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authorLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-07 09:45:14 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-07 09:45:14 -0800
commit3d50337f62a61027f40ad4ceddefa3c91e5d479e (patch)
treec89bed784ab0fc402e9f4155f500170c9a335949 /Documentation
parent5b808a593588b2e6235c59fcd278791c53667787 (diff)
parentd39a7a63eb3971b1b3cc5c181ed526bf437b1c72 (diff)
Merge branch 'for-linus' of git://git.o-hand.com/linux-rpurdie-leds
* 'for-linus' of git://git.o-hand.com/linux-rpurdie-leds: leds: Add HP Jornada 6xx driver leds: Remove the now uneeded ixp4xx driver leds: Add power LED to the wrap driver leds: Fix led-gpio active_low default brightness leds: hw acceleration for Clevo mail LED driver leds: Add support for hardware accelerated LED flashing leds: Standardise LED naming scheme leds: Add clevo notebook LED driver
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/leds-class.txt29
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
==================