Re: [PATCH/RFC v8 01/14] leds: Add LED Flash class extension to the LED subsystem

[Jacek Anaszewski <j.anaszewski@samsung.com>]

On 12/05/2014 08:27 PM, Bryan Wu wrote:
> On Fri, Nov 28, 2014 at 1:17 AM, Jacek Anaszewski
> <j.anaszewski@samsung.com> wrote:
>> 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
>> and flash_sync_strobe. All the flash related features are placed
>> in a separate module. Torch mode is supported by the LED class
>> interface.
>>
>> 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            |   10 +
>>   drivers/leds/Makefile           |    1 +
>>   drivers/leds/led-class-flash.c  |  446 +++++++++++++++++++++++++++++++++++++++
>>   drivers/leds/led-class.c        |    4 +
>>   include/linux/led-class-flash.h |  198 +++++++++++++++++
>>   include/linux/leds.h            |    3 +
>>   6 files changed, 662 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 b3c0d8a..fa8021e 100644
>> --- a/drivers/leds/Kconfig
>> +++ b/drivers/leds/Kconfig
>> @@ -19,6 +19,16 @@ 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
>
> Looks like it requires V4L2, so probably add depends on V4L2 or similar.
> But actually I want to see LED Flash class doesn't depends on V4L2. Is
> that possible to do that?
> For example a non-V4L2 application want to control the LED as a flash?

It doesn't require V4L2. It only used v4l2-controls.h for error code
macros, but this is also going to be changed.

> Other than this main concern, I'm good with this patch now.
>
> -Bryan
>
>> +       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 1c65a19..cbba921 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..219b414
>> --- /dev/null
>> +++ b/drivers/leds/led-class-flash.c
>> @@ -0,0 +1,446 @@
>> +/*
>> + * 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/led-class-flash.h>
>> +#include <linux/leds.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 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 ssize_t flash_sync_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 sync_strobe;
>> +       ssize_t ret;
>> +
>> +       mutex_lock(&led_cdev->led_access);
>> +
>> +       if (led_sysfs_is_disabled(led_cdev)) {
>> +               ret = -EBUSY;
>> +               goto unlock;
>> +       }
>> +
>> +       ret = kstrtoul(buf, 10, &sync_strobe);
>> +       if (ret)
>> +               goto unlock;
>> +
>> +       flash->sync_strobe = sync_strobe;
>> +
>> +       ret = size;
>> +unlock:
>> +       mutex_unlock(&led_cdev->led_access);
>> +       return ret;
>> +}
>> +
>> +static ssize_t flash_sync_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);
>> +
>> +       return sprintf(buf, "%u\n", flash->sync_strobe);
>> +}
>> +static DEVICE_ATTR_RW(flash_sync_strobe);
>> +
>> +static struct attribute *led_flash_strobe_attrs[] = {
>> +       &dev_attr_flash_strobe.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 *led_flash_sync_strobe_attrs[] = {
>> +       &dev_attr_flash_sync_strobe.attr,
>> +       NULL,
>> +};
>> +
>> +static const struct attribute_group led_flash_strobe_group = {
>> +       .attrs = led_flash_strobe_attrs,
>> +};
>> +
>> +static const struct attribute_group led_flash_timeout_group = {
>> +       .attrs = led_flash_timeout_attrs,
>> +};
>> +
>> +static const struct attribute_group led_flash_brightness_group = {
>> +       .attrs = led_flash_brightness_attrs,
>> +};
>> +
>> +static const struct attribute_group led_flash_fault_group = {
>> +       .attrs = led_flash_fault_attrs,
>> +};
>> +
>> +static const struct attribute_group led_flash_sync_strobe_group = {
>> +       .attrs = led_flash_sync_strobe_attrs,
>> +};
>> +
>> +static const struct attribute_group *flash_groups[] = {
>> +       &led_flash_strobe_group,
>> +       NULL,
>> +       NULL,
>> +       NULL,
>> +       NULL,
>> +       NULL,
>> +       NULL
>> +};
>> +
>> +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);
>> +}
>> +
>> +static void led_flash_init_sysfs_groups(struct led_classdev_flash *flash)
>> +{
>> +       struct led_classdev *led_cdev = &flash->led_cdev;
>> +       const struct led_flash_ops *ops = flash->ops;
>> +       int num_sysfs_groups = 1;
>> +
>> +       if (ops->flash_brightness_set)
>> +               flash_groups[num_sysfs_groups++] = &led_flash_brightness_group;
>> +
>> +       if (ops->timeout_set)
>> +               flash_groups[num_sysfs_groups++] = &led_flash_timeout_group;
>> +
>> +       if (ops->fault_get)
>> +               flash_groups[num_sysfs_groups++] = &led_flash_fault_group;
>> +
>> +       if (led_cdev->flags & LED_DEV_CAP_COMPOUND)
>> +               flash_groups[num_sysfs_groups++] = &led_flash_sync_strobe_group;
>> +
>> +       led_cdev->groups = flash_groups;
>> +}
>> +
>> +int led_classdev_flash_register(struct device *parent,
>> +                               struct led_classdev_flash *flash)
>> +{
>> +       struct led_classdev *led_cdev;
>> +       const struct led_flash_ops *ops;
>> +       int ret;
>> +
>> +       if (!flash)
>> +               return -EINVAL;
>> +
>> +       led_cdev = &flash->led_cdev;
>> +
>> +       if (led_cdev->flags & LED_DEV_CAP_FLASH) {
>> +               if (!led_cdev->brightness_set_sync)
>> +                       return -EINVAL;
>> +
>> +               ops = flash->ops;
>> +               if (!ops || !ops->strobe_set)
>> +                       return -EINVAL;
>> +
>> +               led_cdev->flash_resume = led_flash_resume;
>> +
>> +               /* Select the sysfs attributes to be created for the device */
>> +               led_flash_init_sysfs_groups(flash);
>> +       }
>> +
>> +       /* Register led class device */
>> +       ret = led_classdev_register(parent, led_cdev);
>> +       if (ret < 0)
>> +               return ret;
>> +
>> +       /* Setting a torch brightness needs to have immediate effect */
>> +       led_cdev->flags &= ~SET_BRIGHTNESS_ASYNC;
>> +       led_cdev->flags |= SET_BRIGHTNESS_SYNC;
>> +
>> +       return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(led_classdev_flash_register);
>> +
>> +void led_classdev_flash_unregister(struct led_classdev_flash *flash)
>> +{
>> +       if (!flash)
>> +               return;
>> +
>> +       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;
>> +
>> +       s->val = timeout;
>> +       led_clamp_align(s);
>> +
>> +       if (!(led_cdev->flags & LED_SUSPENDED))
>> +               return call_flash_op(flash, timeout_set, s->val);
>> +
>> +       return 0;
>> +}
>> +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;
>> +
>> +       s->val = brightness;
>> +       led_clamp_align(s);
>> +
>> +       if (!(led_cdev->flags & LED_SUSPENDED))
>> +               return call_flash_op(flash, flash_brightness_set, s->val);
>> +
>> +       return 0;
>> +}
>> +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;
>> +
>> +       if (has_flash_op(flash, flash_brightness_get)) {
>> +               int ret = call_flash_op(flash, flash_brightness_get,
>> +                                               &brightness);
>> +               if (ret < 0)
>> +                       return ret;
>> +
>> +               s->val = brightness;
>> +       }
>> +
>> +       return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(led_update_flash_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 dbeebac..02564c5 100644
>> --- a/drivers/leds/led-class.c
>> +++ b/drivers/leds/led-class.c
>> @@ -179,6 +179,10 @@ 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..5188d9fd
>> --- /dev/null
>> +++ b/include/linux/led-class-flash.h
>> @@ -0,0 +1,198 @@
>> +/*
>> + * 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>
>> +#include <uapi/linux/v4l2-controls.h>
>> +
>> +struct device_node;
>> +struct led_classdev_flash;
>> +
>> +/*
>> + * 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
>> +
>
> I suggest we move those V4L2_FLASH_FAULT_* to our LED subsystem as LED_FAULT_*.
> Then V4L2 Flash control code should include that LED header file and
> #define V4L2_FLASH_FAULT_* LED_FAULT_*
>
> Because this flash fault feature is for LED actually not for V4L2.
>
> Then we can decouple V4L2 and LED Flash class driver here.

I'm OK with it. Sakari, what do you think about spinning it the other
way round - V4L2 will use LED Flash class fault definitions?

>> +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 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 flash_timeout;
>> +       u32 flash_faults;
>> +};
>> +
>> +struct led_classdev_flash {
>> +       /* led class device */
>> +       struct led_classdev led_cdev;
>> +
>> +       /* flash led specific ops */
>> +       const struct led_flash_ops *ops;
>> +
>> +       /* flash brightness value in microamperes along with its constraints */
>> +       struct led_flash_setting brightness;
>> +
>> +       /* flash timeout value in microseconds along with its constraints */
>> +       struct led_flash_setting timeout;
>> +
>> +       /*
>> +        * Indicates whether the flash sub-led should strobe
>> +        * upon strobe activation on any of the remaining sub-leds.
>> +        */
>> +       bool sync_strobe:1;
>> +};
>> +
>> +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
>> + *
>> + * Returns: 0 on success or negative error value on failure
>> + */
>> +int led_classdev_flash_register(struct device *parent,
>> +                               struct led_classdev_flash *flash);
>> +
>> +/**
>> + * led_classdev_flash_unregister - unregisters an object of led_classdev class
>> + *                                with support for flash LEDs
>> + * @flash: the flash LED to unregister
>> + *
>> + * Unregister 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
>> + *
>> + * Strobe the flash LED.
>> + *
>> + * 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.
>> + *
>> + * 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
>> + *
>> + * Set a flash LED's brightness.
>> + *
>> + * Returns: 0 on success or negative error value on failure
>> + */
>> +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);
>> +
>> +#endif /* __LINUX_FLASH_LEDS_H_INCLUDED */
>> diff --git a/include/linux/leds.h b/include/linux/leds.h
>> index cfceef3..c359f35 100644
>> --- a/include/linux/leds.h
>> +++ b/include/linux/leds.h
>> @@ -46,6 +46,8 @@ struct led_classdev {
>>   #define LED_SYSFS_DISABLE      (1 << 20)
>>   #define SET_BRIGHTNESS_ASYNC   (1 << 21)
>>   #define SET_BRIGHTNESS_SYNC    (1 << 22)
>> +#define LED_DEV_CAP_FLASH      (1 << 23)
>> +#define LED_DEV_CAP_COMPOUND   (1 << 24)
>>
> What's the use case of CAP_COMPOUND?

It signifies that the device controls many sub-leds and the sub-leds
will expose flash_strobe_sync sysfs attribute for strobing the flash
synchronously with the other sub-leds. Please see the driver for
MAX77693.

>>          /* Set LED brightness level */
>>          /* Must not sleep, use a workqueue if needed */
>> @@ -81,6 +83,7 @@ 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
>>
>

Best Regards,
Jacek Anaszewski