Re: [PATCH/RFC v3 1/5] leds: Add sysfs and kernel internal API for flash LEDs

[Sakari Ailus]

Hi Jacek,

Thanks for the update! Some comments below. I'll try to reply to the rest
during the coming days.

On Fri, Apr 11, 2014 at 04:56:52PM +0200, Jacek Anaszewski 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
> optional external_strobe, indicator_brightness and
> max_indicator_btightness. 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@xxxxxxxxxxx>
> Acked-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> Cc: Bryan Wu <cooloney@xxxxxxxxx>
> Cc: Richard Purdie <rpurdie@xxxxxxxxx>
> ---
>  drivers/leds/Kconfig        |    8 +
>  drivers/leds/Makefile       |    1 +
>  drivers/leds/led-class.c    |   36 ++-
>  drivers/leds/led-flash.c    |  627 +++++++++++++++++++++++++++++++++++++++++++
>  drivers/leds/led-triggers.c |   16 +-
>  drivers/leds/leds.h         |    6 +
>  include/linux/leds.h        |   50 +++-
>  include/linux/leds_flash.h  |  252 +++++++++++++++++
>  8 files changed, 982 insertions(+), 14 deletions(-)
>  create mode 100644 drivers/leds/led-flash.c
>  create mode 100644 include/linux/leds_flash.h
> 
> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> index 2062682..1e1c81f 100644
> --- a/drivers/leds/Kconfig
> +++ b/drivers/leds/Kconfig
> @@ -19,6 +19,14 @@ 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 "Flash LEDs Support"
> +	depends on LEDS_CLASS
> +	help
> +	  This option enables support for flash LED devices. Say Y if you
> +	  want to use flash specific features of a LED device, if they
> +	  are supported.
> +
>  comment "LED drivers"
>  
>  config LEDS_88PM860X
> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
> index 3cd76db..8861b86 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-$(CONFIG_LEDS_CLASS_FLASH)		+= led-flash.o
>  obj-$(CONFIG_LEDS_TRIGGERS)		+= led-triggers.o
>  
>  # LED Platform Drivers
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index f37d63c..58f16c3 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -9,15 +9,16 @@
>   * published by the Free Software Foundation.
>   */
>  
> -#include <linux/module.h>
> -#include <linux/kernel.h>
> +#include <linux/ctype.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
>  #include <linux/init.h>
> +#include <linux/kernel.h>
>  #include <linux/list.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
>  #include <linux/spinlock.h>
> -#include <linux/device.h>
>  #include <linux/timer.h>
> -#include <linux/err.h>
> -#include <linux/ctype.h>
>  #include <linux/leds.h>
>  #include "leds.h"
>  
> @@ -45,28 +46,38 @@ 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_lock);
> +
> +	if (led_sysfs_is_locked(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);
> +	ret = size;
>  
> -	return size;
> +unlock:
> +	mutex_unlock(&led_cdev->led_lock);
> +	return ret;
>  }
>  static DEVICE_ATTR_RW(brightness);
>  
> -static ssize_t led_max_brightness_show(struct device *dev,
> +static ssize_t max_brightness_show(struct device *dev,
>  		struct device_attribute *attr, char *buf)
>  {
>  	struct led_classdev *led_cdev = dev_get_drvdata(dev);
>  
>  	return sprintf(buf, "%u\n", led_cdev->max_brightness);
>  }
> -static DEVICE_ATTR(max_brightness, 0444, led_max_brightness_show, NULL);
> +static DEVICE_ATTR_RO(max_brightness);
>  
>  #ifdef CONFIG_LEDS_TRIGGERS
>  static DEVICE_ATTR(trigger, 0644, led_trigger_show, led_trigger_store);
> @@ -174,6 +185,8 @@ 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);
> @@ -218,6 +231,7 @@ 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_lock);
>  	/* add to the list of leds */
>  	down_write(&leds_list_lock);
>  	list_add_tail(&led_cdev->node, &leds_list);
> @@ -271,6 +285,8 @@ 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_lock);
>  }
>  EXPORT_SYMBOL_GPL(led_classdev_unregister);
>  
> diff --git a/drivers/leds/led-flash.c b/drivers/leds/led-flash.c
> new file mode 100644
> index 0000000..9d482a4
> --- /dev/null
> +++ b/drivers/leds/led-flash.c
> @@ -0,0 +1,627 @@
> +/*
> + * LED Class Flash interface
> + *
> + * Copyright (C) 2014 Samsung Electronics Co., Ltd.
> + * Author: Jacek Anaszewski <j.anaszewski@xxxxxxxxxxx>
> + *
> + * 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/module.h>
> +#include <linux/leds.h>
> +#include <linux/leds_flash.h>
> +#include "leds.h"
> +
> +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);
> +	unsigned long state;
> +	ssize_t ret;
> +
> +	mutex_lock(&led_cdev->led_lock);
> +
> +	if (led_sysfs_is_locked(led_cdev)) {
> +		ret = -EBUSY;
> +		goto unlock;
> +	}
> +
> +	ret = kstrtoul(buf, 10, &state);
> +	if (ret)
> +		goto unlock;
> +
> +	ret = led_set_flash_brightness(led_cdev, state);
> +	if (ret < 0)
> +		goto unlock;
> +
> +	ret = size;
> +unlock:
> +	mutex_unlock(&led_cdev->led_lock);
> +	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_flash *flash = led_cdev->flash;
> +
> +	/* no lock needed for this */
> +	led_update_flash_brightness(led_cdev);
> +
> +	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_flash *flash = led_cdev->flash;
> +
> +	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);
> +	unsigned long state;
> +	ssize_t ret;
> +
> +	mutex_lock(&led_cdev->led_lock);
> +
> +	if (led_sysfs_is_locked(led_cdev)) {
> +		ret = -EBUSY;
> +		goto unlock;
> +	}
> +
> +	ret = kstrtoul(buf, 10, &state);
> +	if (ret)
> +		goto unlock;
> +
> +	ret = led_set_indicator_brightness(led_cdev, state);
> +	if (ret < 0)
> +		goto unlock;
> +
> +	ret = size;
> +unlock:
> +	mutex_unlock(&led_cdev->led_lock);
> +	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_flash *flash = led_cdev->flash;
> +
> +	/* no lock needed for this */
> +	led_update_indicator_brightness(led_cdev);
> +
> +	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_flash *flash = led_cdev->flash;
> +
> +	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);
> +	unsigned long state;
> +	ssize_t ret;
> +
> +	mutex_lock(&led_cdev->led_lock);
> +
> +	if (led_sysfs_is_locked(led_cdev)) {
> +		ret = -EBUSY;
> +		goto unlock;
> +	}
> +
> +	ret = kstrtoul(buf, 10, &state);
> +	if (ret)
> +		goto unlock;
> +
> +	if (state < 0 || state > 1)
> +		return -EINVAL;

How about assigning ret and a goto instead? :-)

> +	ret = led_set_flash_strobe(led_cdev, state);
> +	if (ret < 0)
> +		goto unlock;
> +	ret = size;
> +unlock:
> +	mutex_unlock(&led_cdev->led_lock);
> +	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);
> +	int ret;
> +
> +	/* no lock needed for this */
> +	ret = led_get_flash_strobe(led_cdev);
> +	if (ret < 0)
> +		return ret;
> +
> +	return sprintf(buf, "%u\n", ret);
> +}
> +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);
> +	unsigned long flash_timeout;
> +	ssize_t ret;
> +
> +	mutex_lock(&led_cdev->led_lock);
> +
> +	if (led_sysfs_is_locked(led_cdev)) {
> +		ret = -EBUSY;
> +		goto unlock;
> +	}
> +
> +	ret = kstrtoul(buf, 10, &flash_timeout);
> +	if (ret)
> +		goto unlock;
> +
> +	ret = led_set_flash_timeout(led_cdev, flash_timeout);
> +	if (ret < 0)
> +		goto unlock;
> +
> +	ret = size;
> +unlock:
> +	mutex_unlock(&led_cdev->led_lock);
> +	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_flash *flash = led_cdev->flash;
> +
> +	return sprintf(buf, "%d\n", flash->timeout.val);

val is unsigned.

> +}
> +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_flash *flash = led_cdev->flash;
> +
> +	return sprintf(buf, "%d\n", flash->timeout.max);

Same here (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);
> +	unsigned int fault;

As led_get_flash_fault() expects a u32, it'd be cleaner to use that for
passing a reference.

> +	int ret;
> +
> +	ret = led_get_flash_fault(led_cdev, &fault);
> +	if (ret < 0)
> +		return -EINVAL;
> +
> +	return sprintf(buf, "0x%8.8x\n", fault);
> +}
> +static DEVICE_ATTR_RO(flash_fault);
> +
> +static ssize_t external_strobe_store(struct device *dev,
> +		struct device_attribute *attr, const char *buf, size_t size)
> +{
> +	struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +	unsigned long external_strobe;
> +	ssize_t ret;
> +
> +	mutex_lock(&led_cdev->led_lock);
> +
> +	if (led_sysfs_is_locked(led_cdev)) {
> +		ret = -EBUSY;
> +		goto unlock;
> +	}
> +
> +	ret = kstrtoul(buf, 10, &external_strobe);
> +	if (ret)
> +		goto unlock;
> +
> +	if (external_strobe > 1) {
> +		ret = -EINVAL;
> +		goto unlock;
> +	}
> +
> +	ret = led_set_external_strobe(led_cdev, external_strobe);
> +	if (ret < 0)
> +		goto unlock;
> +	ret = size;
> +unlock:
> +	mutex_unlock(&led_cdev->led_lock);
> +	return ret;
> +}
> +
> +static ssize_t external_strobe_show(struct device *dev,
> +		struct device_attribute *attr, char *buf)
> +{
> +	struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +
> +	return sprintf(buf, "%u\n", led_cdev->flash->external_strobe);
> +}
> +static DEVICE_ATTR_RW(external_strobe);
> +
> +static struct attribute *led_flash_attrs[] = {
> +	&dev_attr_flash_brightness.attr,
> +	&dev_attr_flash_strobe.attr,
> +	&dev_attr_flash_timeout.attr,
> +	&dev_attr_max_flash_timeout.attr,
> +	&dev_attr_max_flash_brightness.attr,
> +	&dev_attr_flash_fault.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_external_strobe_attrs[] = {
> +	&dev_attr_external_strobe.attr,
> +	NULL,
> +};
> +
> +static struct attribute_group led_flash_group = {
> +	.attrs = led_flash_attrs,
> +};
> +
> +static struct attribute_group led_flash_indicator_group = {
> +	.attrs = led_flash_indicator_attrs,
> +};
> +
> +static struct attribute_group led_flash_external_strobe_group = {
> +	.attrs = led_flash_external_strobe_attrs,
> +};
> +
> +void led_flash_resume(struct led_classdev *led_cdev)
> +{
> +	struct led_flash *flash = led_cdev->flash;
> +
> +	call_flash_op(brightness_set, led_cdev,
> +				flash->brightness.val);
> +	call_flash_op(timeout_set, led_cdev,
> +				flash->timeout.val);

Both fit on a single line.

> +	if (has_flash_op(indicator_brightness_set))
> +		call_flash_op(indicator_brightness_set, led_cdev,
> +				flash->indicator_brightness->val);
> +}
> +
> +#ifdef CONFIG_V4L2_FLASH
> +static const struct v4l2_flash_ops v4l2_flash_ops = {
> +	.brightness_set = led_set_brightness,
> +	.brightness_update = led_update_brightness,
> +	.flash_brightness_set = led_set_flash_brightness,
> +	.flash_brightness_update = led_update_flash_brightness,
> +	.indicator_brightness_set = led_set_indicator_brightness,
> +	.indicator_brightness_update = led_update_indicator_brightness,
> +	.strobe_set = led_set_flash_strobe,
> +	.strobe_get = led_get_flash_strobe,
> +	.timeout_set = led_set_flash_timeout,
> +	.external_strobe_set = led_set_external_strobe,
> +	.fault_get = led_get_flash_fault,
> +	.sysfs_lock = led_sysfs_lock,
> +	.sysfs_unlock = led_sysfs_unlock,
> +};
> +#define V4L2_FLASH_OPS (&v4l2_flash_ops)
> +#else
> +#define V4L2_FLASH_OPS NULL
> +#endif
> +
> +
> +void led_flash_remove_sysfs_groups(struct led_classdev *led_cdev)
> +{
> +	struct led_flash *flash = led_cdev->flash;
> +	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]);
> +}
> +
> +int led_flash_create_sysfs_groups(struct led_classdev *led_cdev)
> +{
> +	struct led_flash *flash = led_cdev->flash;
> +	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_group);
> +	if (ret < 0)
> +		goto err_create_group;
> +	flash->sysfs_groups[num_sysfs_groups++] = &led_flash_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 (flash->has_external_strobe) {
> +		ret = sysfs_create_group(&led_cdev->dev->kobj,
> +					&led_flash_external_strobe_group);
> +		if (ret < 0)
> +			goto err_create_group;
> +		flash->sysfs_groups[num_sysfs_groups++] =
> +					&led_flash_external_strobe_group;
> +	}
> +
> +	return 0;
> +
> +err_create_group:
> +	led_flash_remove_sysfs_groups(led_cdev);
> +	return ret;
> +}
> +
> +int led_classdev_flash_register(struct device *parent,
> +				struct led_classdev *led_cdev)
> +{
> +	struct led_flash *flash = led_cdev->flash;
> +	const struct led_flash_ops *ops;
> +	int ret;
> +
> +	if (!flash)
> +		return -EINVAL;
> +
> +	/* Register led class device */
> +	ret = led_classdev_register(parent, led_cdev);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (!flash->has_flash_led)
> +		goto exit;
> +
> +	/* Validate flash related ops */
> +	ops = &flash->ops;
> +	if (!ops || !ops->brightness_set || !ops->strobe_set || !ops->strobe_get
> +		|| !ops->timeout_set || !ops->fault_get)

Could you align the condition to right of the opening parenthese?

The adp1653 cannot tell the strobe status. While the driver is there I think
it's unlikely it'd ever be supported using the LED framework, I think making
strobe_get() optional now isn't necessary. Just FYI; things like this are
out there.

> +		return -EINVAL;
> +
> +	if (flash->has_external_strobe && !ops->external_strobe_set)
> +		return -EINVAL;
> +
> +	if (flash->indicator_brightness && !ops->indicator_brightness_set)
> +		return -EINVAL;
> +
> +	/* Install resume callback for flash controls */
> +	led_cdev->flash_resume = led_flash_resume;
> +
> +	/* Create flash led specific sysfs attributes */
> +	ret = led_flash_create_sysfs_groups(led_cdev);
> +	if (ret < 0)
> +		goto err_create_groups;
> +
> +exit:
> +	/* This will create V4L2 Flash sub-device if it is enabled */
> +	ret = v4l2_flash_init(led_cdev, V4L2_FLASH_OPS);

v4l2_flash_init() is only defined in the last patch. I think you need to
split it at least into two so you can have definitions for the LED class
patches that need them.

I think you could also refer to v4l2_flash_ops() directly, and make
v4l2_flash_init() a macro returning zero if CONFIG_V4L2_FLASH isn't defined.
As as result, you wouldn't need to define V4L2_FLASH_OPS.

On the naming of the config option --- as this is directly related to LED
class, what would you think about calling it CONFIG_V4L2_LED_CLASS or
CONFIG_V4L2_FLASH_LED_CLASS, for instance? The same API (but probably not
the implementation) supports also xenon flash devices.

> +	if (ret < 0)
> +		goto err_create_groups;

What about the sysfs groups?

> +
> +	return 0;
> +
> +err_create_groups:
> +	led_classdev_unregister(led_cdev);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(led_classdev_flash_register);
> +
> +void led_classdev_flash_unregister(struct led_classdev *led_cdev)
> +{
> +	v4l2_flash_release(led_cdev);
> +	led_flash_remove_sysfs_groups(led_cdev);
> +	led_classdev_unregister(led_cdev);
> +}
> +EXPORT_SYMBOL_GPL(led_classdev_flash_unregister);
> +
> +/* Caller must ensure led_cdev->led_lock held */
> +void led_sysfs_lock(struct led_classdev *led_cdev)
> +{

How about e.g. WARN_ON(!mutex_is_locked(&led_cdev->led_lock));?

> +	led_cdev->flags |= LED_SYSFS_LOCK;
> +}
> +EXPORT_SYMBOL(led_sysfs_lock);
> +
> +/* Caller must ensure led_cdev->led_lock held */
> +void led_sysfs_unlock(struct led_classdev *led_cdev)
> +{
> +	led_cdev->flags &= ~LED_SYSFS_LOCK;
> +}
> +EXPORT_SYMBOL(led_sysfs_unlock);
> +
> +int led_set_flash_strobe(struct led_classdev *led_cdev, bool state)
> +{
> +	if (!has_flash_op(strobe_set))
> +		return -EINVAL;
> +
> +	return call_flash_op(strobe_set, led_cdev, state);
> +}
> +EXPORT_SYMBOL(led_set_flash_strobe);
> +
> +int led_get_flash_strobe(struct led_classdev *led_cdev)
> +{
> +	if (!has_flash_op(strobe_get))
> +		return -EINVAL;
> +
> +	return call_flash_op(strobe_get, led_cdev);
> +}
> +EXPORT_SYMBOL(led_get_flash_strobe);
> +
> +void led_clamp_align_val(struct led_ctrl *c)
> +{
> +	u32 v, offset;
> +
> +	v = c->val + c->step / 2;
> +	v = clamp(v, c->min, c->max);
> +	offset = v - c->min;
> +	offset = c->step * (offset / c->step);
> +	c->val = c->min + offset;
> +}
> +
> +int led_set_flash_timeout(struct led_classdev *led_cdev, u32 timeout)
> +{
> +	struct led_flash *flash = led_cdev->flash;
> +	struct led_ctrl *c = &flash->timeout;
> +	int ret = 0;
> +
> +	if (!has_flash_op(timeout_set))
> +		return -EINVAL;
> +
> +	c->val = timeout;
> +	led_clamp_align_val(c);
> +
> +	if (!(led_cdev->flags & LED_SUSPENDED))
> +		ret = call_flash_op(timeout_set, led_cdev, c->val);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(led_set_flash_timeout);
> +
> +int led_get_flash_fault(struct led_classdev *led_cdev, u32 *fault)
> +{
> +	if (!has_flash_op(fault_get))
> +		return -EINVAL;
> +
> +	return call_flash_op(fault_get, led_cdev, fault);
> +}
> +EXPORT_SYMBOL(led_get_flash_fault);
> +
> +int led_set_external_strobe(struct led_classdev *led_cdev, bool enable)
> +{
> +	struct led_flash *flash = led_cdev->flash;
> +	int ret;
> +
> +	if (!has_flash_op(external_strobe_set))
> +		return -EINVAL;
> +
> +	if (flash->has_external_strobe) {
> +		ret = call_flash_op(external_strobe_set, led_cdev, enable);
> +		if (ret < 0)
> +			return -EINVAL;
> +		flash->external_strobe = enable;
> +	} else if (enable)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(led_set_external_strobe);
> +
> +int led_set_flash_brightness(struct led_classdev *led_cdev,
> +				u32 brightness)
> +{
> +	struct led_flash *flash = led_cdev->flash;
> +	struct led_ctrl *c = &flash->brightness;
> +	int ret = 0;
> +
> +	if (!has_flash_op(brightness_set))
> +		return -EINVAL;
> +
> +	c->val = brightness;
> +	led_clamp_align_val(c);
> +
> +	if (!(led_cdev->flags & LED_SUSPENDED))
> +		ret = call_flash_op(brightness_set, led_cdev, c->val);
> +	return ret;
> +}
> +EXPORT_SYMBOL(led_set_flash_brightness);
> +
> +int led_update_flash_brightness(struct led_classdev *led_cdev)
> +{
> +	struct led_flash *flash = led_cdev->flash;
> +	struct led_ctrl *c = &flash->brightness;
> +	u32 brightness;
> +	int ret = 0;
> +
> +	if (has_flash_op(brightness_get)) {
> +		ret = call_flash_op(brightness_get, led_cdev, &brightness);
> +		if (ret < 0)
> +			return ret;
> +		c->val = brightness;
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(led_update_flash_brightness);
> +
> +int led_set_indicator_brightness(struct led_classdev *led_cdev,
> +					u32 brightness)
> +{
> +	struct led_flash *flash = led_cdev->flash;
> +	struct led_ctrl *c = flash->indicator_brightness;
> +	int ret = 0;
> +
> +	if (!has_flash_op(indicator_brightness_set))
> +		return -EINVAL;
> +
> +	c->val = brightness;
> +	led_clamp_align_val(c);
> +
> +	if (!(led_cdev->flags & LED_SUSPENDED))
> +		ret = call_flash_op(indicator_brightness_set, led_cdev, c->val);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(led_set_indicator_brightness);
> +
> +int led_update_indicator_brightness(struct led_classdev *led_cdev)
> +{
> +	struct led_flash *flash = led_cdev->flash;
> +	struct led_ctrl *c = flash->indicator_brightness;
> +	u32 brightness;
> +	int ret = 0;
> +
> +	if (has_flash_op(indicator_brightness_get)) {
> +		ret = call_flash_op(indicator_brightness_get, led_cdev,
> +							&brightness);
> +		if (ret < 0)
> +			return ret;
> +		c->val = brightness;
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(led_update_indicator_brightness);
> +
> +static int __init leds_flash_init(void)
> +{
> +	return 0;
> +}
> +
> +static void __exit leds_flash_exit(void)
> +{
> +}
> +
> +subsys_initcall(leds_flash_init);
> +module_exit(leds_flash_exit);
> +
> +MODULE_AUTHOR("Jacek Anaszewski <j.anaszewski@xxxxxxxxxxx>");
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("LED Class Flash Interface");
> diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
> index df1a7c1..40e21c0 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_lock);
> +
> +	if (led_sysfs_is_locked(led_cdev)) {
> +		ret = -EBUSY;
> +		goto exit_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 exit_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 exit_unlock;
>  		}
>  	}
>  	up_read(&triggers_list_lock);
>  
> -	return -EINVAL;
> +exit_unlock:
> +	mutex_unlock(&led_cdev->led_lock);
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(led_trigger_store);
>  
> diff --git a/drivers/leds/leds.h b/drivers/leds/leds.h
> index 4c50365..f66a0c3 100644
> --- a/drivers/leds/leds.h
> +++ b/drivers/leds/leds.h
> @@ -17,6 +17,12 @@
>  #include <linux/rwsem.h>
>  #include <linux/leds.h>
>  
> +#define call_flash_op(op, args...)		\
> +	((led_cdev)->flash->ops.op(args))
> +
> +#define has_flash_op(op)			\
> +	((led_cdev)->flash && (led_cdev)->flash->ops.op)

I think you're using the two in a pattern where you first check if the op is
there, and then call it if it is. Could you combine both into
call_flash_op(), and return an error if the op isn't there?

>  static inline void __led_set_brightness(struct led_classdev *led_cdev,
>  					enum led_brightness value)
>  {
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 0287ab2..a794817 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -13,12 +13,14 @@
>  #define __LINUX_LEDS_H_INCLUDED
>  
>  #include <linux/list.h>
> -#include <linux/spinlock.h>
> +#include <linux/mutex.h>
>  #include <linux/rwsem.h>
> +#include <linux/spinlock.h>
>  #include <linux/timer.h>
>  #include <linux/workqueue.h>
>  
>  struct device;
> +struct led_flash;
>  /*
>   * LED Core
>   */
> @@ -29,6 +31,28 @@ enum led_brightness {
>  	LED_FULL	= 255,
>  };
>  
> +/*
> + * This structure is required in two cases:
> + * - it defines allowed levels of flash leds brightness and timeout
> + * - it provides initialization data for V4L2 Flash controls
> + *   when CONFIG_V4L2_FLASH is enabled and allows for proper
> + *   enum led_brightness <-> microamperes conversion for the
> + *   V4L2_CID_FLASH_TORCH_INTENSITY
> + */
> +struct led_ctrl {
> +	/* maximum allowed value */
> +	u32 min;
> +	/* maximum allowed value */
> +	u32 max;
> +	/* step value */
> +	u32 step;
> +	/*
> +	 * Default value for V4L2 controls and for flash leds
> +	 * it also serves for caching the value currently set.
> +	 */
> +	u32 val;
> +};
> +
>  struct led_classdev {
>  	const char		*name;
>  	int			 brightness;
> @@ -42,6 +66,7 @@ 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_LOCK		(1 << 21)
>  
>  	/* Set LED brightness level */
>  	/* Must not sleep, use a workqueue if needed */
> @@ -69,6 +94,17 @@ struct led_classdev {
>  	unsigned long		 blink_delay_on, blink_delay_off;
>  	struct timer_list	 blink_timer;
>  	int			 blink_brightness;
> +	struct led_flash	*flash;
> +	void			(*flash_resume)(struct led_classdev *led_cdev);
> +#ifdef CONFIG_V4L2_FLASH
> +	/* Initialization data for the V4L2_CID_FLASH_TORCH_INTENSITY control */
> +	struct led_ctrl		brightness_ctrl;
> +#endif
> +	/*
> +	 * Ensures consistent LED sysfs access and protects
> +	 * LED sysfs locking mechanism
> +	 */
> +	struct mutex		led_lock;
>  
>  	struct work_struct	set_brightness_work;
>  	int			delayed_set_value;
> @@ -139,6 +175,18 @@ extern void led_blink_set_oneshot(struct led_classdev *led_cdev,
>  extern void led_set_brightness(struct led_classdev *led_cdev,
>  			       enum led_brightness brightness);
>  
> +/**
> + * led_sysfs_is_locked
> + * @led_cdev: the LED to query
> + *
> + * Returns: true if the sysfs interface of the led is disabled,
> + *	    false otherwise
> + */
> +static inline bool led_sysfs_is_locked(struct led_classdev *led_cdev)
> +{
> +	return led_cdev->flags & LED_SYSFS_LOCK;
> +}
> +
>  /*
>   * LED Triggers
>   */
> diff --git a/include/linux/leds_flash.h b/include/linux/leds_flash.h
> new file mode 100644
> index 0000000..0f885a0
> --- /dev/null
> +++ b/include/linux/leds_flash.h
> @@ -0,0 +1,252 @@
> +/*
> + * Flash leds API
> + *
> + * Copyright (C) 2014 Samsung Electronics Co., Ltd.
> + * Author: Jacek Anaszewski <j.anaszewski@xxxxxxxxxxx>
> + *
> + * 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 <media/v4l2-flash.h>
> +#include <linux/leds.h>

"l" comes before "m".

> +/*
> + * Supported led fault bits - must be kept in synch
> + * with V4L2_FLASH_FAULT bits.
> + */
> +#define LED_FAULT_OVER_VOLTAGE		(1 << 0)
> +#define LED_FAULT_TIMEOUT		(1 << 1)
> +#define LED_FAULT_OVER_TEMPERATURE	(1 << 2)
> +#define LED_FAULT_SHORT_CIRCUIT		(1 << 3)
> +#define LED_FAULT_OVER_CURRENT		(1 << 4)
> +#define LED_FAULT_INDICATOR		(1 << 5)
> +#define LED_FAULT_UNDER_VOLTAGE		(1 << 6)
> +#define LED_FAULT_INPUT_VOLTAGE		(1 << 7)
> +#define LED_FAULT_LED_OVER_TEMPERATURE	(1 << 8)
> +
> +#define LED_FLASH_MAX_SYSFS_GROUPS 3
> +
> +struct led_flash_ops {
> +	/* set flash brightness */
> +	int	(*brightness_set)(struct led_classdev *led_cdev,
> +					u32 brightness);
> +	/* get flash brightness */
> +	int (*brightness_get)(struct led_classdev *led_cdev, u32 *brightness);
> +	/* set flash indicator brightness */
> +	int	(*indicator_brightness_set)(struct led_classdev *led_cdev,
> +					u32 brightness);
> +	/* get flash indicator brightness */
> +	int (*indicator_brightness_get)(struct led_classdev *led_cdev,
> +					u32 *brightness);
> +	/* setup flash strobe */
> +	int	(*strobe_set)(struct led_classdev *led_cdev,
> +					bool state);
> +	/* get flash strobe state */
> +	int	(*strobe_get)(struct led_classdev *led_cdev);
> +	/* setup flash timeout */
> +	int	(*timeout_set)(struct led_classdev *led_cdev,
> +					u32 timeout);

Fits on a single line. Applies to some others as well.

> +	/* setup strobing the flash from external source */
> +	int	(*external_strobe_set)(struct led_classdev *led_cdev,
> +					bool enable);
> +	/* get the flash LED fault */
> +	int	(*fault_get)(struct led_classdev *led_cdev,
> +					u32 *fault);
> +};
> +
> +struct led_flash {
> +	/*
> +	 * 1 - add support for both flash and torch leds,
> +	 * 0 - handle only torch led
> +	 */
> +	bool		has_flash_led;
> +	/* 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_ctrl brightness;
> +
> +	/* timeout value in microseconds along with its constraints */
> +	struct led_ctrl timeout;
> +
> +	/*
> +	 * Indicator brightness value in microamperes along with
> +	 * its constraints - this is an optional control and must
> +	 * be allocated by the driver if the device supports privacy
> +	 * indicator led.
> +	 */
> +	struct led_ctrl *indicator_brightness;
> +
> +	/*
> +	 * determines whether device supports external
> +	 * flash strobe sources
> +	 */
> +	bool		has_external_strobe;
> +
> +	/*
> +	 * If true the device doesn't strobe the flash immediately
> +	 * after writing 1 to the flash_strobe file, but waits
> +	 * for an external signal.
> +	 */
> +	bool		external_strobe;
> +
> +#ifdef CONFIG_V4L2_FLASH
> +	/* V4L2 Flash sub-device data */
> +	struct		v4l2_flash v4l2_flash;
> +
> +	/* flash fault bits that may be set by the device */
> +	u32 fault_flags;
> +#endif
> +
> +};
> +
> +/**
> + * led_classdev_flash_register - register a new object of led_classdev class
> +				 with support for flash LEDs
> + * @parent: the device to register
> + * @led_cdev: the led_classdev structure for this device
> + *
> + * Returns: 0 on success, error code on failure.
> + */
> +int led_classdev_flash_register(struct device *parent,
> +				struct led_classdev *led_cdev);
> +
> +/**
> + * led_classdev_flash_unregister - unregisters an object of led_properties class
> +				 with support for flash LEDs
> + * @led_cdev: the flash led device to unregister
> + *
> + * Unregisters a previously registered via led_classdev_flash_register object
> + */
> +void led_classdev_flash_unregister(struct led_classdev *led_cdev);
> +
> +/**
> + * led_set_flash_strobe - setup flash strobe
> + * @led_cdev: 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 *led_cdev, bool state);
> +
> +/**
> + * led_get_flash_strobe - get flash strobe status
> + * @led_cdev: the LED to query
> + *
> + * Check whether the flash is strobing at the moment or not.
> + *
> + * Returns: flash strobe status (0 or 1) on success or negative
> + *	    error value on failure.
> + */
> +extern int led_get_flash_strobe(struct led_classdev *led_cdev);
> +
> +/**
> + * led_set_flash_brightness - set flash LED brightness
> + * @led_cdev: the LED to set
> + * @brightness: the brightness to set it to
> + *
> + * Returns: 0 on success, -EINVAL on failure

Could this function return other error codes? Same for other functions
below where a specific error code is listed.

> + * Set a flash LED's brightness.
> + */
> +extern int led_set_flash_brightness(struct led_classdev *led_cdev,
> +					u32 brightness);
> +
> +/**
> + * led_update_flash_brightness - update flash LED brightness
> + * @led_cdev: the 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 *led_cdev);
> +
> +/**
> + * led_set_flash_timeout - set flash LED timeout
> + * @led_cdev: the LED to set
> + * @timeout: the flash timeout to set it to
> + *
> + * Returns: 0 on success, -EINVAL on failure
> + *
> + * 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.
> + */
> +extern int led_set_flash_timeout(struct led_classdev *led_cdev,
> +					u32 timeout);
> +
> +/**
> + * led_get_flash_fault - get the flash LED fault
> + * @led_cdev: the LED to query
> + * @fault: bitmask containing flash faults
> + *
> + * Returns: 0 on success, -EINVAL on failure
> + *
> + * Get the flash LED fault.
> + */
> +extern int led_get_flash_fault(struct led_classdev *led_cdev,
> +					u32 *fault);
> +
> +/**
> + * led_set_external_strobe - set the flash LED external_strobe mode
> + * @led_cdev: the LED to set
> + * @enable: the state to set it to
> + *
> + * Returns: 0 on success, -EINVAL on failure
> + *
> + * Enable/disable strobing the flash LED with use of external source
> + */
> +extern int led_set_external_strobe(struct led_classdev *led_cdev, bool enable);
> +
> +/**
> + * led_set_indicator_brightness - set indicator LED brightness
> + * @led_cdev: the LED to set
> + * @brightness: the brightness to set it to
> + *
> + * Returns: 0 on success, -EINVAL on failure
> + *
> + * Set a flash LED's brightness.
> + */
> +extern int led_set_indicator_brightness(struct led_classdev *led_cdev,
> +					u32 led_brightness);
> +
> +/**
> + * led_update_indicator_brightness - update flash indicator LED brightness
> + * @led_cdev: the 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 *led_cdev);
> +
> +/**
> + * led_sysfs_lock - lock LED sysfs interface
> + * @led_cdev: the LED to set
> + *
> + * Lock the LED's sysfs interface
> + */
> +extern void led_sysfs_lock(struct led_classdev *led_cdev);
> +
> +/**
> + * led_sysfs_unlock - unlock LED sysfs interface
> + * @led_cdev: the LED to set
> + *
> + * Unlock the LED's sysfs interface
> + */
> +extern void led_sysfs_unlock(struct led_classdev *led_cdev);
> +
> +#endif	/* __LINUX_FLASH_LEDS_H_INCLUDED */

-- 
Kind regards,

Sakari Ailus
e-mail: sakari.ailus@xxxxxx	XMPP: sailus@xxxxxxxxxxxxxx
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