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| author | Márton Németh <nm127@freemail.hu> | 2007-10-31 15:07:12 +0100 |
|---|---|---|
| committer | Richard Purdie <rpurdie@rpsys.net> | 2008-02-07 09:49:38 +0000 |
| commit | 4c79141d28bc290ae307e3f81f5bc909c26faf6e (patch) | |
| tree | 9c6dc51c441dfc1c84cc27ece43087515c06967c /Documentation | |
| parent | 6c152beefbf90579d21afc4f7e075b1f801f9a75 (diff) | |
| download | linux-3.10-4c79141d28bc290ae307e3f81f5bc909c26faf6e.tar.gz linux-3.10-4c79141d28bc290ae307e3f81f5bc909c26faf6e.tar.bz2 linux-3.10-4c79141d28bc290ae307e3f81f5bc909c26faf6e.zip | |
leds: Add support for hardware accelerated LED flashing
Extends the leds subsystem with a blink_set() callback function which can
be optionally implemented by a LED driver. If implemented, the driver can use
the hardware acceleration for blinking a LED.
Signed-off-by: Márton Németh <nm127@freemail.hu>
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/leds-class.txt | 24 |
1 files changed, 20 insertions, 4 deletions
diff --git a/Documentation/leds-class.txt b/Documentation/leds-class.txt index 877af6efc18..56757c751d6 100644 --- a/Documentation/leds-class.txt +++ b/Documentation/leds-class.txt @@ -48,6 +48,26 @@ above leaves scope for further attributes should they be needed. If sections of the name don't apply, just leave that section blank. +Hardware accelerated blink of LEDs +================================== + +Some LEDs can be programmed to blink without any CPU interaction. To +support this feature, a LED driver can optionally implement the +blink_set() function (see <linux/leds.h>). If implemeted, triggers can +attempt to use it before falling back to software timers. The blink_set() +function should return 0 if the blink setting is supported, or -EINVAL +otherwise, which means that LED blinking will be handled by software. + +The blink_set() function should choose a user friendly blinking +value if it is called with *delay_on==0 && *delay_off==0 parameters. In +this case the driver should give back the chosen value through delay_on +and delay_off parameters to the leds subsystem. + +Any call to the brightness_set() callback function should cancel the +previously programmed hardware blinking function so setting the brightness +to 0 can also cancel the blinking of the LED. + + Known Issues ============ @@ -56,10 +76,6 @@ would cause nightmare dependency issues. I see this as a minor issue compared to the benefits the simple trigger functionality brings. The rest of the LED subsystem can be modular. -Some leds can be programmed to flash in hardware. As this isn't a generic -LED device property, this should be exported as a device specific sysfs -attribute rather than part of the class if this functionality is required. - Future Development ================== |