Linux Headquarters
[ Register ]
[ About us ] [ Home Page ]

[ Kernel ] [ Documentation ] [ Links ] [ Books ]

Kernel v2.6.25-rc7 /Documentation/leds-class.txt

Filename:/Documentation/leds-class.txt
Lines Added:23
Lines Deleted:6
Also changed in: (Previous) 2.6.25-rc6  2.6.25-rc5  2.6.25-rc4  2.6.25-rc3  2.6.25-rc2  2.6.25-rc1 
(Following) 2.6.25-rc8  2.6.25-rc9  2.6.25  2.6.25-git8  2.6.25-git9  2.6.25-git10 

Location
[  2.6.25-rc7
  [  Documentation
     o  leds-class.txt

Patch

diff --git a/Documentation/leds-class.txt b/Documentation/leds-class.txt
index 8c35c04..56757c7 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
 ==================


Comments: webmaster (at) linuxhq.com.
Advertising: banners (at) linuxhq.com.
Compilation ©1998-2008 Linux Headquarters, Inc.