LED Flash Class extension to
> the LED subsystem. Since turning the torch on must have guaranteed
> immediate effect the brightness_set op can't be used for it. Drivers must
> schedule a work queue task in this op to be compatible with led-triggers,
> which call brightess_set from timer irqs. In order to address this
> limitation a torch_brightness_set op and led_set_torch_brightness API
> is introduced. Setting brightness sysfs attribute will result in calling
> brightness_set op for LED Class devices and torch_brightness_set op for
> LED Flash Class devices, whereas triggers will still call brightness
> op in both cases.
>

Although this torch API is for torch, but I think we can make it more
generic and other use case can benefit from this change.

What about this?

Add 2 flags:
1. SET_BRIGHTNESS_ASYNC
2. SET_BRIGHTNESS_SYNC

Then move old API to
__led_set_brightness(led_cdev, state);
led_set_brightness_async();

And add a new API like
led_set_bightness_sync();

Then for torch use case, we use led_set_brightness_sync() API.

-Bryan

> Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
> Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
> Cc: Bryan Wu <cooloney@gmail.com>
> Cc: Richard Purdie <rpurdie@rpsys.net>
> ---
>  drivers/leds/led-class.c |    9 +++++++--
>  drivers/leds/led-core.c  |   14 ++++++++++++++
>  include/linux/leds.h     |   21 +++++++++++++++++++++
>  3 files changed, 42 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index a39ca8f..5a11a07 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -54,9 +54,14 @@ static ssize_t brightness_store(struct device *dev,
>
>         if (state == LED_OFF)
>                 led_trigger_remove(led_cdev);
> -       __led_set_brightness(led_cdev, state);
>
> -       ret = size;
> +       if (led_cdev->flags & LED_DEV_CAP_TORCH)
> +               ret = led_set_torch_brightness(led_cdev, state);
> +       else
> +               __led_set_brightness(led_cdev, state);
> +
> +       if (!ret)
> +               ret = size;
>  unlock:
>         mutex_unlock(&led_cdev->led_access);
>         return ret;
> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> index cca86ab..c6d8288 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -143,6 +143,20 @@ int led_update_brightness(struct led_classdev *led_cdev)
>  }
>  EXPORT_SYMBOL(led_update_brightness);
>
> +int led_set_torch_brightness(struct led_classdev *led_cdev,
> +                               enum led_brightness brightness)
> +{
> +       int ret = 0;
> +
> +       led_cdev->brightness = min(brightness, led_cdev->max_brightness);
> +
> +       if (!(led_cdev->flags & LED_SUSPENDED))
> +               ret = led_cdev->torch_brightness_set(led_cdev,
> +                                                    led_cdev->brightness);
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(led_set_torch_brightness);
> +
>  /* Caller must ensure led_cdev->led_access held */
>  void led_sysfs_disable(struct led_classdev *led_cdev)
>  {
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 44c8a98..bc2a570 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -44,11 +44,21 @@ struct led_classdev {
>  #define LED_BLINK_ONESHOT_STOP (1 << 18)
>  #define LED_BLINK_INVERT       (1 << 19)
>  #define LED_SYSFS_DISABLE      (1 << 20)
> +#define LED_DEV_CAP_TORCH      (1 << 21)
>
>         /* Set LED brightness level */
>         /* Must not sleep, use a workqueue if needed */
>         void            (*brightness_set)(struct led_classdev *led_cdev,
>                                           enum led_brightness brightness);
> +       /*
> +        * Set LED brightness immediately - it is required for flash led
> +        * devices as they require setting torch brightness to have immediate
> +        * effect. brightness_set op cannot be used for this purpose because
> +        * the led drivers schedule a work queue task in it to allow for
> +        * being called from led-triggers, i.e. from the timer irq context.
> +        */
> +       int             (*torch_brightness_set)(struct led_classdev *led_cdev,
> +                                       enum led_brightness brightness);
>         /* Get LED brightness level */
>         enum led_brightness (*brightness_get)(struct led_classdev *led_cdev);
>
> @@ -157,6 +167,17 @@ extern void led_set_brightness(struct led_classdev *led_cdev,
>  extern int led_update_brightness(struct led_classdev *led_cdev);
>
>  /**
> + * led_set_torch_brightness - set torch LED brightness
> + * @led_cdev: the LED to set
> + * @brightness: the brightness to set it to
> + *
> + * Returns: 0 on success or negative error value on failure
> + *
> + * Set a torch LED's brightness.
> + */
> +extern int led_set_torch_brightness(struct led_classdev *led_cdev,
> +                                       enum led_brightness brightness);
> +/**
>   * led_sysfs_disable - disable LED sysfs interface
>   * @led_cdev: the LED to set
>   *
> --
> 1.7.9.5
>

[PATCH/RFC v6 3/3] leds: Add LED Flash Class wrapper to LED subsystem

[Jacek Anaszewski]

Some LED devices support two operation modes - torch and flash.
This patch provides support for flash LED devices in the LED subsystem
by introducing new sysfs attributes and kernel internal interface.
The attributes being introduced are: flash_brightness, flash_strobe,
flash_timeout, max_flash_timeout, max_flash_brightness, flash_fault,
indicator_brightness and  max_indicator_brightness. All the flash
related features are placed in a separate module.

The modifications aim to be compatible with V4L2 framework requirements
related to the flash devices management. The design assumes that V4L2
sub-device can take of the LED class device control and communicate
with it through the kernel internal interface. When V4L2 Flash sub-device
file is opened, the LED class device sysfs interface is made
unavailable.

Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Bryan Wu <cooloney@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
---
 drivers/leds/Kconfig            |   11 +
 drivers/leds/Makefile           |    1 +
 drivers/leds/led-class-flash.c  |  557 +++++++++++++++++++++++++++++++++++++++
 drivers/leds/led-class.c        |    4 +
 include/linux/led-class-flash.h |  238 +++++++++++++++++
 include/linux/leds.h            |    3 +
 6 files changed, 814 insertions(+)
 create mode 100644 drivers/leds/led-class-flash.c
 create mode 100644 include/linux/led-class-flash.h

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 8c96e2d..3c58021 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -22,6 +22,17 @@ config LEDS_CLASS
 	  This option enables the led sysfs class in /sys/class/leds.  You'll
 	  need this to do anything useful with LEDs.  If unsure, say N.
 
+config LEDS_CLASS_FLASH
+	tristate "LED Flash Class Support"
+	depends on LEDS_CLASS
+	depends on OF
+	help
+	  This option enables the flash led sysfs class in /sys/class/leds.
+	  It wrapps LED Class and adds flash LEDs specific sysfs attributes
+	  and kernel internal API to it. You'll need this to provide support
+	  for the flash related features of a LED device. It can be built
+	  as a module.
+
 comment "LED drivers"
 
 config LEDS_88PM860X
diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index d8cc5f2..9238b8a 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -2,6 +2,7 @@
 # LED Core
 obj-$(CONFIG_NEW_LEDS)			+= led-core.o
 obj-$(CONFIG_LEDS_CLASS)		+= led-class.o
+obj-$(CONFIG_LEDS_CLASS_FLASH)		+= led-class-flash.o
 obj-$(CONFIG_LEDS_TRIGGERS)		+= led-triggers.o
 
 # LED Platform Drivers
diff --git a/drivers/leds/led-class-flash.c b/drivers/leds/led-class-flash.c
new file mode 100644
index 0000000..f1ba539
--- /dev/null
+++ b/drivers/leds/led-class-flash.c
@@ -0,0 +1,557 @@
+/*
+ * LED Flash Class interface
+ *
+ * Copyright (C) 2014 Samsung Electronics Co., Ltd.
+ * Author: Jacek Anaszewski <j.anaszewski@samsung.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/leds.h>
+#include <linux/led-class-flash.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include "leds.h"
+
+#define has_flash_op(flash, op)				\
+	(flash && flash->ops->op)
+
+#define call_flash_op(flash, op, args...)		\
+	((has_flash_op(flash, op)) ?			\
+			(flash->ops->op(flash, args)) :	\
+			-EINVAL)
+
+static ssize_t flash_brightness_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+	unsigned long state;
+	ssize_t ret;
+
+	mutex_lock(&led_cdev->led_access);
+
+	if (led_sysfs_is_disabled(led_cdev)) {
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	ret = kstrtoul(buf, 10, &state);
+	if (ret)
+		goto unlock;
+
+	ret = led_set_flash_brightness(flash, state);
+	if (ret < 0)
+		goto unlock;
+
+	ret = size;
+unlock:
+	mutex_unlock(&led_cdev->led_access);
+	return ret;
+}
+
+static ssize_t flash_brightness_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+
+	/* no lock needed for this */
+	led_update_flash_brightness(flash);
+
+	return sprintf(buf, "%u\n", flash->brightness.val);
+}
+static DEVICE_ATTR_RW(flash_brightness);
+
+static ssize_t max_flash_brightness_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+
+	return sprintf(buf, "%u\n", flash->brightness.max);
+}
+static DEVICE_ATTR_RO(max_flash_brightness);
+
+static ssize_t indicator_brightness_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+	unsigned long state;
+	ssize_t ret;
+
+	mutex_lock(&led_cdev->led_access);
+
+	if (led_sysfs_is_disabled(led_cdev)) {
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	ret = kstrtoul(buf, 10, &state);
+	if (ret)
+		goto unlock;
+
+	ret = led_set_indicator_brightness(flash, state);
+	if (ret < 0)
+		goto unlock;
+
+	ret = size;
+unlock:
+	mutex_unlock(&led_cdev->led_access);
+	return ret;
+}
+
+static ssize_t indicator_brightness_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+
+	/* no lock needed for this */
+	led_update_indicator_brightness(flash);
+
+	return sprintf(buf, "%u\n", flash->indicator_brightness->val);
+}
+static DEVICE_ATTR_RW(indicator_brightness);
+
+static ssize_t max_indicator_brightness_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+
+	return sprintf(buf, "%u\n", flash->indicator_brightness->max);
+}
+static DEVICE_ATTR_RO(max_indicator_brightness);
+
+static ssize_t flash_strobe_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+	unsigned long state;
+	ssize_t ret = -EINVAL;
+
+	mutex_lock(&led_cdev->led_access);
+
+	if (led_sysfs_is_disabled(led_cdev)) {
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	ret = kstrtoul(buf, 10, &state);
+	if (ret)
+		goto unlock;
+
+	if (state < 0 || state > 1) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	ret = led_set_flash_strobe(flash, state);
+	if (ret < 0)
+		goto unlock;
+	ret = size;
+unlock:
+	mutex_unlock(&led_cdev->led_access);
+	return ret;
+}
+
+static ssize_t flash_strobe_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+	bool state;
+	int ret;
+
+	/* no lock needed for this */
+	ret = led_get_flash_strobe(flash, &state);
+	if (ret < 0)
+		return ret;
+
+	return sprintf(buf, "%u\n", state);
+}
+static DEVICE_ATTR_RW(flash_strobe);
+
+static ssize_t flash_timeout_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+	unsigned long flash_timeout;
+	ssize_t ret;
+
+	mutex_lock(&led_cdev->led_access);
+
+	if (led_sysfs_is_disabled(led_cdev)) {
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	ret = kstrtoul(buf, 10, &flash_timeout);
+	if (ret)
+		goto unlock;
+
+	ret = led_set_flash_timeout(flash, flash_timeout);
+	if (ret < 0)
+		goto unlock;
+
+	ret = size;
+unlock:
+	mutex_unlock(&led_cdev->led_access);
+	return ret;
+}
+
+static ssize_t flash_timeout_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+
+	return sprintf(buf, "%u\n", flash->timeout.val);
+}
+static DEVICE_ATTR_RW(flash_timeout);
+
+static ssize_t max_flash_timeout_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+
+	return sprintf(buf, "%u\n", flash->timeout.max);
+}
+static DEVICE_ATTR_RO(max_flash_timeout);
+
+static ssize_t flash_fault_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+	u32 fault;
+	int ret;
+
+	ret = led_get_flash_fault(flash, &fault);
+	if (ret < 0)
+		return -EINVAL;
+
+	return sprintf(buf, "0x%8.8x\n", fault);
+}
+static DEVICE_ATTR_RO(flash_fault);
+
+static struct attribute *led_flash_strobe_attrs[] = {
+	&dev_attr_flash_strobe.attr,
+	NULL,
+};
+
+static struct attribute *led_flash_indicator_attrs[] = {
+	&dev_attr_indicator_brightness.attr,
+	&dev_attr_max_indicator_brightness.attr,
+	NULL,
+};
+
+static struct attribute *led_flash_timeout_attrs[] = {
+	&dev_attr_flash_timeout.attr,
+	&dev_attr_max_flash_timeout.attr,
+	NULL,
+};
+
+static struct attribute *led_flash_brightness_attrs[] = {
+	&dev_attr_flash_brightness.attr,
+	&dev_attr_max_flash_brightness.attr,
+	NULL,
+};
+
+static struct attribute *led_flash_fault_attrs[] = {
+	&dev_attr_flash_fault.attr,
+	NULL,
+};
+
+static struct attribute_group led_flash_strobe_group = {
+	.attrs = led_flash_strobe_attrs,
+};
+
+static struct attribute_group led_flash_brightness_group = {
+	.attrs = led_flash_brightness_attrs,
+};
+
+static struct attribute_group led_flash_timeout_group = {
+	.attrs = led_flash_timeout_attrs,
+};
+
+static struct attribute_group led_flash_indicator_group = {
+	.attrs = led_flash_indicator_attrs,
+};
+
+static struct attribute_group led_flash_fault_group = {
+	.attrs = led_flash_fault_attrs,
+};
+
+static void led_flash_resume(struct led_classdev *led_cdev)
+{
+	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
+
+	call_flash_op(flash, flash_brightness_set, flash->brightness.val);
+	call_flash_op(flash, timeout_set, flash->timeout.val);
+	call_flash_op(flash, indicator_brightness_set,
+				flash->indicator_brightness->val);
+}
+
+static void led_flash_remove_sysfs_groups(struct led_classdev_flash *flash)
+{
+	struct led_classdev *led_cdev = &flash->led_cdev;
+	int i;
+
+	for (i = 0; i < LED_FLASH_MAX_SYSFS_GROUPS; ++i)
+		if (flash->sysfs_groups[i])
+			sysfs_remove_group(&led_cdev->dev->kobj,
+						flash->sysfs_groups[i]);
+}
+
+static int led_flash_create_sysfs_groups(struct led_classdev_flash *flash)
+{
+	struct led_classdev *led_cdev = &flash->led_cdev;
+	const struct led_flash_ops *ops = flash->ops;
+	int ret, num_sysfs_groups = 0;
+
+	memset(flash->sysfs_groups, 0, sizeof(*flash->sysfs_groups) *
+						LED_FLASH_MAX_SYSFS_GROUPS);
+
+	ret = sysfs_create_group(&led_cdev->dev->kobj, &led_flash_strobe_group);
+	if (ret < 0)
+		goto err_create_group;
+	flash->sysfs_groups[num_sysfs_groups++] = &led_flash_strobe_group;
+
+	if (flash->indicator_brightness) {
+		ret = sysfs_create_group(&led_cdev->dev->kobj,
+					&led_flash_indicator_group);
+		if (ret < 0)
+			goto err_create_group;
+		flash->sysfs_groups[num_sysfs_groups++] =
+					&led_flash_indicator_group;
+	}
+
+	if (ops->flash_brightness_set) {
+		ret = sysfs_create_group(&led_cdev->dev->kobj,
+					&led_flash_brightness_group);
+		if (ret < 0)
+			goto err_create_group;
+		flash->sysfs_groups[num_sysfs_groups++] =
+					&led_flash_brightness_group;
+	}
+
+	if (ops->timeout_set) {
+		ret = sysfs_create_group(&led_cdev->dev->kobj,
+					&led_flash_timeout_group);
+		if (ret < 0)
+			goto err_create_group;
+		flash->sysfs_groups[num_sysfs_groups++] =
+					&led_flash_timeout_group;
+	}
+
+	if (ops->fault_get) {
+		ret = sysfs_create_group(&led_cdev->dev->kobj,
+					&led_flash_fault_group);
+		if (ret < 0)
+			goto err_create_group;
+		flash->sysfs_groups[num_sysfs_groups++] =
+					&led_flash_fault_group;
+	}
+
+	return 0;
+
+err_create_group:
+	led_flash_remove_sysfs_groups(flash);
+	return ret;
+}
+
+int led_classdev_flash_register(struct device *parent,
+				struct led_classdev_flash *flash,
+				struct device_node *node)
+{
+	struct led_classdev *led_cdev;
+	const struct led_flash_ops *ops;
+	int ret = -EINVAL;
+
+	if (!flash)
+		return -EINVAL;
+
+	led_cdev = &flash->led_cdev;
+
+	/* Torch capability is default for every LED Flash Class device */
+	led_cdev->flags |= LED_DEV_CAP_TORCH;
+
+	if (led_cdev->flags & LED_DEV_CAP_FLASH) {
+		if (!led_cdev->torch_brightness_set)
+			return -EINVAL;
+
+		ops = flash->ops;
+		if (!ops || !ops->strobe_set)
+			return -EINVAL;
+
+		if ((led_cdev->flags & LED_DEV_CAP_INDICATOR) &&
+		    (!flash->indicator_brightness ||
+		     !ops->indicator_brightness_set))
+			return -EINVAL;
+
+		led_cdev->flash_resume = led_flash_resume;
+	}
+
+	/* Register led class device */
+	ret = led_classdev_register(parent, led_cdev);
+	if (ret < 0)
+		return -EINVAL;
+
+	/* Create flash led specific sysfs attributes */
+	ret = led_flash_create_sysfs_groups(flash);
+	if (ret < 0)
+		goto err_create_sysfs_groups;
+
+	return 0;
+
+err_create_sysfs_groups:
+	led_classdev_unregister(led_cdev);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(led_classdev_flash_register);
+
+void led_classdev_flash_unregister(struct led_classdev_flash *flash)
+{
+	if (!flash)
+		return;
+
+	led_flash_remove_sysfs_groups(flash);
+	led_classdev_unregister(&flash->led_cdev);
+}
+EXPORT_SYMBOL_GPL(led_classdev_flash_unregister);
+
+int led_set_flash_strobe(struct led_classdev_flash *flash, bool state)
+{
+	return call_flash_op(flash, strobe_set, state);
+}
+EXPORT_SYMBOL_GPL(led_set_flash_strobe);
+
+int led_get_flash_strobe(struct led_classdev_flash *flash, bool *state)
+{
+	return call_flash_op(flash, strobe_get, state);
+}
+EXPORT_SYMBOL_GPL(led_get_flash_strobe);
+
+static void led_clamp_align(struct led_flash_setting *s)
+{
+	u32 v, offset;
+
+	v = s->val + s->step / 2;
+	v = clamp(v, s->min, s->max);
+	offset = v - s->min;
+	offset = s->step * (offset / s->step);
+	s->val = s->min + offset;
+}
+
+int led_set_flash_timeout(struct led_classdev_flash *flash, u32 timeout)
+{
+	struct led_classdev *led_cdev = &flash->led_cdev;
+	struct led_flash_setting *s = &flash->timeout;
+	int ret = 0;
+
+	s->val = timeout;
+	led_clamp_align(s);
+
+	if (!(led_cdev->flags & LED_SUSPENDED))
+		ret = call_flash_op(flash, timeout_set, s->val);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(led_set_flash_timeout);
+
+int led_get_flash_fault(struct led_classdev_flash *flash, u32 *fault)
+{
+	return call_flash_op(flash, fault_get, fault);
+}
+EXPORT_SYMBOL_GPL(led_get_flash_fault);
+
+int led_set_flash_brightness(struct led_classdev_flash *flash,
+				u32 brightness)
+{
+	struct led_classdev *led_cdev = &flash->led_cdev;
+	struct led_flash_setting *s = &flash->brightness;
+	int ret = 0;
+
+	s->val = brightness;
+	led_clamp_align(s);
+
+	if (!(led_cdev->flags & LED_SUSPENDED))
+		ret = call_flash_op(flash, flash_brightness_set, s->val);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(led_set_flash_brightness);
+
+int led_update_flash_brightness(struct led_classdev_flash *flash)
+{
+	struct led_flash_setting *s = &flash->brightness;
+	u32 brightness;
+	int ret = 0;
+
+	if (has_flash_op(flash, flash_brightness_get)) {
+		ret = call_flash_op(flash, flash_brightness_get,
+						&brightness);
+		if (ret < 0)
+			return ret;
+		s->val = brightness;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(led_update_flash_brightness);
+
+int led_set_indicator_brightness(struct led_classdev_flash *flash,
+					u32 brightness)
+{
+	struct led_classdev *led_cdev = &flash->led_cdev;
+	struct led_flash_setting *s = flash->indicator_brightness;
+	int ret = 0;
+
+	if (!s)
+		return -EINVAL;
+
+	s->val = brightness;
+	led_clamp_align(s);
+
+	if (!(led_cdev->flags & LED_SUSPENDED))
+		ret = call_flash_op(flash, indicator_brightness_set, s->val);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(led_set_indicator_brightness);
+
+int led_update_indicator_brightness(struct led_classdev_flash *flash)
+{
+	struct led_flash_setting *s = flash->indicator_brightness;
+	u32 brightness;
+	int ret = 0;
+
+	if (!s)
+		return -EINVAL;
+
+	if (has_flash_op(flash, indicator_brightness_get)) {
+		ret = call_flash_op(flash, indicator_brightness_get,
+							&brightness);
+		if (ret < 0)
+			return ret;
+		s->val = brightness;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(led_update_indicator_brightness);
+
+MODULE_AUTHOR("Jacek Anaszewski <j.anaszewski@samsung.com>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("LED Flash Class Interface");
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 5a11a07..d398b87 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -183,6 +183,10 @@ EXPORT_SYMBOL_GPL(led_classdev_suspend);
 void led_classdev_resume(struct led_classdev *led_cdev)
 {
 	led_cdev->brightness_set(led_cdev, led_cdev->brightness);
+
+	if (led_cdev->flash_resume)
+		led_cdev->flash_resume(led_cdev);
+
 	led_cdev->flags &= ~LED_SUSPENDED;
 }
 EXPORT_SYMBOL_GPL(led_classdev_resume);
diff --git a/include/linux/led-class-flash.h b/include/linux/led-class-flash.h
new file mode 100644
index 0000000..fcc15ed
--- /dev/null
+++ b/include/linux/led-class-flash.h
@@ -0,0 +1,238 @@
+/*
+ * LED Flash Class interface
+ *
+ * Copyright (C) 2014 Samsung Electronics Co., Ltd.
+ * Author: Jacek Anaszewski <j.anaszewski@samsung.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+#ifndef __LINUX_FLASH_LEDS_H_INCLUDED
+#define __LINUX_FLASH_LEDS_H_INCLUDED
+
+#include <linux/leds.h>
+
+struct led_classdev_flash;
+struct device_node;
+
+/*
+ * Supported led fault bits - must be kept in synch
+ * with V4L2_FLASH_FAULT bits.
+ */
+#define LED_FAULT_OVER_VOLTAGE		 V4L2_FLASH_FAULT_OVER_VOLTAGE
+#define LED_FAULT_TIMEOUT		 V4L2_FLASH_FAULT_TIMEOUT
+#define LED_FAULT_OVER_TEMPERATURE	 V4L2_FLASH_FAULT_OVER_TEMPERATURE
+#define LED_FAULT_SHORT_CIRCUIT		 V4L2_FLASH_FAULT_SHORT_CIRCUIT
+#define LED_FAULT_OVER_CURRENT		 V4L2_FLASH_FAULT_OVER_CURRENT
+#define LED_FAULT_INDICATOR		 V4L2_FLASH_FAULT_INDICATOR
+#define LED_FAULT_UNDER_VOLTAGE		 V4L2_FLASH_FAULT_UNDER_VOLTAGE
+#define LED_FAULT_INPUT_VOLTAGE		 V4L2_FLASH_FAULT_INPUT_VOLTAGE
+#define LED_FAULT_LED_OVER_TEMPERATURE	 V4L2_FLASH_OVER_TEMPERATURE
+
+#define LED_FLASH_MAX_SYSFS_GROUPS 5
+
+struct led_flash_ops {
+	/* set flash brightness */
+	int (*flash_brightness_set)(struct led_classdev_flash *flash,
+					u32 brightness);
+	/* get flash brightness */
+	int (*flash_brightness_get)(struct led_classdev_flash *flash,
+					u32 *brightness);
+	/* set flash indicator brightness */
+	int (*indicator_brightness_set)(struct led_classdev_flash *flash,
+					u32 brightness);
+	/* get flash indicator brightness */
+	int (*indicator_brightness_get)(struct led_classdev_flash *flash,
+					u32 *brightness);
+	/* set flash strobe state */
+	int (*strobe_set)(struct led_classdev_flash *flash, bool state);
+	/* get flash strobe state */
+	int (*strobe_get)(struct led_classdev_flash *flash, bool *state);
+	/* set flash timeout */
+	int (*timeout_set)(struct led_classdev_flash *flash, u32 timeout);
+	/* get the flash LED fault */
+	int (*fault_get)(struct led_classdev_flash *flash, u32 *fault);
+};
+
+/*
+ * Current value of a flash setting along
+ * with its constraints.
+ */
+struct led_flash_setting {
+	/* maximum allowed value */
+	u32 min;
+	/* maximum allowed value */
+	u32 max;
+	/* step value */
+	u32 step;
+	/* current value */
+	u32 val;
+};
+
+/*
+ * Aggregated flash settings - designed for ease
+ * of passing initialization data to the clients
+ * wrapping a LED Flash class device.
+ */
+struct led_flash_config {
+	struct led_flash_setting torch_brightness;
+	struct led_flash_setting flash_brightness;
+	struct led_flash_setting indicator_brightness;
+	struct led_flash_setting flash_timeout;
+	u32 flash_faults;
+};
+
+struct led_classdev_flash {
+	/* led-flash-manager uses it to link flashes */
+	struct list_head list;
+	/* led class device */
+	struct led_classdev led_cdev;
+	/* flash led specific ops */
+	const struct led_flash_ops *ops;
+
+	/* flash sysfs groups */
+	struct attribute_group *sysfs_groups[LED_FLASH_MAX_SYSFS_GROUPS];
+
+	/* flash brightness value in microamperes along with its constraints */
+	struct led_flash_setting brightness;
+
+	/* timeout value in microseconds along with its constraints */
+	struct led_flash_setting timeout;
+
+	/*
+	 * Indicator brightness value in microamperes along with
+	 * its constraints - this is an optional setting and must
+	 * be allocated by the driver if the device supports privacy
+	 * indicator led.
+	 */
+	struct led_flash_setting *indicator_brightness;
+};
+
+static inline struct led_classdev_flash *lcdev_to_flash(
+						struct led_classdev *lcdev)
+{
+	return container_of(lcdev, struct led_classdev_flash, led_cdev);
+}
+
+/**
+ * led_classdev_flash_register - register a new object of led_classdev class
+				 with support for flash LEDs
+ * @parent: the flash LED to register
+ * @flash: the led_classdev_flash structure for this device
+ * @node: device tree node of the LED Flash Class device - it must be
+	  initialized if the device is to be registered in the flash manager
+ *
+ * Returns: 0 on success or negative error value on failure
+ */
+int led_classdev_flash_register(struct device *parent,
+				struct led_classdev_flash *flash,
+				struct device_node *node);
+
+/**
+ * led_classdev_flash_unregister - unregisters an object of led_classdev class
+				   with support for flash LEDs
+ * @flash: the flash LED to unregister
+ *
+ * Unregisters a previously registered via led_classdev_flash_register object
+ */
+void led_classdev_flash_unregister(struct led_classdev_flash *flash);
+
+/**
+ * led_set_flash_strobe - setup flash strobe
+ * @flash: the flash LED to set strobe on
+ * @state: 1 - strobe flash, 0 - stop flash strobe
+ *
+ * Setup flash strobe - trigger flash strobe
+ *
+ * Returns: 0 on success or negative error value on failure
+ */
+extern int led_set_flash_strobe(struct led_classdev_flash *flash,
+				bool state);
+
+/**
+ * led_get_flash_strobe - get flash strobe status
+ * @flash: the flash LED to query
+ * @state: 1 - flash is strobing, 0 - flash is off
+ *
+ * Check whether the flash is strobing at the moment or not.
+ *
+u* Returns: 0 on success or negative error value on failure
+ */
+extern int led_get_flash_strobe(struct led_classdev_flash *flash,
+				bool *state);
+/**
+ * led_set_flash_brightness - set flash LED brightness
+ * @flash: the flash LED to set
+ * @brightness: the brightness to set it to
+ *
+ * Returns: 0 on success or negative error value on failure
+ *
+ * Set a flash LED's brightness.
+ */
+extern int led_set_flash_brightness(struct led_classdev_flash *flash,
+					u32 brightness);
+
+/**
+ * led_update_flash_brightness - update flash LED brightness
+ * @flash: the flash LED to query
+ *
+ * Get a flash LED's current brightness and update led_flash->brightness
+ * member with the obtained value.
+ *
+ * Returns: 0 on success or negative error value on failure
+ */
+extern int led_update_flash_brightness(struct led_classdev_flash *flash);
+
+/**
+ * led_set_flash_timeout - set flash LED timeout
+ * @flash: the flash LED to set
+ * @timeout: the flash timeout to set it to
+ *
+ * Set the flash strobe duration. The duration set by the driver
+ * is returned in the timeout argument and may differ from the
+ * one that was originally passed.
+ *
+ * Returns: 0 on success or negative error value on failure
+ */
+extern int led_set_flash_timeout(struct led_classdev_flash *flash,
+					u32 timeout);
+
+/**
+ * led_get_flash_fault - get the flash LED fault
+ * @flash: the flash LED to query
+ * @fault: bitmask containing flash faults
+ *
+ * Get the flash LED fault.
+ *
+ * Returns: 0 on success or negative error value on failure
+ */
+extern int led_get_flash_fault(struct led_classdev_flash *flash,
+					u32 *fault);
+
+/**
+ * led_set_indicator_brightness - set indicator LED brightness
+ * @flash: the flash LED to set
+ * @brightness: the brightness to set it to
+ *
+ * Set an indicator LED's brightness.
+ *
+ * Returns: 0 on success or negative error value on failure
+ */
+extern int led_set_indicator_brightness(struct led_classdev_flash *flash,
+					u32 led_brightness);
+
+/**
+ * led_update_indicator_brightness - update flash indicator LED brightness
+ * @flash: the flash LED to query
+ *
+ * Get a flash indicator LED's current brightness and update
+ * led_flash->indicator_brightness member with the obtained value.
+ *
+ * Returns: 0 on success or negative error value on failure
+ */
+extern int led_update_indicator_brightness(struct led_classdev_flash *flash);
+
+
+#endif	/* __LINUX_FLASH_LEDS_H_INCLUDED */
diff --git a/include/linux/leds.h b/include/linux/leds.h
index bc2a570..70fa0ad 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -45,6 +45,8 @@ struct led_classdev {
 #define LED_BLINK_INVERT	(1 << 19)
 #define LED_SYSFS_DISABLE	(1 << 20)
 #define LED_DEV_CAP_TORCH	(1 << 21)
+#define LED_DEV_CAP_FLASH	(1 << 22)
+#define LED_DEV_CAP_INDICATOR	(1 << 23)
 
 	/* Set LED brightness level */
 	/* Must not sleep, use a workqueue if needed */
@@ -83,6 +85,7 @@ struct led_classdev {
 	unsigned long		 blink_delay_on, blink_delay_off;
 	struct timer_list	 blink_timer;
 	int			 blink_brightness;
+	void			(*flash_resume)(struct led_classdev *led_cdev);
 
 	struct work_struct	set_brightness_work;
 	int			delayed_set_value;
-- 
1.7.9.5

Re: [PATCH/RFC v6 3/3] leds: Add LED Flash Class wrapper to LED subsystem

[Bryan Wu]

On Mon, Sep 22, 2014 at 8:21 AM, Jacek Anaszewski
<j.anaszewski@samsung.com> wrote:
> Some LED devices support two operation modes - torch and flash.

I got several terms here:
flash, torch and indicator.

And we have 3 CAPs
CAP_TORCH
CAP_FLASH
CAP_INDICATOR

I assume flash == indicator but it doesn't from the code. So what's
the difference between flash and indicator.

> This patch provides support for flash LED devices in the LED subsystem
> by introducing new sysfs attributes and kernel internal interface.
> The attributes being introduced are: flash_brightness, flash_strobe,
> flash_timeout, max_flash_timeout, max_flash_brightness, flash_fault,
> indicator_brightness and  max_indicator_brightness. All the flash
> related features are placed in a separate module.
>

There is no torch interface? only flash and indicator.

> The modifications aim to be compatible with V4L2 framework requirements
> related to the flash devices management. The design assumes that V4L2
> sub-device can take of the LED class device control and communicate
> with it through the kernel internal interface. When V4L2 Flash sub-device
> file is opened, the LED class device sysfs interface is made
> unavailable.
>
> Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
> Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
> Cc: Bryan Wu <cooloney@gmail.com>
> Cc: Richard Purdie <rpurdie@rpsys.net>
> ---
>  drivers/leds/Kconfig            |   11 +
>  drivers/leds/Makefile           |    1 +
>  drivers/leds/led-class-flash.c  |  557 +++++++++++++++++++++++++++++++++++++++
>  drivers/leds/led-class.c        |    4 +
>  include/linux/led-class-flash.h |  238 +++++++++++++++++
>  include/linux/leds.h            |    3 +
>  6 files changed, 814 insertions(+)
>  create mode 100644 drivers/leds/led-class-flash.c
>  create mode 100644 include/linux/led-class-flash.h
>
> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> index 8c96e2d..3c58021 100644
> --- a/drivers/leds/Kconfig
> +++ b/drivers/leds/Kconfig
> @@ -22,6 +22,17 @@ config LEDS_CLASS
>           This option enables the led sysfs class in /sys/class/leds.  You'll
>           need this to do anything useful with LEDs.  If unsure, say N.
>
> +config LEDS_CLASS_FLASH
> +       tristate "LED Flash Class Support"
> +       depends on LEDS_CLASS
> +       depends on OF
> +       help
> +         This option enables the flash led sysfs class in /sys/class/leds.
> +         It wrapps LED Class and adds flash LEDs specific sysfs attributes
> +         and kernel internal API to it. You'll need this to provide support
> +         for the flash related features of a LED device. It can be built
> +         as a module.
> +
>  comment "LED drivers"
>
>  config LEDS_88PM860X
> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
> index d8cc5f2..9238b8a 100644
> --- a/drivers/leds/Makefile
> +++ b/drivers/leds/Makefile
> @@ -2,6 +2,7 @@
>  # LED Core
>  obj-$(CONFIG_NEW_LEDS)                 += led-core.o
>  obj-$(CONFIG_LEDS_CLASS)               += led-class.o
> +obj-$(CONFIG_LEDS_CLASS_FLASH)         += led-class-flash.o
>  obj-$(CONFIG_LEDS_TRIGGERS)            += led-triggers.o
>
>  # LED Platform Drivers
> diff --git a/drivers/leds/led-class-flash.c b/drivers/leds/led-class-flash.c
> new file mode 100644
> index 0000000..f1ba539
> --- /dev/null
> +++ b/drivers/leds/led-class-flash.c
> @@ -0,0 +1,557 @@
> +/*
> + * LED Flash Class interface
> + *
> + * Copyright (C) 2014 Samsung Electronics Co., Ltd.
> + * Author: Jacek Anaszewski <j.anaszewski@samsung.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/init.h>
> +#include <linux/leds.h>
> +#include <linux/led-class-flash.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include "leds.h"
> +
> +#define has_flash_op(flash, op)                                \
> +       (flash && flash->ops->op)
> +
> +#define call_flash_op(flash, op, args...)              \
> +       ((has_flash_op(flash, op)) ?                    \
> +                       (flash->ops->op(flash, args)) : \
> +                       -EINVAL)
> +
> +static ssize_t flash_brightness_store(struct device *dev,
> +               struct device_attribute *attr, const char *buf, size_t size)
> +{
> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +       unsigned long state;
> +       ssize_t ret;
> +
> +       mutex_lock(&led_cdev->led_access);
> +
> +       if (led_sysfs_is_disabled(led_cdev)) {
> +               ret = -EBUSY;
> +               goto unlock;
> +       }
> +
> +       ret = kstrtoul(buf, 10, &state);
> +       if (ret)
> +               goto unlock;
> +
> +       ret = led_set_flash_brightness(flash, state);
> +       if (ret < 0)
> +               goto unlock;
> +
> +       ret = size;
> +unlock:
> +       mutex_unlock(&led_cdev->led_access);
> +       return ret;
> +}
> +
> +static ssize_t flash_brightness_show(struct device *dev,
> +               struct device_attribute *attr, char *buf)
> +{
> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +
> +       /* no lock needed for this */
> +       led_update_flash_brightness(flash);
> +
> +       return sprintf(buf, "%u\n", flash->brightness.val);
> +}
> +static DEVICE_ATTR_RW(flash_brightness);
> +
> +static ssize_t max_flash_brightness_show(struct device *dev,
> +               struct device_attribute *attr, char *buf)
> +{
> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +
> +       return sprintf(buf, "%u\n", flash->brightness.max);
> +}
> +static DEVICE_ATTR_RO(max_flash_brightness);
> +
> +static ssize_t indicator_brightness_store(struct device *dev,
> +               struct device_attribute *attr, const char *buf, size_t size)
> +{
> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +       unsigned long state;
> +       ssize_t ret;
> +
> +       mutex_lock(&led_cdev->led_access);
> +
> +       if (led_sysfs_is_disabled(led_cdev)) {
> +               ret = -EBUSY;
> +               goto unlock;
> +       }
> +
> +       ret = kstrtoul(buf, 10, &state);
> +       if (ret)
> +               goto unlock;
> +
> +       ret = led_set_indicator_brightness(flash, state);
> +       if (ret < 0)
> +               goto unlock;
> +
> +       ret = size;
> +unlock:
> +       mutex_unlock(&led_cdev->led_access);
> +       return ret;
> +}
> +
> +static ssize_t indicator_brightness_show(struct device *dev,
> +               struct device_attribute *attr, char *buf)
> +{
> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +
> +       /* no lock needed for this */
> +       led_update_indicator_brightness(flash);
> +
> +       return sprintf(buf, "%u\n", flash->indicator_brightness->val);
> +}
> +static DEVICE_ATTR_RW(indicator_brightness);
> +
> +static ssize_t max_indicator_brightness_show(struct device *dev,
> +               struct device_attribute *attr, char *buf)
> +{
> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +
> +       return sprintf(buf, "%u\n", flash->indicator_brightness->max);
> +}
> +static DEVICE_ATTR_RO(max_indicator_brightness);
> +
> +static ssize_t flash_strobe_store(struct device *dev,
> +               struct device_attribute *attr, const char *buf, size_t size)
> +{
> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +       unsigned long state;
> +       ssize_t ret = -EINVAL;
> +
> +       mutex_lock(&led_cdev->led_access);
> +
> +       if (led_sysfs_is_disabled(led_cdev)) {
> +               ret = -EBUSY;
> +               goto unlock;
> +       }
> +
> +       ret = kstrtoul(buf, 10, &state);
> +       if (ret)
> +               goto unlock;
> +
> +       if (state < 0 || state > 1) {
> +               ret = -EINVAL;
> +               goto unlock;
> +       }
> +
> +       ret = led_set_flash_strobe(flash, state);
> +       if (ret < 0)
> +               goto unlock;
> +       ret = size;
> +unlock:
> +       mutex_unlock(&led_cdev->led_access);
> +       return ret;
> +}
> +
> +static ssize_t flash_strobe_show(struct device *dev,
> +               struct device_attribute *attr, char *buf)
> +{
> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +       bool state;
> +       int ret;
> +
> +       /* no lock needed for this */
> +       ret = led_get_flash_strobe(flash, &state);
> +       if (ret < 0)
> +               return ret;
> +
> +       return sprintf(buf, "%u\n", state);
> +}
> +static DEVICE_ATTR_RW(flash_strobe);
> +
> +static ssize_t flash_timeout_store(struct device *dev,
> +               struct device_attribute *attr, const char *buf, size_t size)
> +{
> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +       unsigned long flash_timeout;
> +       ssize_t ret;
> +
> +       mutex_lock(&led_cdev->led_access);
> +
> +       if (led_sysfs_is_disabled(led_cdev)) {
> +               ret = -EBUSY;
> +               goto unlock;
> +       }
> +
> +       ret = kstrtoul(buf, 10, &flash_timeout);
> +       if (ret)
> +               goto unlock;
> +
> +       ret = led_set_flash_timeout(flash, flash_timeout);
> +       if (ret < 0)
> +               goto unlock;
> +
> +       ret = size;
> +unlock:
> +       mutex_unlock(&led_cdev->led_access);
> +       return ret;
> +}
> +
> +static ssize_t flash_timeout_show(struct device *dev,
> +               struct device_attribute *attr, char *buf)
> +{
> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +
> +       return sprintf(buf, "%u\n", flash->timeout.val);
> +}
> +static DEVICE_ATTR_RW(flash_timeout);
> +
> +static ssize_t max_flash_timeout_show(struct device *dev,
> +               struct device_attribute *attr, char *buf)
> +{
> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +
> +       return sprintf(buf, "%u\n", flash->timeout.max);
> +}
> +static DEVICE_ATTR_RO(max_flash_timeout);
> +
> +static ssize_t flash_fault_show(struct device *dev,
> +               struct device_attribute *attr, char *buf)
> +{
> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +       u32 fault;
> +       int ret;
> +
> +       ret = led_get_flash_fault(flash, &fault);
> +       if (ret < 0)
> +               return -EINVAL;
> +
> +       return sprintf(buf, "0x%8.8x\n", fault);
> +}
> +static DEVICE_ATTR_RO(flash_fault);
> +
> +static struct attribute *led_flash_strobe_attrs[] = {
> +       &dev_attr_flash_strobe.attr,
> +       NULL,
> +};
> +
> +static struct attribute *led_flash_indicator_attrs[] = {
> +       &dev_attr_indicator_brightness.attr,
> +       &dev_attr_max_indicator_brightness.attr,
> +       NULL,
> +};
> +
> +static struct attribute *led_flash_timeout_attrs[] = {
> +       &dev_attr_flash_timeout.attr,
> +       &dev_attr_max_flash_timeout.attr,
> +       NULL,
> +};
> +
> +static struct attribute *led_flash_brightness_attrs[] = {
> +       &dev_attr_flash_brightness.attr,
> +       &dev_attr_max_flash_brightness.attr,
> +       NULL,
> +};
> +
> +static struct attribute *led_flash_fault_attrs[] = {
> +       &dev_attr_flash_fault.attr,
> +       NULL,
> +};
> +
> +static struct attribute_group led_flash_strobe_group = {
> +       .attrs = led_flash_strobe_attrs,
> +};
> +
> +static struct attribute_group led_flash_brightness_group = {
> +       .attrs = led_flash_brightness_attrs,
> +};
> +
> +static struct attribute_group led_flash_timeout_group = {
> +       .attrs = led_flash_timeout_attrs,
> +};
> +
> +static struct attribute_group led_flash_indicator_group = {
> +       .attrs = led_flash_indicator_attrs,
> +};
> +
> +static struct attribute_group led_flash_fault_group = {
> +       .attrs = led_flash_fault_attrs,
> +};
> +
> +static void led_flash_resume(struct led_classdev *led_cdev)
> +{
> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +
> +       call_flash_op(flash, flash_brightness_set, flash->brightness.val);
> +       call_flash_op(flash, timeout_set, flash->timeout.val);
> +       call_flash_op(flash, indicator_brightness_set,
> +                               flash->indicator_brightness->val);
> +}
> +
> +static void led_flash_remove_sysfs_groups(struct led_classdev_flash *flash)
> +{
> +       struct led_classdev *led_cdev = &flash->led_cdev;
> +       int i;
> +
> +       for (i = 0; i < LED_FLASH_MAX_SYSFS_GROUPS; ++i)
> +               if (flash->sysfs_groups[i])
> +                       sysfs_remove_group(&led_cdev->dev->kobj,
> +                                               flash->sysfs_groups[i]);
> +}
> +
> +static int led_flash_create_sysfs_groups(struct led_classdev_flash *flash)
> +{
> +       struct led_classdev *led_cdev = &flash->led_cdev;
> +       const struct led_flash_ops *ops = flash->ops;
> +       int ret, num_sysfs_groups = 0;
> +
> +       memset(flash->sysfs_groups, 0, sizeof(*flash->sysfs_groups) *
> +                                               LED_FLASH_MAX_SYSFS_GROUPS);
> +
> +       ret = sysfs_create_group(&led_cdev->dev->kobj, &led_flash_strobe_group);
> +       if (ret < 0)
> +               goto err_create_group;
> +       flash->sysfs_groups[num_sysfs_groups++] = &led_flash_strobe_group;
> +
> +       if (flash->indicator_brightness) {
> +               ret = sysfs_create_group(&led_cdev->dev->kobj,
> +                                       &led_flash_indicator_group);
> +               if (ret < 0)
> +                       goto err_create_group;
> +               flash->sysfs_groups[num_sysfs_groups++] =
> +                                       &led_flash_indicator_group;
> +       }
> +
> +       if (ops->flash_brightness_set) {
> +               ret = sysfs_create_group(&led_cdev->dev->kobj,
> +                                       &led_flash_brightness_group);
> +               if (ret < 0)
> +                       goto err_create_group;
> +               flash->sysfs_groups[num_sysfs_groups++] =
> +                                       &led_flash_brightness_group;
> +       }
> +
> +       if (ops->timeout_set) {
> +               ret = sysfs_create_group(&led_cdev->dev->kobj,
> +                                       &led_flash_timeout_group);
> +               if (ret < 0)
> +                       goto err_create_group;
> +               flash->sysfs_groups[num_sysfs_groups++] =
> +                                       &led_flash_timeout_group;
> +       }
> +
> +       if (ops->fault_get) {
> +               ret = sysfs_create_group(&led_cdev->dev->kobj,
> +                                       &led_flash_fault_group);
> +               if (ret < 0)
> +                       goto err_create_group;
> +               flash->sysfs_groups[num_sysfs_groups++] =
> +                                       &led_flash_fault_group;
> +       }
> +
> +       return 0;
> +
> +err_create_group:
> +       led_flash_remove_sysfs_groups(flash);
> +       return ret;
> +}
> +
> +int led_classdev_flash_register(struct device *parent,
> +                               struct led_classdev_flash *flash,
> +                               struct device_node *node)
> +{
> +       struct led_classdev *led_cdev;
> +       const struct led_flash_ops *ops;
> +       int ret = -EINVAL;
> +
> +       if (!flash)
> +               return -EINVAL;
> +
> +       led_cdev = &flash->led_cdev;
> +
> +       /* Torch capability is default for every LED Flash Class device */
> +       led_cdev->flags |= LED_DEV_CAP_TORCH;
> +
> +       if (led_cdev->flags & LED_DEV_CAP_FLASH) {
> +               if (!led_cdev->torch_brightness_set)
> +                       return -EINVAL;
> +
> +               ops = flash->ops;
> +               if (!ops || !ops->strobe_set)
> +                       return -EINVAL;
> +
> +               if ((led_cdev->flags & LED_DEV_CAP_INDICATOR) &&
> +                   (!flash->indicator_brightness ||
> +                    !ops->indicator_brightness_set))
> +                       return -EINVAL;
> +
> +               led_cdev->flash_resume = led_flash_resume;
> +       }
> +
> +       /* Register led class device */
> +       ret = led_classdev_register(parent, led_cdev);
> +       if (ret < 0)
> +               return -EINVAL;
> +
> +       /* Create flash led specific sysfs attributes */
> +       ret = led_flash_create_sysfs_groups(flash);
> +       if (ret < 0)
> +               goto err_create_sysfs_groups;
> +

Here might cause some race condition. Please check the commits
commit d0d480cce8f522b37c2c1de38230fc9ad15fa506
Author: Johan Hovold <johan@kernel.org>
Date:   Wed Jun 25 10:08:44 2014 -0700

    leds: add led-class attribute-group support

    Allow led-class devices to be created with optional attribute groups.

    This is needed in order to allow led drivers to create custom device
    attributes in a race-free manner.

    Signed-off-by: Johan Hovold <johan@kernel.org>
    Signed-off-by: Bryan Wu <cooloney@gmail.com>

And related fixes in drivers/leds/ recently.

> +       return 0;
> +
> +err_create_sysfs_groups:
> +       led_classdev_unregister(led_cdev);
> +
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(led_classdev_flash_register);
> +
> +void led_classdev_flash_unregister(struct led_classdev_flash *flash)
> +{
> +       if (!flash)
> +               return;
> +
> +       led_flash_remove_sysfs_groups(flash);
> +       led_classdev_unregister(&flash->led_cdev);
> +}
> +EXPORT_SYMBOL_GPL(led_classdev_flash_unregister);
> +
> +int led_set_flash_strobe(struct led_classdev_flash *flash, bool state)
> +{
> +       return call_flash_op(flash, strobe_set, state);
> +}
> +EXPORT_SYMBOL_GPL(led_set_flash_strobe);
> +
> +int led_get_flash_strobe(struct led_classdev_flash *flash, bool *state)
> +{
> +       return call_flash_op(flash, strobe_get, state);
> +}
> +EXPORT_SYMBOL_GPL(led_get_flash_strobe);
> +
> +static void led_clamp_align(struct led_flash_setting *s)
> +{
> +       u32 v, offset;
> +
> +       v = s->val + s->step / 2;
> +       v = clamp(v, s->min, s->max);
> +       offset = v - s->min;
> +       offset = s->step * (offset / s->step);
> +       s->val = s->min + offset;
> +}
> +
> +int led_set_flash_timeout(struct led_classdev_flash *flash, u32 timeout)
> +{
> +       struct led_classdev *led_cdev = &flash->led_cdev;
> +       struct led_flash_setting *s = &flash->timeout;
> +       int ret = 0;
> +
> +       s->val = timeout;
> +       led_clamp_align(s);
> +
> +       if (!(led_cdev->flags & LED_SUSPENDED))
> +               ret = call_flash_op(flash, timeout_set, s->val);
> +
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(led_set_flash_timeout);
> +
> +int led_get_flash_fault(struct led_classdev_flash *flash, u32 *fault)
> +{
> +       return call_flash_op(flash, fault_get, fault);
> +}
> +EXPORT_SYMBOL_GPL(led_get_flash_fault);
> +
> +int led_set_flash_brightness(struct led_classdev_flash *flash,
> +                               u32 brightness)
> +{
> +       struct led_classdev *led_cdev = &flash->led_cdev;
> +       struct led_flash_setting *s = &flash->brightness;
> +       int ret = 0;
> +
> +       s->val = brightness;
> +       led_clamp_align(s);
> +
> +       if (!(led_cdev->flags & LED_SUSPENDED))
> +               ret = call_flash_op(flash, flash_brightness_set, s->val);
> +
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(led_set_flash_brightness);
> +
> +int led_update_flash_brightness(struct led_classdev_flash *flash)
> +{
> +       struct led_flash_setting *s = &flash->brightness;
> +       u32 brightness;
> +       int ret = 0;
> +
> +       if (has_flash_op(flash, flash_brightness_get)) {
I think call_flash_op() will call has_flash_op() in your previous definitions.

> +               ret = call_flash_op(flash, flash_brightness_get,
> +                                               &brightness);


> +               if (ret < 0)
> +                       return ret;
> +               s->val = brightness;
> +       }
> +
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(led_update_flash_brightness);
> +
> +int led_set_indicator_brightness(struct led_classdev_flash *flash,
> +                                       u32 brightness)
> +{
> +       struct led_classdev *led_cdev = &flash->led_cdev;
> +       struct led_flash_setting *s = flash->indicator_brightness;
> +       int ret = 0;
> +
> +       if (!s)
> +               return -EINVAL;
> +
> +       s->val = brightness;
> +       led_clamp_align(s);
> +
> +       if (!(led_cdev->flags & LED_SUSPENDED))
> +               ret = call_flash_op(flash, indicator_brightness_set, s->val);
> +
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(led_set_indicator_brightness);
> +
> +int led_update_indicator_brightness(struct led_classdev_flash *flash)
> +{
> +       struct led_flash_setting *s = flash->indicator_brightness;
> +       u32 brightness;
> +       int ret = 0;
> +
> +       if (!s)
> +               return -EINVAL;
> +
> +       if (has_flash_op(flash, indicator_brightness_get)) {
> +               ret = call_flash_op(flash, indicator_brightness_get,
> +                                                       &brightness);
> +               if (ret < 0)
> +                       return ret;
> +               s->val = brightness;
> +       }
> +
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(led_update_indicator_brightness);
> +
> +MODULE_AUTHOR("Jacek Anaszewski <j.anaszewski@samsung.com>");
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("LED Flash Class Interface");
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index 5a11a07..d398b87 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -183,6 +183,10 @@ EXPORT_SYMBOL_GPL(led_classdev_suspend);
>  void led_classdev_resume(struct led_classdev *led_cdev)
>  {
>         led_cdev->brightness_set(led_cdev, led_cdev->brightness);
> +
> +       if (led_cdev->flash_resume)
> +               led_cdev->flash_resume(led_cdev);
> +
>         led_cdev->flags &= ~LED_SUSPENDED;
>  }
>  EXPORT_SYMBOL_GPL(led_classdev_resume);
> diff --git a/include/linux/led-class-flash.h b/include/linux/led-class-flash.h
> new file mode 100644
> index 0000000..fcc15ed
> --- /dev/null
> +++ b/include/linux/led-class-flash.h
> @@ -0,0 +1,238 @@
> +/*
> + * LED Flash Class interface
> + *
> + * Copyright (C) 2014 Samsung Electronics Co., Ltd.
> + * Author: Jacek Anaszewski <j.anaszewski@samsung.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + */
> +#ifndef __LINUX_FLASH_LEDS_H_INCLUDED
> +#define __LINUX_FLASH_LEDS_H_INCLUDED
> +
> +#include <linux/leds.h>
> +
> +struct led_classdev_flash;
> +struct device_node;
> +
> +/*
> + * Supported led fault bits - must be kept in synch
> + * with V4L2_FLASH_FAULT bits.
> + */
> +#define LED_FAULT_OVER_VOLTAGE          V4L2_FLASH_FAULT_OVER_VOLTAGE
> +#define LED_FAULT_TIMEOUT               V4L2_FLASH_FAULT_TIMEOUT
> +#define LED_FAULT_OVER_TEMPERATURE      V4L2_FLASH_FAULT_OVER_TEMPERATURE
> +#define LED_FAULT_SHORT_CIRCUIT                 V4L2_FLASH_FAULT_SHORT_CIRCUIT
> +#define LED_FAULT_OVER_CURRENT          V4L2_FLASH_FAULT_OVER_CURRENT
> +#define LED_FAULT_INDICATOR             V4L2_FLASH_FAULT_INDICATOR
> +#define LED_FAULT_UNDER_VOLTAGE                 V4L2_FLASH_FAULT_UNDER_VOLTAGE
> +#define LED_FAULT_INPUT_VOLTAGE                 V4L2_FLASH_FAULT_INPUT_VOLTAGE
> +#define LED_FAULT_LED_OVER_TEMPERATURE  V4L2_FLASH_OVER_TEMPERATURE
> +
> +#define LED_FLASH_MAX_SYSFS_GROUPS 5
> +
> +struct led_flash_ops {
> +       /* set flash brightness */
> +       int (*flash_brightness_set)(struct led_classdev_flash *flash,
> +                                       u32 brightness);
> +       /* get flash brightness */
> +       int (*flash_brightness_get)(struct led_classdev_flash *flash,
> +                                       u32 *brightness);
> +       /* set flash indicator brightness */
> +       int (*indicator_brightness_set)(struct led_classdev_flash *flash,
> +                                       u32 brightness);
> +       /* get flash indicator brightness */
> +       int (*indicator_brightness_get)(struct led_classdev_flash *flash,
> +                                       u32 *brightness);
> +       /* set flash strobe state */
> +       int (*strobe_set)(struct led_classdev_flash *flash, bool state);
> +       /* get flash strobe state */
> +       int (*strobe_get)(struct led_classdev_flash *flash, bool *state);
> +       /* set flash timeout */
> +       int (*timeout_set)(struct led_classdev_flash *flash, u32 timeout);
> +       /* get the flash LED fault */
> +       int (*fault_get)(struct led_classdev_flash *flash, u32 *fault);
> +};
> +
> +/*
> + * Current value of a flash setting along
> + * with its constraints.
> + */
> +struct led_flash_setting {
> +       /* maximum allowed value */
> +       u32 min;
> +       /* maximum allowed value */
> +       u32 max;
> +       /* step value */
> +       u32 step;
> +       /* current value */
> +       u32 val;
> +};
> +
> +/*
> + * Aggregated flash settings - designed for ease
> + * of passing initialization data to the clients
> + * wrapping a LED Flash class device.
> + */
> +struct led_flash_config {
> +       struct led_flash_setting torch_brightness;
> +       struct led_flash_setting flash_brightness;
> +       struct led_flash_setting indicator_brightness;
> +       struct led_flash_setting flash_timeout;
> +       u32 flash_faults;
> +};
> +
> +struct led_classdev_flash {
> +       /* led-flash-manager uses it to link flashes */
I guess no more led-flash-manager, right?
> +       struct list_head list;
> +       /* led class device */
> +       struct led_classdev led_cdev;
> +       /* flash led specific ops */
> +       const struct led_flash_ops *ops;
> +
> +       /* flash sysfs groups */
> +       struct attribute_group *sysfs_groups[LED_FLASH_MAX_SYSFS_GROUPS];
> +
> +       /* flash brightness value in microamperes along with its constraints */
> +       struct led_flash_setting brightness;
> +
> +       /* timeout value in microseconds along with its constraints */
> +       struct led_flash_setting timeout;
> +
> +       /*
> +        * Indicator brightness value in microamperes along with
> +        * its constraints - this is an optional setting and must
> +        * be allocated by the driver if the device supports privacy
> +        * indicator led.
> +        */
> +       struct led_flash_setting *indicator_brightness;
> +};
> +
> +static inline struct led_classdev_flash *lcdev_to_flash(
> +                                               struct led_classdev *lcdev)
> +{
> +       return container_of(lcdev, struct led_classdev_flash, led_cdev);
> +}
> +
> +/**
> + * led_classdev_flash_register - register a new object of led_classdev class
> +                                with support for flash LEDs
> + * @parent: the flash LED to register
> + * @flash: the led_classdev_flash structure for this device
> + * @node: device tree node of the LED Flash Class device - it must be
> +         initialized if the device is to be registered in the flash manager
> + *
> + * Returns: 0 on success or negative error value on failure
> + */
> +int led_classdev_flash_register(struct device *parent,
> +                               struct led_classdev_flash *flash,
> +                               struct device_node *node);
> +
> +/**
> + * led_classdev_flash_unregister - unregisters an object of led_classdev class
> +                                  with support for flash LEDs
> + * @flash: the flash LED to unregister
> + *
> + * Unregisters a previously registered via led_classdev_flash_register object
> + */
> +void led_classdev_flash_unregister(struct led_classdev_flash *flash);
> +
> +/**
> + * led_set_flash_strobe - setup flash strobe
> + * @flash: the flash LED to set strobe on
> + * @state: 1 - strobe flash, 0 - stop flash strobe
> + *
> + * Setup flash strobe - trigger flash strobe
> + *
> + * Returns: 0 on success or negative error value on failure
> + */
> +extern int led_set_flash_strobe(struct led_classdev_flash *flash,
> +                               bool state);
> +
> +/**
> + * led_get_flash_strobe - get flash strobe status
> + * @flash: the flash LED to query
> + * @state: 1 - flash is strobing, 0 - flash is off
> + *
> + * Check whether the flash is strobing at the moment or not.
> + *
> +u* Returns: 0 on success or negative error value on failure
> + */
> +extern int led_get_flash_strobe(struct led_classdev_flash *flash,
> +                               bool *state);
> +/**
> + * led_set_flash_brightness - set flash LED brightness
> + * @flash: the flash LED to set
> + * @brightness: the brightness to set it to
> + *
> + * Returns: 0 on success or negative error value on failure
> + *
> + * Set a flash LED's brightness.
> + */
> +extern int led_set_flash_brightness(struct led_classdev_flash *flash,
> +                                       u32 brightness);
> +
> +/**
> + * led_update_flash_brightness - update flash LED brightness
> + * @flash: the flash LED to query
> + *
> + * Get a flash LED's current brightness and update led_flash->brightness
> + * member with the obtained value.
> + *
> + * Returns: 0 on success or negative error value on failure
> + */
> +extern int led_update_flash_brightness(struct led_classdev_flash *flash);
> +
> +/**
> + * led_set_flash_timeout - set flash LED timeout
> + * @flash: the flash LED to set
> + * @timeout: the flash timeout to set it to
> + *
> + * Set the flash strobe duration. The duration set by the driver
> + * is returned in the timeout argument and may differ from the
> + * one that was originally passed.
> + *
> + * Returns: 0 on success or negative error value on failure
> + */
> +extern int led_set_flash_timeout(struct led_classdev_flash *flash,
> +                                       u32 timeout);
> +
> +/**
> + * led_get_flash_fault - get the flash LED fault
> + * @flash: the flash LED to query
> + * @fault: bitmask containing flash faults
> + *
> + * Get the flash LED fault.
> + *
> + * Returns: 0 on success or negative error value on failure
> + */
> +extern int led_get_flash_fault(struct led_classdev_flash *flash,
> +                                       u32 *fault);
> +
> +/**
> + * led_set_indicator_brightness - set indicator LED brightness
> + * @flash: the flash LED to set
> + * @brightness: the brightness to set it to
> + *
> + * Set an indicator LED's brightness.
> + *
> + * Returns: 0 on success or negative error value on failure
> + */
> +extern int led_set_indicator_brightness(struct led_classdev_flash *flash,
> +                                       u32 led_brightness);
> +
> +/**
> + * led_update_indicator_brightness - update flash indicator LED brightness
> + * @flash: the flash LED to query
> + *
> + * Get a flash indicator LED's current brightness and update
> + * led_flash->indicator_brightness member with the obtained value.
> + *
> + * Returns: 0 on success or negative error value on failure
> + */
> +extern int led_update_indicator_brightness(struct led_classdev_flash *flash);
> +
> +
> +#endif /* __LINUX_FLASH_LEDS_H_INCLUDED */
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index bc2a570..70fa0ad 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -45,6 +45,8 @@ struct led_classdev {
>  #define LED_BLINK_INVERT       (1 << 19)
>  #define LED_SYSFS_DISABLE      (1 << 20)
>  #define LED_DEV_CAP_TORCH      (1 << 21)
> +#define LED_DEV_CAP_FLASH      (1 << 22)
> +#define LED_DEV_CAP_INDICATOR  (1 << 23)
>
>         /* Set LED brightness level */
>         /* Must not sleep, use a workqueue if needed */
> @@ -83,6 +85,7 @@ struct led_classdev {
>         unsigned long            blink_delay_on, blink_delay_off;
>         struct timer_list        blink_timer;
>         int                      blink_brightness;
> +       void                    (*flash_resume)(struct led_classdev *led_cdev);
>
>         struct work_struct      set_brightness_work;
>         int                     delayed_set_value;
> --
> 1.7.9.5
>

Re: [PATCH/RFC v6 3/3] leds: Add LED Flash Class wrapper to LED subsystem

[Jacek Anaszewski]

Hi Bryan,

Thanks for a review.

On 11/04/2014 02:34 AM, Bryan Wu wrote:
> On Mon, Sep 22, 2014 at 8:21 AM, Jacek Anaszewski
> <j.anaszewski@samsung.com> wrote:
>> Some LED devices support two operation modes - torch and flash.
>
> I got several terms here:
> flash, torch and indicator.
>
> And we have 3 CAPs
> CAP_TORCH
> CAP_FLASH
> CAP_INDICATOR
>
> I assume flash == indicator but it doesn't from the code. So what's
> the difference between flash and indicator.

Indicator is a so-called "privacy led", that can be used to indicate
when a person is being photographed or filmed. V4L2 API defines
only an API for setting its intensity.

Adding Sakari.

>> This patch provides support for flash LED devices in the LED subsystem
>> by introducing new sysfs attributes and kernel internal interface.
>> The attributes being introduced are: flash_brightness, flash_strobe,
>> flash_timeout, max_flash_timeout, max_flash_brightness, flash_fault,
>> indicator_brightness and  max_indicator_brightness. All the flash
>> related features are placed in a separate module.
>>
>
> There is no torch interface? only flash and indicator.

LED Class interface is used for torch.

>> The modifications aim to be compatible with V4L2 framework requirements
>> related to the flash devices management. The design assumes that V4L2
>> sub-device can take of the LED class device control and communicate
>> with it through the kernel internal interface. When V4L2 Flash sub-device
>> file is opened, the LED class device sysfs interface is made
>> unavailable.
>>
>> Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
>> Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
>> Cc: Bryan Wu <cooloney@gmail.com>
>> Cc: Richard Purdie <rpurdie@rpsys.net>
>> ---
>>   drivers/leds/Kconfig            |   11 +
>>   drivers/leds/Makefile           |    1 +
>>   drivers/leds/led-class-flash.c  |  557 +++++++++++++++++++++++++++++++++++++++
>>   drivers/leds/led-class.c        |    4 +
>>   include/linux/led-class-flash.h |  238 +++++++++++++++++
>>   include/linux/leds.h            |    3 +
>>   6 files changed, 814 insertions(+)
>>   create mode 100644 drivers/leds/led-class-flash.c
>>   create mode 100644 include/linux/led-class-flash.h
>>
>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>> index 8c96e2d..3c58021 100644
>> --- a/drivers/leds/Kconfig
>> +++ b/drivers/leds/Kconfig
>> @@ -22,6 +22,17 @@ config LEDS_CLASS
>>            This option enables the led sysfs class in /sys/class/leds.  You'll
>>            need this to do anything useful with LEDs.  If unsure, say N.
>>
>> +config LEDS_CLASS_FLASH
>> +       tristate "LED Flash Class Support"
>> +       depends on LEDS_CLASS
>> +       depends on OF
>> +       help
>> +         This option enables the flash led sysfs class in /sys/class/leds.
>> +         It wrapps LED Class and adds flash LEDs specific sysfs attributes
>> +         and kernel internal API to it. You'll need this to provide support
>> +         for the flash related features of a LED device. It can be built
>> +         as a module.
>> +
>>   comment "LED drivers"
>>
>>   config LEDS_88PM860X
>> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
>> index d8cc5f2..9238b8a 100644
>> --- a/drivers/leds/Makefile
>> +++ b/drivers/leds/Makefile
>> @@ -2,6 +2,7 @@
>>   # LED Core
>>   obj-$(CONFIG_NEW_LEDS)                 += led-core.o
>>   obj-$(CONFIG_LEDS_CLASS)               += led-class.o
>> +obj-$(CONFIG_LEDS_CLASS_FLASH)         += led-class-flash.o
>>   obj-$(CONFIG_LEDS_TRIGGERS)            += led-triggers.o
>>
>>   # LED Platform Drivers
>> diff --git a/drivers/leds/led-class-flash.c b/drivers/leds/led-class-flash.c
>> new file mode 100644
>> index 0000000..f1ba539
>> --- /dev/null
>> +++ b/drivers/leds/led-class-flash.c
>> @@ -0,0 +1,557 @@
>> +/*
>> + * LED Flash Class interface
>> + *
>> + * Copyright (C) 2014 Samsung Electronics Co., Ltd.
>> + * Author: Jacek Anaszewski <j.anaszewski@samsung.com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + */
>> +
>> +#include <linux/device.h>
>> +#include <linux/init.h>
>> +#include <linux/leds.h>
>> +#include <linux/led-class-flash.h>
>> +#include <linux/module.h>
>> +#include <linux/slab.h>
>> +#include "leds.h"
>> +
>> +#define has_flash_op(flash, op)                                \
>> +       (flash && flash->ops->op)
>> +
>> +#define call_flash_op(flash, op, args...)              \
>> +       ((has_flash_op(flash, op)) ?                    \
>> +                       (flash->ops->op(flash, args)) : \
>> +                       -EINVAL)
>> +
>> +static ssize_t flash_brightness_store(struct device *dev,
>> +               struct device_attribute *attr, const char *buf, size_t size)
>> +{
>> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +       unsigned long state;
>> +       ssize_t ret;
>> +
>> +       mutex_lock(&led_cdev->led_access);
>> +
>> +       if (led_sysfs_is_disabled(led_cdev)) {
>> +               ret = -EBUSY;
>> +               goto unlock;
>> +       }
>> +
>> +       ret = kstrtoul(buf, 10, &state);
>> +       if (ret)
>> +               goto unlock;
>> +
>> +       ret = led_set_flash_brightness(flash, state);
>> +       if (ret < 0)
>> +               goto unlock;
>> +
>> +       ret = size;
>> +unlock:
>> +       mutex_unlock(&led_cdev->led_access);
>> +       return ret;
>> +}
>> +
>> +static ssize_t flash_brightness_show(struct device *dev,
>> +               struct device_attribute *attr, char *buf)
>> +{
>> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +
>> +       /* no lock needed for this */
>> +       led_update_flash_brightness(flash);
>> +
>> +       return sprintf(buf, "%u\n", flash->brightness.val);
>> +}
>> +static DEVICE_ATTR_RW(flash_brightness);
>> +
>> +static ssize_t max_flash_brightness_show(struct device *dev,
>> +               struct device_attribute *attr, char *buf)
>> +{
>> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +
>> +       return sprintf(buf, "%u\n", flash->brightness.max);
>> +}
>> +static DEVICE_ATTR_RO(max_flash_brightness);
>> +
>> +static ssize_t indicator_brightness_store(struct device *dev,
>> +               struct device_attribute *attr, const char *buf, size_t size)
>> +{
>> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +       unsigned long state;
>> +       ssize_t ret;
>> +
>> +       mutex_lock(&led_cdev->led_access);
>> +
>> +       if (led_sysfs_is_disabled(led_cdev)) {
>> +               ret = -EBUSY;
>> +               goto unlock;
>> +       }
>> +
>> +       ret = kstrtoul(buf, 10, &state);
>> +       if (ret)
>> +               goto unlock;
>> +
>> +       ret = led_set_indicator_brightness(flash, state);
>> +       if (ret < 0)
>> +               goto unlock;
>> +
>> +       ret = size;
>> +unlock:
>> +       mutex_unlock(&led_cdev->led_access);
>> +       return ret;
>> +}
>> +
>> +static ssize_t indicator_brightness_show(struct device *dev,
>> +               struct device_attribute *attr, char *buf)
>> +{
>> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +
>> +       /* no lock needed for this */
>> +       led_update_indicator_brightness(flash);
>> +
>> +       return sprintf(buf, "%u\n", flash->indicator_brightness->val);
>> +}
>> +static DEVICE_ATTR_RW(indicator_brightness);
>> +
>> +static ssize_t max_indicator_brightness_show(struct device *dev,
>> +               struct device_attribute *attr, char *buf)
>> +{
>> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +
>> +       return sprintf(buf, "%u\n", flash->indicator_brightness->max);
>> +}
>> +static DEVICE_ATTR_RO(max_indicator_brightness);
>> +
>> +static ssize_t flash_strobe_store(struct device *dev,
>> +               struct device_attribute *attr, const char *buf, size_t size)
>> +{
>> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +       unsigned long state;
>> +       ssize_t ret = -EINVAL;
>> +
>> +       mutex_lock(&led_cdev->led_access);
>> +
>> +       if (led_sysfs_is_disabled(led_cdev)) {
>> +               ret = -EBUSY;
>> +               goto unlock;
>> +       }
>> +
>> +       ret = kstrtoul(buf, 10, &state);
>> +       if (ret)
>> +               goto unlock;
>> +
>> +       if (state < 0 || state > 1) {
>> +               ret = -EINVAL;
>> +               goto unlock;
>> +       }
>> +
>> +       ret = led_set_flash_strobe(flash, state);
>> +       if (ret < 0)
>> +               goto unlock;
>> +       ret = size;
>> +unlock:
>> +       mutex_unlock(&led_cdev->led_access);
>> +       return ret;
>> +}
>> +
>> +static ssize_t flash_strobe_show(struct device *dev,
>> +               struct device_attribute *attr, char *buf)
>> +{
>> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +       bool state;
>> +       int ret;
>> +
>> +       /* no lock needed for this */
>> +       ret = led_get_flash_strobe(flash, &state);
>> +       if (ret < 0)
>> +               return ret;
>> +
>> +       return sprintf(buf, "%u\n", state);
>> +}
>> +static DEVICE_ATTR_RW(flash_strobe);
>> +
>> +static ssize_t flash_timeout_store(struct device *dev,
>> +               struct device_attribute *attr, const char *buf, size_t size)
>> +{
>> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +       unsigned long flash_timeout;
>> +       ssize_t ret;
>> +
>> +       mutex_lock(&led_cdev->led_access);
>> +
>> +       if (led_sysfs_is_disabled(led_cdev)) {
>> +               ret = -EBUSY;
>> +               goto unlock;
>> +       }
>> +
>> +       ret = kstrtoul(buf, 10, &flash_timeout);
>> +       if (ret)
>> +               goto unlock;
>> +
>> +       ret = led_set_flash_timeout(flash, flash_timeout);
>> +       if (ret < 0)
>> +               goto unlock;
>> +
>> +       ret = size;
>> +unlock:
>> +       mutex_unlock(&led_cdev->led_access);
>> +       return ret;
>> +}
>> +
>> +static ssize_t flash_timeout_show(struct device *dev,
>> +               struct device_attribute *attr, char *buf)
>> +{
>> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +
>> +       return sprintf(buf, "%u\n", flash->timeout.val);
>> +}
>> +static DEVICE_ATTR_RW(flash_timeout);
>> +
>> +static ssize_t max_flash_timeout_show(struct device *dev,
>> +               struct device_attribute *attr, char *buf)
>> +{
>> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +
>> +       return sprintf(buf, "%u\n", flash->timeout.max);
>> +}
>> +static DEVICE_ATTR_RO(max_flash_timeout);
>> +
>> +static ssize_t flash_fault_show(struct device *dev,
>> +               struct device_attribute *attr, char *buf)
>> +{
>> +       struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +       u32 fault;
>> +       int ret;
>> +
>> +       ret = led_get_flash_fault(flash, &fault);
>> +       if (ret < 0)
>> +               return -EINVAL;
>> +
>> +       return sprintf(buf, "0x%8.8x\n", fault);
>> +}
>> +static DEVICE_ATTR_RO(flash_fault);
>> +
>> +static struct attribute *led_flash_strobe_attrs[] = {
>> +       &dev_attr_flash_strobe.attr,
>> +       NULL,
>> +};
>> +
>> +static struct attribute *led_flash_indicator_attrs[] = {
>> +       &dev_attr_indicator_brightness.attr,
>> +       &dev_attr_max_indicator_brightness.attr,
>> +       NULL,
>> +};
>> +
>> +static struct attribute *led_flash_timeout_attrs[] = {
>> +       &dev_attr_flash_timeout.attr,
>> +       &dev_attr_max_flash_timeout.attr,
>> +       NULL,
>> +};
>> +
>> +static struct attribute *led_flash_brightness_attrs[] = {
>> +       &dev_attr_flash_brightness.attr,
>> +       &dev_attr_max_flash_brightness.attr,
>> +       NULL,
>> +};
>> +
>> +static struct attribute *led_flash_fault_attrs[] = {
>> +       &dev_attr_flash_fault.attr,
>> +       NULL,
>> +};
>> +
>> +static struct attribute_group led_flash_strobe_group = {
>> +       .attrs = led_flash_strobe_attrs,
>> +};
>> +
>> +static struct attribute_group led_flash_brightness_group = {
>> +       .attrs = led_flash_brightness_attrs,
>> +};
>> +
>> +static struct attribute_group led_flash_timeout_group = {
>> +       .attrs = led_flash_timeout_attrs,
>> +};
>> +
>> +static struct attribute_group led_flash_indicator_group = {
>> +       .attrs = led_flash_indicator_attrs,
>> +};
>> +
>> +static struct attribute_group led_flash_fault_group = {
>> +       .attrs = led_flash_fault_attrs,
>> +};
>> +
>> +static void led_flash_resume(struct led_classdev *led_cdev)
>> +{
>> +       struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
>> +
>> +       call_flash_op(flash, flash_brightness_set, flash->brightness.val);
>> +       call_flash_op(flash, timeout_set, flash->timeout.val);
>> +       call_flash_op(flash, indicator_brightness_set,
>> +                               flash->indicator_brightness->val);
>> +}
>> +
>> +static void led_flash_remove_sysfs_groups(struct led_classdev_flash *flash)
>> +{
>> +       struct led_classdev *led_cdev = &flash->led_cdev;
>> +       int i;
>> +
>> +       for (i = 0; i < LED_FLASH_MAX_SYSFS_GROUPS; ++i)
>> +               if (flash->sysfs_groups[i])
>> +                       sysfs_remove_group(&led_cdev->dev->kobj,
>> +                                               flash->sysfs_groups[i]);
>> +}
>> +
>> +static int led_flash_create_sysfs_groups(struct led_classdev_flash *flash)
>> +{
>> +       struct led_classdev *led_cdev = &flash->led_cdev;
>> +       const struct led_flash_ops *ops = flash->ops;
>> +       int ret, num_sysfs_groups = 0;
>> +
>> +       memset(flash->sysfs_groups, 0, sizeof(*flash->sysfs_groups) *
>> +                                               LED_FLASH_MAX_SYSFS_GROUPS);
>> +
>> +       ret = sysfs_create_group(&led_cdev->dev->kobj, &led_flash_strobe_group);
>> +       if (ret < 0)
>> +               goto err_create_group;
>> +       flash->sysfs_groups[num_sysfs_groups++] = &led_flash_strobe_group;
>> +
>> +       if (flash->indicator_brightness) {
>> +               ret = sysfs_create_group(&led_cdev->dev->kobj,
>> +                                       &led_flash_indicator_group);
>> +               if (ret < 0)
>> +                       goto err_create_group;
>> +               flash->sysfs_groups[num_sysfs_groups++] =
>> +                                       &led_flash_indicator_group;
>> +       }
>> +
>> +       if (ops->flash_brightness_set) {
>> +               ret = sysfs_create_group(&led_cdev->dev->kobj,
>> +                                       &led_flash_brightness_group);
>> +               if (ret < 0)
>> +                       goto err_create_group;
>> +               flash->sysfs_groups[num_sysfs_groups++] =
>> +                                       &led_flash_brightness_group;
>> +       }
>> +
>> +       if (ops->timeout_set) {
>> +               ret = sysfs_create_group(&led_cdev->dev->kobj,
>> +                                       &led_flash_timeout_group);
>> +               if (ret < 0)
>> +                       goto err_create_group;
>> +               flash->sysfs_groups[num_sysfs_groups++] =
>> +                                       &led_flash_timeout_group;
>> +       }
>> +
>> +       if (ops->fault_get) {
>> +               ret = sysfs_create_group(&led_cdev->dev->kobj,
>> +                                       &led_flash_fault_group);
>> +               if (ret < 0)
>> +                       goto err_create_group;
>> +               flash->sysfs_groups[num_sysfs_groups++] =
>> +                                       &led_flash_fault_group;
>> +       }
>> +
>> +       return 0;
>> +
>> +err_create_group:
>> +       led_flash_remove_sysfs_groups(flash);
>> +       return ret;
>> +}
>> +
>> +int led_classdev_flash_register(struct device *parent,
>> +                               struct led_classdev_flash *flash,
>> +                               struct device_node *node)
>> +{
>> +       struct led_classdev *led_cdev;
>> +       const struct led_flash_ops *ops;
>> +       int ret = -EINVAL;
>> +
>> +       if (!flash)
>> +               return -EINVAL;
>> +
>> +       led_cdev = &flash->led_cdev;
>> +
>> +       /* Torch capability is default for every LED Flash Class device */
>> +       led_cdev->flags |= LED_DEV_CAP_TORCH;
>> +
>> +       if (led_cdev->flags & LED_DEV_CAP_FLASH) {
>> +               if (!led_cdev->torch_brightness_set)
>> +                       return -EINVAL;
>> +
>> +               ops = flash->ops;
>> +               if (!ops || !ops->strobe_set)
>> +                       return -EINVAL;
>> +
>> +               if ((led_cdev->flags & LED_DEV_CAP_INDICATOR) &&
>> +                   (!flash->indicator_brightness ||
>> +                    !ops->indicator_brightness_set))
>> +                       return -EINVAL;
>> +
>> +               led_cdev->flash_resume = led_flash_resume;
>> +       }
>> +
>> +       /* Register led class device */
>> +       ret = led_classdev_register(parent, led_cdev);
>> +       if (ret < 0)
>> +               return -EINVAL;
>> +
>> +       /* Create flash led specific sysfs attributes */
>> +       ret = led_flash_create_sysfs_groups(flash);
>> +       if (ret < 0)
>> +               goto err_create_sysfs_groups;
>> +
>
> Here might cause some race condition. Please check the commits
> commit d0d480cce8f522b37c2c1de38230fc9ad15fa506
> Author: Johan Hovold <johan@kernel.org>
> Date:   Wed Jun 25 10:08:44 2014 -0700
>
>      leds: add led-class attribute-group support
>
>      Allow led-class devices to be created with optional attribute groups.
>
>      This is needed in order to allow led drivers to create custom device
>      attributes in a race-free manner.
>
>      Signed-off-by: Johan Hovold <johan@kernel.org>
>      Signed-off-by: Bryan Wu <cooloney@gmail.com>
>
> And related fixes in drivers/leds/ recently.

OK, I will modify the code appropriately.

>> +       return 0;
>> +
>> +err_create_sysfs_groups:
>> +       led_classdev_unregister(led_cdev);
>> +
>> +       return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(led_classdev_flash_register);
>> +
>> +void led_classdev_flash_unregister(struct led_classdev_flash *flash)
>> +{
>> +       if (!flash)
>> +               return;
>> +
>> +       led_flash_remove_sysfs_groups(flash);
>> +       led_classdev_unregister(&flash->led_cdev);
>> +}
>> +EXPORT_SYMBOL_GPL(led_classdev_flash_unregister);
>> +
>> +int led_set_flash_strobe(struct led_classdev_flash *flash, bool state)
>> +{
>> +       return call_flash_op(flash, strobe_set, state);
>> +}
>> +EXPORT_SYMBOL_GPL(led_set_flash_strobe);
>> +
>> +int led_get_flash_strobe(struct led_classdev_flash *flash, bool *state)
>> +{
>> +       return call_flash_op(flash, strobe_get, state);
>> +}
>> +EXPORT_SYMBOL_GPL(led_get_flash_strobe);
>> +
>> +static void led_clamp_align(struct led_flash_setting *s)
>> +{
>> +       u32 v, offset;
>> +
>> +       v = s->val + s->step / 2;
>> +       v = clamp(v, s->min, s->max);
>> +       offset = v - s->min;
>> +       offset = s->step * (offset / s->step);
>> +       s->val = s->min + offset;
>> +}
>> +
>> +int led_set_flash_timeout(struct led_classdev_flash *flash, u32 timeout)
>> +{
>> +       struct led_classdev *led_cdev = &flash->led_cdev;
>> +       struct led_flash_setting *s = &flash->timeout;
>> +       int ret = 0;
>> +
>> +       s->val = timeout;
>> +       led_clamp_align(s);
>> +
>> +       if (!(led_cdev->flags & LED_SUSPENDED))
>> +               ret = call_flash_op(flash, timeout_set, s->val);
>> +
>> +       return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(led_set_flash_timeout);
>> +
>> +int led_get_flash_fault(struct led_classdev_flash *flash, u32 *fault)
>> +{
>> +       return call_flash_op(flash, fault_get, fault);
>> +}
>> +EXPORT_SYMBOL_GPL(led_get_flash_fault);
>> +
>> +int led_set_flash_brightness(struct led_classdev_flash *flash,
>> +                               u32 brightness)
>> +{
>> +       struct led_classdev *led_cdev = &flash->led_cdev;
>> +       struct led_flash_setting *s = &flash->brightness;
>> +       int ret = 0;
>> +
>> +       s->val = brightness;
>> +       led_clamp_align(s);
>> +
>> +       if (!(led_cdev->flags & LED_SUSPENDED))
>> +               ret = call_flash_op(flash, flash_brightness_set, s->val);
>> +
>> +       return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(led_set_flash_brightness);
>> +
>> +int led_update_flash_brightness(struct led_classdev_flash *flash)
>> +{
>> +       struct led_flash_setting *s = &flash->brightness;
>> +       u32 brightness;
>> +       int ret = 0;
>> +
>> +       if (has_flash_op(flash, flash_brightness_get)) {
> I think call_flash_op() will call has_flash_op() in your previous definitions.

call_flash_op fails when the op is not initialized. Since the op is
optional we don't want the led_update_flash_brightness to fail when
it is not defined. This is consistent with the way how
led_update_brightness works. The op presence is checked prior calling
it and success is reported even if it doesn't exist.
Relevant comment should probably be added here.

>> +               ret = call_flash_op(flash, flash_brightness_get,
>> +                                               &brightness);
>
>
>> +               if (ret < 0)
>> +                       return ret;
>> +               s->val = brightness;
>> +       }
>> +
>> +       return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(led_update_flash_brightness);
>> +
>> +int led_set_indicator_brightness(struct led_classdev_flash *flash,
>> +                                       u32 brightness)
>> +{
>> +       struct led_classdev *led_cdev = &flash->led_cdev;
>> +       struct led_flash_setting *s = flash->indicator_brightness;
>> +       int ret = 0;
>> +
>> +       if (!s)
>> +               return -EINVAL;
>> +
>> +       s->val = brightness;
>> +       led_clamp_align(s);
>> +
>> +       if (!(led_cdev->flags & LED_SUSPENDED))
>> +               ret = call_flash_op(flash, indicator_brightness_set, s->val);
>> +
>> +       return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(led_set_indicator_brightness);
>> +
>> +int led_update_indicator_brightness(struct led_classdev_flash *flash)
>> +{
>> +       struct led_flash_setting *s = flash->indicator_brightness;
>> +       u32 brightness;
>> +       int ret = 0;
>> +
>> +       if (!s)
>> +               return -EINVAL;
>> +
>> +       if (has_flash_op(flash, indicator_brightness_get)) {
>> +               ret = call_flash_op(flash, indicator_brightness_get,
>> +                                                       &brightness);
>> +               if (ret < 0)
>> +                       return ret;
>> +               s->val = brightness;
>> +       }
>> +
>> +       return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(led_update_indicator_brightness);
>> +
>> +MODULE_AUTHOR("Jacek Anaszewski <j.anaszewski@samsung.com>");
>> +MODULE_LICENSE("GPL");
>> +MODULE_DESCRIPTION("LED Flash Class Interface");
>> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
>> index 5a11a07..d398b87 100644
>> --- a/drivers/leds/led-class.c
>> +++ b/drivers/leds/led-class.c
>> @@ -183,6 +183,10 @@ EXPORT_SYMBOL_GPL(led_classdev_suspend);
>>   void led_classdev_resume(struct led_classdev *led_cdev)
>>   {
>>          led_cdev->brightness_set(led_cdev, led_cdev->brightness);
>> +
>> +       if (led_cdev->flash_resume)
>> +               led_cdev->flash_resume(led_cdev);
>> +
>>          led_cdev->flags &= ~LED_SUSPENDED;
>>   }
>>   EXPORT_SYMBOL_GPL(led_classdev_resume);
>> diff --git a/include/linux/led-class-flash.h b/include/linux/led-class-flash.h
>> new file mode 100644
>> index 0000000..fcc15ed
>> --- /dev/null
>> +++ b/include/linux/led-class-flash.h
>> @@ -0,0 +1,238 @@
>> +/*
>> + * LED Flash Class interface
>> + *
>> + * Copyright (C) 2014 Samsung Electronics Co., Ltd.
>> + * Author: Jacek Anaszewski <j.anaszewski@samsung.com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + */
>> +#ifndef __LINUX_FLASH_LEDS_H_INCLUDED
>> +#define __LINUX_FLASH_LEDS_H_INCLUDED
>> +
>> +#include <linux/leds.h>
>> +
>> +struct led_classdev_flash;
>> +struct device_node;
>> +
>> +/*
>> + * Supported led fault bits - must be kept in synch
>> + * with V4L2_FLASH_FAULT bits.
>> + */
>> +#define LED_FAULT_OVER_VOLTAGE          V4L2_FLASH_FAULT_OVER_VOLTAGE
>> +#define LED_FAULT_TIMEOUT               V4L2_FLASH_FAULT_TIMEOUT
>> +#define LED_FAULT_OVER_TEMPERATURE      V4L2_FLASH_FAULT_OVER_TEMPERATURE
>> +#define LED_FAULT_SHORT_CIRCUIT                 V4L2_FLASH_FAULT_SHORT_CIRCUIT
>> +#define LED_FAULT_OVER_CURRENT          V4L2_FLASH_FAULT_OVER_CURRENT
>> +#define LED_FAULT_INDICATOR             V4L2_FLASH_FAULT_INDICATOR
>> +#define LED_FAULT_UNDER_VOLTAGE                 V4L2_FLASH_FAULT_UNDER_VOLTAGE
>> +#define LED_FAULT_INPUT_VOLTAGE                 V4L2_FLASH_FAULT_INPUT_VOLTAGE
>> +#define LED_FAULT_LED_OVER_TEMPERATURE  V4L2_FLASH_OVER_TEMPERATURE
>> +
>> +#define LED_FLASH_MAX_SYSFS_GROUPS 5
>> +
>> +struct led_flash_ops {
>> +       /* set flash brightness */
>> +       int (*flash_brightness_set)(struct led_classdev_flash *flash,
>> +                                       u32 brightness);
>> +       /* get flash brightness */
>> +       int (*flash_brightness_get)(struct led_classdev_flash *flash,
>> +                                       u32 *brightness);
>> +       /* set flash indicator brightness */
>> +       int (*indicator_brightness_set)(struct led_classdev_flash *flash,
>> +                                       u32 brightness);
>> +       /* get flash indicator brightness */
>> +       int (*indicator_brightness_get)(struct led_classdev_flash *flash,
>> +                                       u32 *brightness);
>> +       /* set flash strobe state */
>> +       int (*strobe_set)(struct led_classdev_flash *flash, bool state);
>> +       /* get flash strobe state */
>> +       int (*strobe_get)(struct led_classdev_flash *flash, bool *state);
>> +       /* set flash timeout */
>> +       int (*timeout_set)(struct led_classdev_flash *flash, u32 timeout);
>> +       /* get the flash LED fault */
>> +       int (*fault_get)(struct led_classdev_flash *flash, u32 *fault);
>> +};
>> +
>> +/*
>> + * Current value of a flash setting along
>> + * with its constraints.
>> + */
>> +struct led_flash_setting {
>> +       /* maximum allowed value */
>> +       u32 min;
>> +       /* maximum allowed value */
>> +       u32 max;
>> +       /* step value */
>> +       u32 step;
>> +       /* current value */
>> +       u32 val;
>> +};
>> +
>> +/*
>> + * Aggregated flash settings - designed for ease
>> + * of passing initialization data to the clients
>> + * wrapping a LED Flash class device.
>> + */
>> +struct led_flash_config {
>> +       struct led_flash_setting torch_brightness;
>> +       struct led_flash_setting flash_brightness;
>> +       struct led_flash_setting indicator_brightness;
>> +       struct led_flash_setting flash_timeout;
>> +       u32 flash_faults;
>> +};
>> +
>> +struct led_classdev_flash {
>> +       /* led-flash-manager uses it to link flashes */
> I guess no more led-flash-manager, right?

Yes, this is stray code, I will remove it.

>> +       struct list_head list;
>> +       /* led class device */
>> +       struct led_classdev led_cdev;
>> +       /* flash led specific ops */
>> +       const struct led_flash_ops *ops;
>> +
>> +       /* flash sysfs groups */
>> +       struct attribute_group *sysfs_groups[LED_FLASH_MAX_SYSFS_GROUPS];
>> +
>> +       /* flash brightness value in microamperes along with its constraints */
>> +       struct led_flash_setting brightness;
>> +
>> +       /* timeout value in microseconds along with its constraints */
>> +       struct led_flash_setting timeout;
>> +
>> +       /*
>> +        * Indicator brightness value in microamperes along with
>> +        * its constraints - this is an optional setting and must
>> +        * be allocated by the driver if the device supports privacy
>> +        * indicator led.
>> +        */
>> +       struct led_flash_setting *indicator_brightness;
>> +};
>> +
>> +static inline struct led_classdev_flash *lcdev_to_flash(
>> +                                               struct led_classdev *lcdev)
>> +{
>> +       return container_of(lcdev, struct led_classdev_flash, led_cdev);
>> +}
>> +
>> +/**
>> + * led_classdev_flash_register - register a new object of led_classdev class
>> +                                with support for flash LEDs
>> + * @parent: the flash LED to register
>> + * @flash: the led_classdev_flash structure for this device
>> + * @node: device tree node of the LED Flash Class device - it must be
>> +         initialized if the device is to be registered in the flash manager
>> + *
>> + * Returns: 0 on success or negative error value on failure
>> + */
>> +int led_classdev_flash_register(struct device *parent,
>> +                               struct led_classdev_flash *flash,
>> +                               struct device_node *node);
>> +
>> +/**
>> + * led_classdev_flash_unregister - unregisters an object of led_classdev class
>> +                                  with support for flash LEDs
>> + * @flash: the flash LED to unregister
>> + *
>> + * Unregisters a previously registered via led_classdev_flash_register object
>> + */
>> +void led_classdev_flash_unregister(struct led_classdev_flash *flash);
>> +
>> +/**
>> + * led_set_flash_strobe - setup flash strobe
>> + * @flash: the flash LED to set strobe on
>> + * @state: 1 - strobe flash, 0 - stop flash strobe
>> + *
>> + * Setup flash strobe - trigger flash strobe
>> + *
>> + * Returns: 0 on success or negative error value on failure
>> + */
>> +extern int led_set_flash_strobe(struct led_classdev_flash *flash,
>> +                               bool state);
>> +
>> +/**
>> + * led_get_flash_strobe - get flash strobe status
>> + * @flash: the flash LED to query
>> + * @state: 1 - flash is strobing, 0 - flash is off
>> + *
>> + * Check whether the flash is strobing at the moment or not.
>> + *
>> +u* Returns: 0 on success or negative error value on failure
>> + */
>> +extern int led_get_flash_strobe(struct led_classdev_flash *flash,
>> +                               bool *state);
>> +/**
>> + * led_set_flash_brightness - set flash LED brightness
>> + * @flash: the flash LED to set
>> + * @brightness: the brightness to set it to
>> + *
>> + * Returns: 0 on success or negative error value on failure
>> + *
>> + * Set a flash LED's brightness.
>> + */
>> +extern int led_set_flash_brightness(struct led_classdev_flash *flash,
>> +                                       u32 brightness);
>> +
>> +/**
>> + * led_update_flash_brightness - update flash LED brightness
>> + * @flash: the flash LED to query
>> + *
>> + * Get a flash LED's current brightness and update led_flash->brightness
>> + * member with the obtained value.
>> + *
>> + * Returns: 0 on success or negative error value on failure
>> + */
>> +extern int led_update_flash_brightness(struct led_classdev_flash *flash);
>> +
>> +/**
>> + * led_set_flash_timeout - set flash LED timeout
>> + * @flash: the flash LED to set
>> + * @timeout: the flash timeout to set it to
>> + *
>> + * Set the flash strobe duration. The duration set by the driver
>> + * is returned in the timeout argument and may differ from the
>> + * one that was originally passed.
>> + *
>> + * Returns: 0 on success or negative error value on failure
>> + */
>> +extern int led_set_flash_timeout(struct led_classdev_flash *flash,
>> +                                       u32 timeout);
>> +
>> +/**
>> + * led_get_flash_fault - get the flash LED fault
>> + * @flash: the flash LED to query
>> + * @fault: bitmask containing flash faults
>> + *
>> + * Get the flash LED fault.
>> + *
>> + * Returns: 0 on success or negative error value on failure
>> + */
>> +extern int led_get_flash_fault(struct led_classdev_flash *flash,
>> +                                       u32 *fault);
>> +
>> +/**
>> + * led_set_indicator_brightness - set indicator LED brightness
>> + * @flash: the flash LED to set
>> + * @brightness: the brightness to set it to
>> + *
>> + * Set an indicator LED's brightness.
>> + *
>> + * Returns: 0 on success or negative error value on failure
>> + */
>> +extern int led_set_indicator_brightness(struct led_classdev_flash *flash,
>> +                                       u32 led_brightness);
>> +
>> +/**
>> + * led_update_indicator_brightness - update flash indicator LED brightness
>> + * @flash: the flash LED to query
>> + *
>> + * Get a flash indicator LED's current brightness and update
>> + * led_flash->indicator_brightness member with the obtained value.
>> + *
>> + * Returns: 0 on success or negative error value on failure
>> + */
>> +extern int led_update_indicator_brightness(struct led_classdev_flash *flash);
>> +
>> +
>> +#endif /* __LINUX_FLASH_LEDS_H_INCLUDED */
>> diff --git a/include/linux/leds.h b/include/linux/leds.h
>> index bc2a570..70fa0ad 100644
>> --- a/include/linux/leds.h
>> +++ b/include/linux/leds.h
>> @@ -45,6 +45,8 @@ struct led_classdev {
>>   #define LED_BLINK_INVERT       (1 << 19)
>>   #define LED_SYSFS_DISABLE      (1 << 20)
>>   #define LED_DEV_CAP_TORCH      (1 << 21)
>> +#define LED_DEV_CAP_FLASH      (1 << 22)
>> +#define LED_DEV_CAP_INDICATOR  (1 << 23)
>>
>>          /* Set LED brightness level */
>>          /* Must not sleep, use a workqueue if needed */
>> @@ -83,6 +85,7 @@ struct led_classdev {
>>          unsigned long            blink_delay_on, blink_delay_off;
>>          struct timer_list        blink_timer;
>>          int                      blink_brightness;
>> +       void                    (*flash_resume)(struct led_classdev *led_cdev);
>>
>>          struct work_struct      set_brightness_work;
>>          int                     delayed_set_value;
>> --
>> 1.7.9.5
>>
>