Jacek
On 10/2/19 12:46 PM, Jacek Anaszewski wrote:
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 <gre...@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <raf...@kernel.org>
Cc: Jacek Anaszewski <jacek.anaszew...@gmail.com>
Cc: Pavel Machek <pa...@ucw.cz>
Cc: Dan Murphy <dmur...@ti.com>
Signed-off-by: Akinobu Mita <akinobu.m...@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-l...@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.
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.
So if it has been in place for a very long time why do we need another
ABI that does sorta the same thing?
This seems to be a bit confusing and extra.
Maybe this ABI should be RO where a user can read the current-trigger as
a single value per file but writing the trigger still
is done through the old ABI.
Dan
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
