Dan, On 10/2/19 5:47 PM, Dan Murphy wrote: > Akinobu > > On 10/2/19 10:13 AM, 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@xxxxxxxxxxxxxxxxxxx> >> Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx> >> Cc: Jacek Anaszewski <jacek.anaszewski@xxxxxxxxx> >> Cc: Pavel Machek <pavel@xxxxxx> >> Cc: Dan Murphy <dmurphy@xxxxxx> >> Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx> >> --- >> 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@xxxxxxxxxxxxxxx >> +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. > > Why do we need this new file can't we just update the current trigger > file implementation? We can't change existing ABI. It doesn't matter if it is documented or not - it's in place for very long time and you can't guarantee there are no users relying on triggers file show format. > I don't see any documentation that states that the read of the trigger > file will print a list of known triggers. > > And writing to the trigger file still works so I would think the _show > just needs to be fixed. > > Besides this patch does not fix the issue in the commit message that the > trigger file still violates the one value per file rule. > > Dan > > -- Best regards, Jacek Anaszewski
