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SubjectRe: [PATCH -next 2/2] leds: add /sys/class/leds/<led>/current-trigger
On Thu, Oct 03, 2019 at 12:13:01AM +0900, Akinobu Mita wrote:
> Reading /sys/class/leds/<led>/trigger returns all available LED triggers.
> However, this violates the "one value per file" rule of sysfs.
>
> This provides /sys/class/leds/<led>/current-trigger which is almost
> identical to /sys/class/leds/<led>/trigger. The only difference is that
> 'current-trigger' only shows the current trigger name.
>
> This new file follows the "one value per file" rule of sysfs.
> We can find all available LED triggers by listing the
> /sys/devices/virtual/led-trigger/ directory.
>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>
> Cc: Pavel Machek <pavel@ucw.cz>
> Cc: Dan Murphy <dmurphy@ti.com>
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> ---
> Documentation/ABI/testing/sysfs-class-led | 13 +++++++++++
> drivers/leds/led-class.c | 10 ++++++++
> drivers/leds/led-triggers.c | 38 +++++++++++++++++++++++++++----
> drivers/leds/leds.h | 5 ++++
> 4 files changed, 62 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led
> index 5f67f7a..fdfed3f 100644
> --- a/Documentation/ABI/testing/sysfs-class-led
> +++ b/Documentation/ABI/testing/sysfs-class-led
> @@ -61,3 +61,16 @@ Description:
> gpio and backlight triggers. In case of the backlight trigger,
> it is useful when driving a LED which is intended to indicate
> a device in a standby like state.
> +
> +What: /sys/class/leds/<led>/current-trigger
> +Date: September 2019
> +KernelVersion: 5.5
> +Contact: linux-leds@vger.kernel.org
> +Description:
> + Set the trigger for this LED. A trigger is a kernel based source
> + of LED events.
> + Writing the trigger name to this file will change the current
> + trigger. Trigger specific parameters can appear in
> + /sys/class/leds/<led> once a given trigger is selected. For
> + their documentation see sysfs-class-led-trigger-*.
> + Reading this file will return the current LED trigger name.
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index 3f04334..3cb0d8a 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -74,12 +74,22 @@ static ssize_t max_brightness_show(struct device *dev,
> static DEVICE_ATTR_RO(max_brightness);
>
> #ifdef CONFIG_LEDS_TRIGGERS
> +
> +static DEVICE_ATTR(current_trigger, 0644, led_current_trigger_show,
> + led_current_trigger_store);

DEVICE_ATTR_RW() please.

> +static struct attribute *led_current_trigger_attrs[] = {
> + &dev_attr_current_trigger.attr,
> + NULL,
> +};
> +
> static BIN_ATTR(trigger, 0644, led_trigger_read, led_trigger_write, 0);
> static struct bin_attribute *led_trigger_bin_attrs[] = {
> &bin_attr_trigger,
> NULL,
> };
> static const struct attribute_group led_trigger_group = {
> + .attrs = led_current_trigger_attrs,
> .bin_attrs = led_trigger_bin_attrs,
> };
> #endif
> diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
> index 0b810cf..a2ef674 100644
> --- a/drivers/leds/led-triggers.c
> +++ b/drivers/leds/led-triggers.c
> @@ -27,11 +27,9 @@ LIST_HEAD(trigger_list);
>
> /* Used by LED Class */
>
> -ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,
> - struct bin_attribute *bin_attr, char *buf,
> - loff_t pos, size_t count)
> +static ssize_t led_trigger_store(struct device *dev, const char *buf,
> + size_t count)
> {
> - struct device *dev = kobj_to_dev(kobj);
> struct led_classdev *led_cdev = dev_get_drvdata(dev);
> struct led_trigger *trig;
> int ret = count;
> @@ -67,8 +65,25 @@ ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,
> mutex_unlock(&led_cdev->led_access);
> return ret;
> }
> +
> +ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,
> + struct bin_attribute *bin_attr, char *buf,
> + loff_t pos, size_t count)
> +{
> + struct device *dev = kobj_to_dev(kobj);
> +
> + return led_trigger_store(dev, buf, count);
> +}
> EXPORT_SYMBOL_GPL(led_trigger_write);
>
> +ssize_t led_current_trigger_store(struct device *dev,
> + struct device_attribute *attr, const char *buf,
> + size_t count)
> +{
> + return led_trigger_store(dev, buf, count);
> +}
> +EXPORT_SYMBOL_GPL(led_current_trigger_store);
> +
> __printf(3, 4)
> static int led_trigger_snprintf(char *buf, ssize_t size, const char *fmt, ...)
> {
> @@ -144,6 +159,21 @@ ssize_t led_trigger_read(struct file *filp, struct kobject *kobj,
> }
> EXPORT_SYMBOL_GPL(led_trigger_read);
>
> +ssize_t led_current_trigger_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct led_classdev *led_cdev = dev_get_drvdata(dev);
> + int len;
> +
> + down_read(&led_cdev->trigger_lock);
> + len = scnprintf(buf, PAGE_SIZE, "%s\n", led_cdev->trigger ?

No need for "scnprintf() when writing a single number to a buffer. Just
use sprintf() please.

> + led_cdev->trigger->name : "none");

Can you have a trigger named "none"? :)

thanks,

greg k-h

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