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authorLinus Torvalds <torvalds@linux-foundation.org>2009-09-23 20:32:11 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-23 20:32:11 +0400
commitc11f6c82581e8be4e1829c677db54e7f55cebece (patch)
tree1a116241b0831ded998aabe800bdc24104cbd826 /Documentation
parent40aba218969914d1b225e742617adb921cf94eae (diff)
parent193a6dec1c0246a80b6d0101e4f351ccf877bcac (diff)
downloadlinux-c11f6c82581e8be4e1829c677db54e7f55cebece.tar.xz
Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6
* 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6: (119 commits) ACPI: don't pass handle for fixed hardware notifications ACPI: remove null pointer checks in deferred execution path ACPI: simplify deferred execution path acerhdf: additional BIOS versions acerhdf: convert to dev_pm_ops acerhdf: fix fan control for AOA150 model thermal: add missing Kconfig dependency acpi: switch /proc/acpi/{debug_layer,debug_level} to seq_file hp-wmi: fix rfkill memory leak on unload ACPI: remove unnecessary #ifdef CONFIG_DMI ACPI: linux/acpi.h should not include linux/dmi.h hwmon driver for ACPI 4.0 power meters topstar-laptop: add new driver for hotkeys support on Topstar N01 thinkpad_acpi: fix rfkill memory leak on unload thinkpad-acpi: report brightness events when required thinkpad-acpi: don't poll by default any of the reserved hotkeys thinkpad-acpi: Fix procfs hotkey reset command thinkpad-acpi: deprecate hotkey_bios_mask thinkpad-acpi: hotkey poll fixes thinkpad-acpi: be more strict when detecting a ThinkPad ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ABI/stable/sysfs-class-backlight36
-rw-r--r--Documentation/ABI/testing/sysfs-class-lcd23
-rw-r--r--Documentation/ABI/testing/sysfs-class-led28
-rw-r--r--Documentation/ABI/testing/sysfs-platform-asus-laptop52
-rw-r--r--Documentation/ABI/testing/sysfs-platform-eeepc-laptop50
-rw-r--r--Documentation/hwmon/acpi_power_meter51
-rw-r--r--Documentation/laptops/asus-laptop.txt258
-rw-r--r--Documentation/laptops/thinkpad-acpi.txt8
-rw-r--r--Documentation/leds-class.txt9
9 files changed, 509 insertions, 6 deletions
diff --git a/Documentation/ABI/stable/sysfs-class-backlight b/Documentation/ABI/stable/sysfs-class-backlight
new file mode 100644
index 000000000000..4d637e1c4ff7
--- /dev/null
+++ b/Documentation/ABI/stable/sysfs-class-backlight
@@ -0,0 +1,36 @@
+What: /sys/class/backlight/<backlight>/bl_power
+Date: April 2005
+KernelVersion: 2.6.12
+Contact: Richard Purdie <rpurdie@rpsys.net>
+Description:
+ Control BACKLIGHT power, values are FB_BLANK_* from fb.h
+ - FB_BLANK_UNBLANK (0) : power on.
+ - FB_BLANK_POWERDOWN (4) : power off
+Users: HAL
+
+What: /sys/class/backlight/<backlight>/brightness
+Date: April 2005
+KernelVersion: 2.6.12
+Contact: Richard Purdie <rpurdie@rpsys.net>
+Description:
+ Control the brightness for this <backlight>. Values
+ are between 0 and max_brightness. This file will also
+ show the brightness level stored in the driver, which
+ may not be the actual brightness (see actual_brightness).
+Users: HAL
+
+What: /sys/class/backlight/<backlight>/actual_brightness
+Date: March 2006
+KernelVersion: 2.6.17
+Contact: Richard Purdie <rpurdie@rpsys.net>
+Description:
+ Show the actual brightness by querying the hardware.
+Users: HAL
+
+What: /sys/class/backlight/<backlight>/max_brightness
+Date: April 2005
+KernelVersion: 2.6.12
+Contact: Richard Purdie <rpurdie@rpsys.net>
+Description:
+ Maximum brightness for <backlight>.
+Users: HAL
diff --git a/Documentation/ABI/testing/sysfs-class-lcd b/Documentation/ABI/testing/sysfs-class-lcd
new file mode 100644
index 000000000000..35906bf7aa70
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-lcd
@@ -0,0 +1,23 @@
+What: /sys/class/lcd/<lcd>/lcd_power
+Date: April 2005
+KernelVersion: 2.6.12
+Contact: Richard Purdie <rpurdie@rpsys.net>
+Description:
+ Control LCD power, values are FB_BLANK_* from fb.h
+ - FB_BLANK_UNBLANK (0) : power on.
+ - FB_BLANK_POWERDOWN (4) : power off
+
+What: /sys/class/lcd/<lcd>/contrast
+Date: April 2005
+KernelVersion: 2.6.12
+Contact: Richard Purdie <rpurdie@rpsys.net>
+Description:
+ Current contrast of this LCD device. Value is between 0 and
+ /sys/class/lcd/<lcd>/max_contrast.
+
+What: /sys/class/lcd/<lcd>/max_contrast
+Date: April 2005
+KernelVersion: 2.6.12
+Contact: Richard Purdie <rpurdie@rpsys.net>
+Description:
+ Maximum contrast for this LCD device.
diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led
new file mode 100644
index 000000000000..9e4541d71cb6
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-led
@@ -0,0 +1,28 @@
+What: /sys/class/leds/<led>/brightness
+Date: March 2006
+KernelVersion: 2.6.17
+Contact: Richard Purdie <rpurdie@rpsys.net>
+Description:
+ Set the brightness of the LED. Most LEDs don't
+ have hardware brightness support so will just be turned on for
+ non-zero brightness settings. The value is between 0 and
+ /sys/class/leds/<led>/max_brightness.
+
+What: /sys/class/leds/<led>/max_brightness
+Date: March 2006
+KernelVersion: 2.6.17
+Contact: Richard Purdie <rpurdie@rpsys.net>
+Description:
+ Maximum brightness level for this led, default is 255 (LED_FULL).
+
+What: /sys/class/leds/<led>/trigger
+Date: March 2006
+KernelVersion: 2.6.17
+Contact: Richard Purdie <rpurdie@rpsys.net>
+Description:
+ Set the trigger for this LED. A trigger is a kernel based source
+ of led events.
+ You can change triggers in a similar manner to the way an IO
+ scheduler is chosen. Trigger specific parameters can appear in
+ /sys/class/leds/<led> once a given trigger is selected.
+
diff --git a/Documentation/ABI/testing/sysfs-platform-asus-laptop b/Documentation/ABI/testing/sysfs-platform-asus-laptop
new file mode 100644
index 000000000000..a1cb660c50cf
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-platform-asus-laptop
@@ -0,0 +1,52 @@
+What: /sys/devices/platform/asus-laptop/display
+Date: January 2007
+KernelVersion: 2.6.20
+Contact: "Corentin Chary" <corentincj@iksaif.net>
+Description:
+ This file allows display switching. The value
+ is composed by 4 bits and defined as follow:
+ 4321
+ |||`- LCD
+ ||`-- CRT
+ |`--- TV
+ `---- DVI
+ Ex: - 0 (0000b) means no display
+ - 3 (0011b) CRT+LCD.
+
+What: /sys/devices/platform/asus-laptop/gps
+Date: January 2007
+KernelVersion: 2.6.20
+Contact: "Corentin Chary" <corentincj@iksaif.net>
+Description:
+ Control the gps device. 1 means on, 0 means off.
+Users: Lapsus
+
+What: /sys/devices/platform/asus-laptop/ledd
+Date: January 2007
+KernelVersion: 2.6.20
+Contact: "Corentin Chary" <corentincj@iksaif.net>
+Description:
+ Some models like the W1N have a LED display that can be
+ used to display several informations.
+ To control the LED display, use the following :
+ echo 0x0T000DDD > /sys/devices/platform/asus-laptop/
+ where T control the 3 letters display, and DDD the 3 digits display.
+ The DDD table can be found in Documentation/laptops/asus-laptop.txt
+
+What: /sys/devices/platform/asus-laptop/bluetooth
+Date: January 2007
+KernelVersion: 2.6.20
+Contact: "Corentin Chary" <corentincj@iksaif.net>
+Description:
+ Control the bluetooth device. 1 means on, 0 means off.
+ This may control the led, the device or both.
+Users: Lapsus
+
+What: /sys/devices/platform/asus-laptop/wlan
+Date: January 2007
+KernelVersion: 2.6.20
+Contact: "Corentin Chary" <corentincj@iksaif.net>
+Description:
+ Control the bluetooth device. 1 means on, 0 means off.
+ This may control the led, the device or both.
+Users: Lapsus
diff --git a/Documentation/ABI/testing/sysfs-platform-eeepc-laptop b/Documentation/ABI/testing/sysfs-platform-eeepc-laptop
new file mode 100644
index 000000000000..7445dfb321b5
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-platform-eeepc-laptop
@@ -0,0 +1,50 @@
+What: /sys/devices/platform/eeepc-laptop/disp
+Date: May 2008
+KernelVersion: 2.6.26
+Contact: "Corentin Chary" <corentincj@iksaif.net>
+Description:
+ This file allows display switching.
+ - 1 = LCD
+ - 2 = CRT
+ - 3 = LCD+CRT
+ If you run X11, you should use xrandr instead.
+
+What: /sys/devices/platform/eeepc-laptop/camera
+Date: May 2008
+KernelVersion: 2.6.26
+Contact: "Corentin Chary" <corentincj@iksaif.net>
+Description:
+ Control the camera. 1 means on, 0 means off.
+
+What: /sys/devices/platform/eeepc-laptop/cardr
+Date: May 2008
+KernelVersion: 2.6.26
+Contact: "Corentin Chary" <corentincj@iksaif.net>
+Description:
+ Control the card reader. 1 means on, 0 means off.
+
+What: /sys/devices/platform/eeepc-laptop/cpufv
+Date: Jun 2009
+KernelVersion: 2.6.31
+Contact: "Corentin Chary" <corentincj@iksaif.net>
+Description:
+ Change CPU clock configuration.
+ On the Eee PC 1000H there are three available clock configuration:
+ * 0 -> Super Performance Mode
+ * 1 -> High Performance Mode
+ * 2 -> Power Saving Mode
+ On Eee PC 701 there is only 2 available clock configurations.
+ Available configuration are listed in available_cpufv file.
+ Reading this file will show the raw hexadecimal value which
+ is defined as follow:
+ | 8 bit | 8 bit |
+ | `---- Current mode
+ `------------ Availables modes
+ For example, 0x301 means: mode 1 selected, 3 available modes.
+
+What: /sys/devices/platform/eeepc-laptop/available_cpufv
+Date: Jun 2009
+KernelVersion: 2.6.31
+Contact: "Corentin Chary" <corentincj@iksaif.net>
+Description:
+ List available cpufv modes.
diff --git a/Documentation/hwmon/acpi_power_meter b/Documentation/hwmon/acpi_power_meter
new file mode 100644
index 000000000000..c80399a00c50
--- /dev/null
+++ b/Documentation/hwmon/acpi_power_meter
@@ -0,0 +1,51 @@
+Kernel driver power_meter
+=========================
+
+This driver talks to ACPI 4.0 power meters.
+
+Supported systems:
+ * Any recent system with ACPI 4.0.
+ Prefix: 'power_meter'
+ Datasheet: http://acpi.info/, section 10.4.
+
+Author: Darrick J. Wong
+
+Description
+-----------
+
+This driver implements sensor reading support for the power meters exposed in
+the ACPI 4.0 spec (Chapter 10.4). These devices have a simple set of
+features--a power meter that returns average power use over a configurable
+interval, an optional capping mechanism, and a couple of trip points. The
+sysfs interface conforms with the specification outlined in the "Power" section
+of Documentation/hwmon/sysfs-interface.
+
+Special Features
+----------------
+
+The power[1-*]_is_battery knob indicates if the power supply is a battery.
+Both power[1-*]_average_{min,max} must be set before the trip points will work.
+When both of them are set, an ACPI event will be broadcast on the ACPI netlink
+socket and a poll notification will be sent to the appropriate
+power[1-*]_average sysfs file.
+
+The power[1-*]_{model_number, serial_number, oem_info} fields display arbitrary
+strings that ACPI provides with the meter. The measures/ directory contains
+symlinks to the devices that this meter measures.
+
+Some computers have the ability to enforce a power cap in hardware. If this is
+the case, the power[1-*]_cap and related sysfs files will appear. When the
+average power consumption exceeds the cap, an ACPI event will be broadcast on
+the netlink event socket and a poll notification will be sent to the
+appropriate power[1-*]_alarm file to indicate that capping has begun, and the
+hardware has taken action to reduce power consumption. Most likely this will
+result in reduced performance.
+
+There are a few other ACPI notifications that can be sent by the firmware. In
+all cases the ACPI event will be broadcast on the ACPI netlink event socket as
+well as sent as a poll notification to a sysfs file. The events are as
+follows:
+
+power[1-*]_cap will be notified if the firmware changes the power cap.
+power[1-*]_interval will be notified if the firmware changes the averaging
+interval.
diff --git a/Documentation/laptops/asus-laptop.txt b/Documentation/laptops/asus-laptop.txt
new file mode 100644
index 000000000000..c1c5be84e4b1
--- /dev/null
+++ b/Documentation/laptops/asus-laptop.txt
@@ -0,0 +1,258 @@
+Asus Laptop Extras
+
+Version 0.1
+August 6, 2009
+
+Corentin Chary <corentincj@iksaif.net>
+http://acpi4asus.sf.net/
+
+ This driver provides support for extra features of ACPI-compatible ASUS laptops.
+ It may also support some MEDION, JVC or VICTOR laptops (such as MEDION 9675 or
+ VICTOR XP7210 for example). It makes all the extra buttons generate standard
+ ACPI events that go through /proc/acpi/events and input events (like keyboards).
+ On some models adds support for changing the display brightness and output,
+ switching the LCD backlight on and off, and most importantly, allows you to
+ blink those fancy LEDs intended for reporting mail and wireless status.
+
+This driver supercedes the old asus_acpi driver.
+
+Requirements
+------------
+
+ Kernel 2.6.X sources, configured for your computer, with ACPI support.
+ You also need CONFIG_INPUT and CONFIG_ACPI.
+
+Status
+------
+
+ The features currently supported are the following (see below for
+ detailed description):
+
+ - Fn key combinations
+ - Bluetooth enable and disable
+ - Wlan enable and disable
+ - GPS enable and disable
+ - Video output switching
+ - Ambient Light Sensor on and off
+ - LED control
+ - LED Display control
+ - LCD brightness control
+ - LCD on and off
+
+ A compatibility table by model and feature is maintained on the web
+ site, http://acpi4asus.sf.net/.
+
+Usage
+-----
+
+ Try "modprobe asus_acpi". Check your dmesg (simply type dmesg). You should
+ see some lines like this :
+
+ Asus Laptop Extras version 0.42
+ L2D model detected.
+
+ If it is not the output you have on your laptop, send it (and the laptop's
+ DSDT) to me.
+
+ That's all, now, all the events generated by the hotkeys of your laptop
+ should be reported in your /proc/acpi/event entry. You can check with
+ "acpi_listen".
+
+ Hotkeys are also reported as input keys (like keyboards) you can check
+ which key are supported using "xev" under X11.
+
+ You can get informations on the version of your DSDT table by reading the
+ /sys/devices/platform/asus-laptop/infos entry. If you have a question or a
+ bug report to do, please include the output of this entry.
+
+LEDs
+----
+
+ You can modify LEDs be echoing values to /sys/class/leds/asus::*/brightness :
+ echo 1 > /sys/class/leds/asus::mail/brightness
+ will switch the mail LED on.
+ You can also know if they are on/off by reading their content and use
+ kernel triggers like ide-disk or heartbeat.
+
+Backlight
+---------
+
+ You can control lcd backlight power and brightness with
+ /sys/class/backlight/asus-laptop/. Brightness Values are between 0 and 15.
+
+Wireless devices
+---------------
+
+ You can turn the internal Bluetooth adapter on/off with the bluetooth entry
+ (only on models with Bluetooth). This usually controls the associated LED.
+ Same for Wlan adapter.
+
+Display switching
+-----------------
+
+ Note: the display switching code is currently considered EXPERIMENTAL.
+
+ Switching works for the following models:
+ L3800C
+ A2500H
+ L5800C
+ M5200N
+ W1000N (albeit with some glitches)
+ M6700R
+ A6JC
+ F3J
+
+ Switching doesn't work for the following:
+ M3700N
+ L2X00D (locks the laptop under certain conditions)
+
+ To switch the displays, echo values from 0 to 15 to
+ /sys/devices/platform/asus-laptop/display. The significance of those values
+ is as follows:
+
+ +-------+-----+-----+-----+-----+-----+
+ | Bin | Val | DVI | TV | CRT | LCD |
+ +-------+-----+-----+-----+-----+-----+
+ + 0000 + 0 + + + + +
+ +-------+-----+-----+-----+-----+-----+
+ + 0001 + 1 + + + + X +
+ +-------+-----+-----+-----+-----+-----+
+ + 0010 + 2 + + + X + +
+ +-------+-----+-----+-----+-----+-----+
+ + 0011 + 3 + + + X + X +
+ +-------+-----+-----+-----+-----+-----+
+ + 0100 + 4 + + X + + +
+ +-------+-----+-----+-----+-----+-----+
+ + 0101 + 5 + + X + + X +
+ +-------+-----+-----+-----+-----+-----+
+ + 0110 + 6 + + X + X + +
+ +-------+-----+-----+-----+-----+-----+
+ + 0111 + 7 + + X + X + X +
+ +-------+-----+-----+-----+-----+-----+
+ + 1000 + 8 + X + + + +
+ +-------+-----+-----+-----+-----+-----+
+ + 1001 + 9 + X + + + X +
+ +-------+-----+-----+-----+-----+-----+
+ + 1010 + 10 + X + + X + +
+ +-------+-----+-----+-----+-----+-----+
+ + 1011 + 11 + X + + X + X +
+ +-------+-----+-----+-----+-----+-----+
+ + 1100 + 12 + X + X + + +
+ +-------+-----+-----+-----+-----+-----+
+ + 1101 + 13 + X + X + + X +
+ +-------+-----+-----+-----+-----+-----+
+ + 1110 + 14 + X + X + X + +
+ +-------+-----+-----+-----+-----+-----+
+ + 1111 + 15 + X + X + X + X +
+ +-------+-----+-----+-----+-----+-----+
+
+ In most cases, the appropriate displays must be plugged in for the above
+ combinations to work. TV-Out may need to be initialized at boot time.
+
+ Debugging:
+ 1) Check whether the Fn+F8 key:
+ a) does not lock the laptop (try disabling CONFIG_X86_UP_APIC or boot with
+ noapic / nolapic if it does)
+ b) generates events (0x6n, where n is the value corresponding to the
+ configuration above)
+ c) actually works
+ Record the disp value at every configuration.
+ 2) Echo values from 0 to 15 to /sys/devices/platform/asus-laptop/display.
+ Record its value, note any change. If nothing changes, try a broader range,
+ up to 65535.
+ 3) Send ANY output (both positive and negative reports are needed, unless your
+ machine is already listed above) to the acpi4asus-user mailing list.
+
+ Note: on some machines (e.g. L3C), after the module has been loaded, only 0x6n
+ events are generated and no actual switching occurs. In such a case, a line
+ like:
+
+ echo $((10#$arg-60)) > /sys/devices/platform/asus-laptop/display
+
+ will usually do the trick ($arg is the 0000006n-like event passed to acpid).
+
+ Note: there is currently no reliable way to read display status on xxN
+ (Centrino) models.
+
+LED display
+-----------
+
+ Some models like the W1N have a LED display that can be used to display
+ several informations.
+
+ LED display works for the following models:
+ W1000N
+ W1J
+
+ To control the LED display, use the following :
+
+ echo 0x0T000DDD > /sys/devices/platform/asus-laptop/
+
+ where T control the 3 letters display, and DDD the 3 digits display,
+ according to the tables below.
+
+ DDD (digits)
+ 000 to 999 = display digits
+ AAA = ---
+ BBB to FFF = turn-off
+
+ T (type)
+ 0 = off
+ 1 = dvd
+ 2 = vcd
+ 3 = mp3
+ 4 = cd
+ 5 = tv
+ 6 = cpu
+ 7 = vol
+
+ For example "echo 0x01000001 >/sys/devices/platform/asus-laptop/ledd"
+ would display "DVD001".
+
+Driver options:
+---------------
+
+ Options can be passed to the asus-laptop driver using the standard
+ module argument syntax (<param>=<value> when passing the option to the
+ module or asus-laptop.<param>=<value> on the kernel boot line when
+ asus-laptop is statically linked into the kernel).
+
+ wapf: WAPF defines the behavior of the Fn+Fx wlan key
+ The significance of values is yet to be found, but
+ most of the time:
+ - 0x0 should do nothing
+ - 0x1 should allow to control the device with Fn+Fx key.
+ - 0x4 should send an ACPI event (0x88) while pressing the Fn+Fx key
+ - 0x5 like 0x1 or 0x4
+
+ The default value is 0x1.
+
+Unsupported models
+------------------
+
+ These models will never be supported by this module, as they use a completely
+ different mechanism to handle LEDs and extra stuff (meaning we have no clue
+ how it works):
+
+ - ASUS A1300 (A1B), A1370D
+ - ASUS L7300G
+ - ASUS L8400
+
+Patches, Errors, Questions:
+--------------------------
+
+ I appreciate any success or failure
+ reports, especially if they add to or correct the compatibility table.
+ Please include the following information in your report:
+
+ - Asus model name
+ - a copy of your ACPI tables, using the "acpidump" utility
+ - a copy of /sys/devices/platform/asus-laptop/infos
+ - which driver features work and which don't
+ - the observed behavior of non-working features
+
+ Any other comments or patches are also more than welcome.
+
+ acpi4asus-user@lists.sourceforge.net
+ http://sourceforge.net/projects/acpi4asus
+
diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index e2ddcdeb61b6..6d03487ef1c7 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -219,7 +219,7 @@ The following commands can be written to the /proc/acpi/ibm/hotkey file:
echo 0xffffffff > /proc/acpi/ibm/hotkey -- enable all hot keys
echo 0 > /proc/acpi/ibm/hotkey -- disable all possible hot keys
... any other 8-hex-digit mask ...
- echo reset > /proc/acpi/ibm/hotkey -- restore the original mask
+ echo reset > /proc/acpi/ibm/hotkey -- restore the recommended mask
The following commands have been deprecated and will cause the kernel
to log a warning:
@@ -240,9 +240,13 @@ sysfs notes:
Returns 0.
hotkey_bios_mask:
+ DEPRECATED, DON'T USE, WILL BE REMOVED IN THE FUTURE.
+
Returns the hot keys mask when thinkpad-acpi was loaded.
Upon module unload, the hot keys mask will be restored
- to this value.
+ to this value. This is always 0x80c, because those are
+ the hotkeys that were supported by ancient firmware
+ without mask support.
hotkey_enable:
DEPRECATED, WILL BE REMOVED SOON.
diff --git a/Documentation/leds-class.txt b/Documentation/leds-class.txt
index 6399557cdab3..8fd5ca2ae32d 100644
--- 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