libata: implement dump_id force param

[safe/jmp/linux-2.6] / Documentation / leds-class.txt

diff --git a/Documentation/leds-class.txt b/Documentation/leds-class.txt
index 8c35c04..8fd5ca2 100644 (file)
--- a/Documentation/leds-class.txt
+++ b/Documentation/leds-class.txt
@@ -1,3 +1,4 @@
+

 LED handling under Linux
 ========================
 
 LED handling under Linux
 ========================
 


@@ -5,10 +6,10 @@ If you're reading this and thinking about keyboard leds, these are
 handled by the input subsystem and the led class is *not* needed.
 
 In its simplest form, the LED class just allows control of LEDs from
 handled by the input subsystem and the led class is *not* needed.
 
 In its simplest form, the LED class just allows control of LEDs from

-userspace. LEDs appear in /sys/class/leds/. The brightness file will
-set the brightness of the LED (taking a value 0-255). Most LEDs don't
-have hardware brightness support so will just be turned on for non-zero
-brightness settings.
+userspace. LEDs appear in /sys/class/leds/. The maximum brightness of the
+LED is defined in max_brightness file. The brightness file will set the brightness
+of the LED (taking a value 0-max_brightness). Most LEDs don't have hardware
+brightness support so will just be turned on for non-zero brightness settings.

 
 The class also introduces the optional concept of an LED trigger. A trigger
 is a kernel based source of led events. Triggers can either be simple or
 
 The class also introduces the optional concept of an LED trigger. A trigger
 is a kernel based source of led events. Triggers can either be simple or


@@ -19,6 +20,12 @@ 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 +46,33 @@ 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 +83,6 @@ 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
 ==================