[PATCH 0/3] add new API to sysfs and device core code

[PATCH 0/3] add new API to sysfs and device core code

[Bryan Wu]

Send out a uevent when create file in sysfs, which is required by userspace
application such udev in Android

Bryan Wu (3):
  sysfs: introduce a sysfs_create_file_uevent new API
  drivers: add a new device_create_file_uevent API
  ledtrig-timer: convert to use device_create_file_uevent API

 drivers/base/core.c          | 19 +++++++++++++++++++
 drivers/leds/ledtrig-timer.c |  6 ++++--
 fs/sysfs/file.c              | 28 ++++++++++++++++++++++++++++
 include/linux/device.h       |  4 ++++
 include/linux/sysfs.h        | 13 +++++++++++++
 5 files changed, 68 insertions(+), 2 deletions(-)

-- 
1.7.11.1

[PATCH 1/3] sysfs: introduce a sysfs_create_file_uevent new API

[Bryan Wu]

Send a uevent notification whenever a new sysfs file is created to allow
userspace processes such as udev to modify permissions on the new files.

This new API function helps to do this.

Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
---
 fs/sysfs/file.c       | 28 ++++++++++++++++++++++++++++
 include/linux/sysfs.h | 13 +++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 00012e3..5a22d13 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -576,6 +576,34 @@ int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
 
 }
 
+/**
+ *	sysfs_create_file_uevent - create an attribute file for an object
+					and send a uevent to userspace.
+ *	@kobj:	object we're creating for.
+ *	@attr:	attribute descriptor.
+ *	@desc:  description about the uevent.
+ *	@action: kobject uevent action type.
+ */
+
+int sysfs_create_file_uevent(struct kobject *kobj, const struct attribute *attr,
+			const char *desc, enum kobject_action action)
+{
+	int err = 0;
+	char *envp[2];
+
+	BUG_ON(!kobj || !kobj->sd || !attr || !desc);
+
+	err = sysfs_add_file(kobj->sd, attr, SYSFS_KOBJ_ATTR);
+
+	if (desc) {
+		envp[0] = desc;
+		envp[1] = NULL;
+		kobject_uevent_env(kobj, action, envp);
+	}
+
+	return err;
+}
+
 int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
 {
 	int err = 0;
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 381f06d..0054d41 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -22,6 +22,7 @@
 struct kobject;
 struct module;
 enum kobj_ns_type;
+enum kobject_action;
 
 struct attribute {
 	const char		*name;
@@ -142,6 +143,10 @@ int __must_check sysfs_move_dir(struct kobject *kobj,
 
 int __must_check sysfs_create_file(struct kobject *kobj,
 				   const struct attribute *attr);
+int __must_check sysfs_create_file_uevent(struct kobject * kobj,
+				const struct attribute * attr,
+				const char * desc,
+				enum kobject_action action);
 int __must_check sysfs_create_files(struct kobject *kobj,
 				   const struct attribute **attr);
 int __must_check sysfs_chmod_file(struct kobject *kobj,
@@ -226,6 +231,14 @@ static inline int sysfs_create_file(struct kobject *kobj,
 	return 0;
 }
 
+static inline int sysfs_create_file_uevent(struct kobject * kobj,
+					const struct attribute * attr,
+					const char *desc,
+					enum kobject_action action)
+{
+	return 0;
+}
+
 static inline int sysfs_create_files(struct kobject *kobj,
 				    const struct attribute **attr)
 {
-- 
1.7.11.1

Re: [PATCH 1/3] sysfs: introduce a sysfs_create_file_uevent new API

[Greg KH]

On Fri, Jul 27, 2012 at 12:02:41PM +0800, Bryan Wu wrote:
> Send a uevent notification whenever a new sysfs file is created to allow
> userspace processes such as udev to modify permissions on the new files.

This makes no sense, why not just call kobject_uevent after creating the
file when needed?  Wrapping it up in a single function call doesn't add
any benefit that I can see, can you?

> 
> This new API function helps to do this.
> 
> Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
> ---
>  fs/sysfs/file.c       | 28 ++++++++++++++++++++++++++++
>  include/linux/sysfs.h | 13 +++++++++++++
>  2 files changed, 41 insertions(+)
> 
> diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
> index 00012e3..5a22d13 100644
> --- a/fs/sysfs/file.c
> +++ b/fs/sysfs/file.c
> @@ -576,6 +576,34 @@ int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
>  
>  }
>  
> +/**
> + *	sysfs_create_file_uevent - create an attribute file for an object
> +					and send a uevent to userspace.

kerneldoc needs to be on one line for function names, right?

greg k-h

Re: [PATCH 1/3] sysfs: introduce a sysfs_create_file_uevent new API

[Bryan Wu]

On Fri, Jul 27, 2012 at 11:52 PM, Greg KH <gregkh@linuxfoundation.org> wrote:
> On Fri, Jul 27, 2012 at 12:02:41PM +0800, Bryan Wu wrote:
>> Send a uevent notification whenever a new sysfs file is created to allow
>> userspace processes such as udev to modify permissions on the new files.
>
> This makes no sense, why not just call kobject_uevent after creating the
> file when needed?  Wrapping it up in a single function call doesn't add
> any benefit that I can see, can you?
>

I actually just want to make it benefit for further similar issue in
other subsystem, although I got this point from the email started by
Colin Cross. I agree if it is just specific to LED subsystem, we'd
better add this fixing in LED trigger core code. Maybe I worried about
too much and if you guys all ack Colin's patch, I'm going to apply it.

Thanks,
-Bryan

>>
>> This new API function helps to do this.
>>
>> Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
>> ---
>>  fs/sysfs/file.c       | 28 ++++++++++++++++++++++++++++
>>  include/linux/sysfs.h | 13 +++++++++++++
>>  2 files changed, 41 insertions(+)
>>
>> diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
>> index 00012e3..5a22d13 100644
>> --- a/fs/sysfs/file.c
>> +++ b/fs/sysfs/file.c
>> @@ -576,6 +576,34 @@ int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
>>
>>  }
>>
>> +/**
>> + *   sysfs_create_file_uevent - create an attribute file for an object
>> +                                     and send a uevent to userspace.
>
> kerneldoc needs to be on one line for function names, right?
>
> greg k-h



-- 
Bryan Wu <bryan.wu@canonical.com>
Kernel Developer    +86.186-168-78255 Mobile
Canonical Ltd.      www.canonical.com
Ubuntu - Linux for human beings | www.ubuntu.com

[PATCH 2/3] drivers: add a new device_create_file_uevent API

[Bryan Wu]

This will use sysfs_create_file_uevent to create a sysfs file and send out
a uevent to userspace application such as udev.

Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
---
 drivers/base/core.c    | 19 +++++++++++++++++++
 include/linux/device.h |  4 ++++
 2 files changed, 23 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 346be8b..62fd266 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -538,6 +538,25 @@ int device_create_file(struct device *dev,
 }
 
 /**
+ * device_create_file_uevent - create sysfs attribute file for device
+ *				and send a uevent to userspace.
+ * @dev: device.
+ * @attr: device attribute descriptor.
+ * @desc: description about the uevent.
+ * @action: kobject uevent action type.
+ */
+int device_create_file_uevent(struct device *dev,
+		       const struct device_attribute *attr,
+		       const char *desc,
+		       enum kobject_action action)
+{
+	int error = 0;
+	if (dev)
+		error = sysfs_create_file_uevent(&dev->kobj, &attr->attr,
+						 desc, action);
+	return error;
+}
+/**
  * device_remove_file - remove sysfs attribute file.
  * @dev: device.
  * @attr: device attribute descriptor.
diff --git a/include/linux/device.h b/include/linux/device.h
index 6de9415..d1545f3 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -510,6 +510,10 @@ ssize_t device_store_int(struct device *dev, struct device_attribute *attr,
 
 extern int device_create_file(struct device *device,
 			      const struct device_attribute *entry);
+extern int device_create_file_uevent(struct device *dev,
+				const struct device_attribute *attr,
+			       const char *desc,
+			       enum kobject_action action);
 extern void device_remove_file(struct device *dev,
 			       const struct device_attribute *attr);
 extern int __must_check device_create_bin_file(struct device *dev,
-- 
1.7.11.1

[PATCH 3/3] ledtrig-timer: convert to use device_create_file_uevent API

[Bryan Wu]

To send KOBJ_CHANGE uevent to userspace which is required by Android

Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
---
 drivers/leds/ledtrig-timer.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/ledtrig-timer.c b/drivers/leds/ledtrig-timer.c
index 9010f7a..d8b6296 100644
--- a/drivers/leds/ledtrig-timer.c
+++ b/drivers/leds/ledtrig-timer.c
@@ -78,10 +78,12 @@ static void timer_trig_activate(struct led_classdev *led_cdev)
 
 	led_cdev->trigger_data = NULL;
 
-	rc = device_create_file(led_cdev->dev, &dev_attr_delay_on);
+	rc = device_create_file_uevent(led_cdev->dev, &dev_attr_delay_on,
+				"TRIGGER=timer", KOBJ_CHANGE);
 	if (rc)
 		return;
-	rc = device_create_file(led_cdev->dev, &dev_attr_delay_off);
+	rc = device_create_file_uevent(led_cdev->dev, &dev_attr_delay_off,
+				"TRIGGER=timer", KOBJ_CHANGE);
 	if (rc)
 		goto err_out_delayon;
 
-- 
1.7.11.1

Re: [PATCH 0/3] add new API to sysfs and device core code

[Greg KH]

On Fri, Jul 27, 2012 at 12:02:40PM +0800, Bryan Wu wrote:
> Send out a uevent when create file in sysfs, which is required by userspace
> application such udev in Android

There is no such thing as "udev in Android" the last time I looked.

Has this changed?

Re: [PATCH 0/3] add new API to sysfs and device core code

[Colin Cross]

On Fri, Jul 27, 2012 at 8:50 AM, Greg KH <gregkh@linuxfoundation.org> wrote:
> On Fri, Jul 27, 2012 at 12:02:40PM +0800, Bryan Wu wrote:
>> Send out a uevent when create file in sysfs, which is required by userspace
>> application such udev in Android
>
> There is no such thing as "udev in Android" the last time I looked.
>
> Has this changed?

Android does not use udev, but it does have a daemon that listens for
uevents (ueventd).  I used udev in my previous examples because the
issue is not specific to Android.