sh: convert /proc/cpu/aligmnent, /proc/cpu/kernel_alignment to seq_file

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

diff --git a/Documentation/leds-class.txt b/Documentation/leds-class.txt
index 56757c7..8fd5ca2 100644 (file)
--- a/Documentation/leds-class.txt
+++ b/Documentation/leds-class.txt
@@ -1,3 +1,4 @@
+
 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
-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
@@ -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.
+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
@@ -53,7 +60,7 @@ 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
+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.
@@ -63,9 +70,9 @@ 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.
+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