[ARM] Feroceon: small cleanups to L2 cache code

[linux-2.6-omap-h63xx.git] / Documentation / leds-class.txt

diff --git a/Documentation/leds-class.txt b/Documentation/leds-class.txt
index 8c35c0426110f149100be9cb2c17921e8e25ae39..6399557cdab3d6542a0feea0c0cd2c6b2af5ffad 100644 (file)
--- a/Documentation/leds-class.txt
+++ b/Documentation/leds-class.txt
@@ -19,6 +19,12 @@ optimises away.
 
 Complex triggers whilst available to all LEDs have LED specific
 parameters and work on a per LED basis. The timer trigger is an example.
 
 Complex triggers whilst available to all LEDs have LED specific
 parameters and work on a per LED basis. The timer trigger is an example.

+The timer trigger will periodically change the LED brightness between
+LED_OFF and the current brightness setting. The "on" and "off" time can
+be specified via /sys/class/leds/<device>/delay_{on,off} in milliseconds.
+You can change the brightness value of a LED independently of the timer
+trigger. However, if you set the brightness value to LED_OFF it will
+also disable the timer trigger.

 
 You can change triggers in a similar manner to the way an IO scheduler
 is chosen (via /sys/class/leds/<device>/trigger). Trigger specific
 
 You can change triggers in a similar manner to the way an IO scheduler
 is chosen (via /sys/class/leds/<device>/trigger). Trigger specific


@@ -39,12 +45,33 @@ LED Device Naming
 
 Is currently of the form:
 
 
 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
 
 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 implemented, 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.
+
+Setting the brightness to zero with brightness_set() callback function
+should completely turn off the LED and cancel the previously programmed
+hardware blinking function, if any.

 
 
 Known Issues
 
 
 Known Issues


@@ -55,10 +82,6 @@ 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.
 
 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
 ==================
 
 Future Development
 ==================