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Diffstat (limited to 'Documentation/leds-class.txt')
| -rw-r--r-- | Documentation/leds-class.txt | 29 |
1 files changed, 23 insertions, 6 deletions
diff --git a/Documentation/leds-class.txt b/Documentation/leds-class.txt index 8c35c042611..56757c751d6 100644 --- a/Documentation/leds-class.txt +++ b/Documentation/leds-class.txt @@ -39,12 +39,33 @@ LED Device Naming Is currently of the form: -"devicename:colour" +"devicename:colour:function" There have been calls for LED properties such as colour to be exported as individual led class attributes. As a solution which doesn't incur as much overhead, I suggest these become part of the device name. The naming scheme -above leaves scope for further attributes should they be needed. +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 @@ -55,10 +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 ================== |