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authorLinus Torvalds <torvalds@linux-foundation.org>2009-09-23 12:32:11 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-23 12:32:11 -0400
commitc11f6c82581e8be4e1829c677db54e7f55cebece (patch)
tree1a116241b0831ded998aabe800bdc24104cbd826 /Documentation
parent40aba218969914d1b225e742617adb921cf94eae (diff)
parent193a6dec1c0246a80b6d0101e4f351ccf877bcac (diff)
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 @@
1What: /sys/class/backlight/<backlight>/bl_power
2Date: April 2005
3KernelVersion: 2.6.12
4Contact: Richard Purdie <rpurdie@rpsys.net>
5Description:
6 Control BACKLIGHT power, values are FB_BLANK_* from fb.h
7 - FB_BLANK_UNBLANK (0) : power on.
8 - FB_BLANK_POWERDOWN (4) : power off
9Users: HAL
10
11What: /sys/class/backlight/<backlight>/brightness
12Date: April 2005
13KernelVersion: 2.6.12
14Contact: Richard Purdie <rpurdie@rpsys.net>
15Description:
16 Control the brightness for this <backlight>. Values
17 are between 0 and max_brightness. This file will also
18 show the brightness level stored in the driver, which
19 may not be the actual brightness (see actual_brightness).
20Users: HAL
21
22What: /sys/class/backlight/<backlight>/actual_brightness
23Date: March 2006
24KernelVersion: 2.6.17
25Contact: Richard Purdie <rpurdie@rpsys.net>
26Description:
27 Show the actual brightness by querying the hardware.
28Users: HAL
29
30What: /sys/class/backlight/<backlight>/max_brightness
31Date: April 2005
32KernelVersion: 2.6.12
33Contact: Richard Purdie <rpurdie@rpsys.net>
34Description:
35 Maximum brightness for <backlight>.
36Users: 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 @@
1What: /sys/class/lcd/<lcd>/lcd_power
2Date: April 2005
3KernelVersion: 2.6.12
4Contact: Richard Purdie <rpurdie@rpsys.net>
5Description:
6 Control LCD power, values are FB_BLANK_* from fb.h
7 - FB_BLANK_UNBLANK (0) : power on.
8 - FB_BLANK_POWERDOWN (4) : power off
9
10What: /sys/class/lcd/<lcd>/contrast
11Date: April 2005
12KernelVersion: 2.6.12
13Contact: Richard Purdie <rpurdie@rpsys.net>
14Description:
15 Current contrast of this LCD device. Value is between 0 and
16 /sys/class/lcd/<lcd>/max_contrast.
17
18What: /sys/class/lcd/<lcd>/max_contrast
19Date: April 2005
20KernelVersion: 2.6.12
21Contact: Richard Purdie <rpurdie@rpsys.net>
22Description:
23 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 @@
1What: /sys/class/leds/<led>/brightness
2Date: March 2006
3KernelVersion: 2.6.17
4Contact: Richard Purdie <rpurdie@rpsys.net>
5Description:
6 Set the brightness of the LED. Most LEDs don't
7 have hardware brightness support so will just be turned on for
8 non-zero brightness settings. The value is between 0 and
9 /sys/class/leds/<led>/max_brightness.
10
11What: /sys/class/leds/<led>/max_brightness
12Date: March 2006
13KernelVersion: 2.6.17
14Contact: Richard Purdie <rpurdie@rpsys.net>
15Description:
16 Maximum brightness level for this led, default is 255 (LED_FULL).
17
18What: /sys/class/leds/<led>/trigger
19Date: March 2006
20KernelVersion: 2.6.17
21Contact: Richard Purdie <rpurdie@rpsys.net>
22Description:
23 Set the trigger for this LED. A trigger is a kernel based source
24 of led events.
25 You can change triggers in a similar manner to the way an IO
26 scheduler is chosen. Trigger specific parameters can appear in
27 /sys/class/leds/<led> once a given trigger is selected.
28
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 @@
1What: /sys/devices/platform/asus-laptop/display
2Date: January 2007
3KernelVersion: 2.6.20
4Contact: "Corentin Chary" <corentincj@iksaif.net>
5Description:
6 This file allows display switching. The value
7 is composed by 4 bits and defined as follow:
8 4321
9 |||`- LCD
10 ||`-- CRT
11 |`--- TV
12 `---- DVI
13 Ex: - 0 (0000b) means no display
14 - 3 (0011b) CRT+LCD.
15
16What: /sys/devices/platform/asus-laptop/gps
17Date: January 2007
18KernelVersion: 2.6.20
19Contact: "Corentin Chary" <corentincj@iksaif.net>
20Description:
21 Control the gps device. 1 means on, 0 means off.
22Users: Lapsus
23
24What: /sys/devices/platform/asus-laptop/ledd
25Date: January 2007
26KernelVersion: 2.6.20
27Contact: "Corentin Chary" <corentincj@iksaif.net>
28Description:
29 Some models like the W1N have a LED display that can be
30 used to display several informations.
31 To control the LED display, use the following :
32 echo 0x0T000DDD > /sys/devices/platform/asus-laptop/
33 where T control the 3 letters display, and DDD the 3 digits display.
34 The DDD table can be found in Documentation/laptops/asus-laptop.txt
35
36What: /sys/devices/platform/asus-laptop/bluetooth
37Date: January 2007
38KernelVersion: 2.6.20
39Contact: "Corentin Chary" <corentincj@iksaif.net>
40Description:
41 Control the bluetooth device. 1 means on, 0 means off.
42 This may control the led, the device or both.
43Users: Lapsus
44
45What: /sys/devices/platform/asus-laptop/wlan
46Date: January 2007
47KernelVersion: 2.6.20
48Contact: "Corentin Chary" <corentincj@iksaif.net>
49Description:
50 Control the bluetooth device. 1 means on, 0 means off.
51 This may control the led, the device or both.
52Users: 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 @@
1What: /sys/devices/platform/eeepc-laptop/disp
2Date: May 2008
3KernelVersion: 2.6.26
4Contact: "Corentin Chary" <corentincj@iksaif.net>
5Description:
6 This file allows display switching.
7 - 1 = LCD
8 - 2 = CRT
9 - 3 = LCD+CRT
10 If you run X11, you should use xrandr instead.
11
12What: /sys/devices/platform/eeepc-laptop/camera
13Date: May 2008
14KernelVersion: 2.6.26
15Contact: "Corentin Chary" <corentincj@iksaif.net>
16Description:
17 Control the camera. 1 means on, 0 means off.
18
19What: /sys/devices/platform/eeepc-laptop/cardr
20Date: May 2008
21KernelVersion: 2.6.26
22Contact: "Corentin Chary" <corentincj@iksaif.net>
23Description:
24 Control the card reader. 1 means on, 0 means off.
25
26What: /sys/devices/platform/eeepc-laptop/cpufv
27Date: Jun 2009
28KernelVersion: 2.6.31
29Contact: "Corentin Chary" <corentincj@iksaif.net>
30Description:
31 Change CPU clock configuration.
32 On the Eee PC 1000H there are three available clock configuration:
33 * 0 -> Super Performance Mode
34 * 1 -> High Performance Mode
35 * 2 -> Power Saving Mode
36 On Eee PC 701 there is only 2 available clock configurations.
37 Available configuration are listed in available_cpufv file.
38 Reading this file will show the raw hexadecimal value which
39 is defined as follow:
40 | 8 bit | 8 bit |
41 | `---- Current mode
42 `------------ Availables modes
43 For example, 0x301 means: mode 1 selected, 3 available modes.
44
45What: /sys/devices/platform/eeepc-laptop/available_cpufv
46Date: Jun 2009
47KernelVersion: 2.6.31
48Contact: "Corentin Chary" <corentincj@iksaif.net>
49Description:
50 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 @@
1Kernel driver power_meter
2=========================
3
4This driver talks to ACPI 4.0 power meters.
5
6Supported systems:
7 * Any recent system with ACPI 4.0.
8 Prefix: 'power_meter'
9 Datasheet: http://acpi.info/, section 10.4.
10
11Author: Darrick J. Wong
12
13Description
14-----------
15
16This driver implements sensor reading support for the power meters exposed in
17the ACPI 4.0 spec (Chapter 10.4). These devices have a simple set of
18features--a power meter that returns average power use over a configurable
19interval, an optional capping mechanism, and a couple of trip points. The
20sysfs interface conforms with the specification outlined in the "Power" section
21of Documentation/hwmon/sysfs-interface.
22
23Special Features
24----------------
25
26The power[1-*]_is_battery knob indicates if the power supply is a battery.
27Both power[1-*]_average_{min,max} must be set before the trip points will work.
28When both of them are set, an ACPI event will be broadcast on the ACPI netlink
29socket and a poll notification will be sent to the appropriate
30power[1-*]_average sysfs file.
31
32The power[1-*]_{model_number, serial_number, oem_info} fields display arbitrary
33strings that ACPI provides with the meter. The measures/ directory contains
34symlinks to the devices that this meter measures.
35
36Some computers have the ability to enforce a power cap in hardware. If this is
37the case, the power[1-*]_cap and related sysfs files will appear. When the
38average power consumption exceeds the cap, an ACPI event will be broadcast on
39the netlink event socket and a poll notification will be sent to the
40appropriate power[1-*]_alarm file to indicate that capping has begun, and the
41hardware has taken action to reduce power consumption. Most likely this will
42result in reduced performance.
43
44There are a few other ACPI notifications that can be sent by the firmware. In
45all cases the ACPI event will be broadcast on the ACPI netlink event socket as
46well as sent as a poll notification to a sysfs file. The events are as
47follows:
48
49power[1-*]_cap will be notified if the firmware changes the power cap.
50power[1-*]_interval will be notified if the firmware changes the averaging
51interval.
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 @@
1Asus Laptop Extras
2
3Version 0.1
4August 6, 2009
5
6Corentin Chary <corentincj@iksaif.net>
7http://acpi4asus.sf.net/
8
9 This driver provides support for extra features of ACPI-compatible ASUS laptops.
10 It may also support some MEDION, JVC or VICTOR laptops (such as MEDION 9675 or
11 VICTOR XP7210 for example). It makes all the extra buttons generate standard
12 ACPI events that go through /proc/acpi/events and input events (like keyboards).
13 On some models adds support for changing the display brightness and output,
14 switching the LCD backlight on and off, and most importantly, allows you to
15 blink those fancy LEDs intended for reporting mail and wireless status.
16
17This driver supercedes the old asus_acpi driver.
18
19Requirements
20------------
21
22 Kernel 2.6.X sources, configured for your computer, with ACPI support.
23 You also need CONFIG_INPUT and CONFIG_ACPI.
24
25Status
26------
27
28 The features currently supported are the following (see below for
29 detailed description):
30
31 - Fn key combinations
32 - Bluetooth enable and disable
33 - Wlan enable and disable
34 - GPS enable and disable
35 - Video output switching
36 - Ambient Light Sensor on and off
37 - LED control
38 - LED Display control
39 - LCD brightness control
40 - LCD on and off
41
42 A compatibility table by model and feature is maintained on the web
43 site, http://acpi4asus.sf.net/.
44
45Usage
46-----
47
48 Try "modprobe asus_acpi". Check your dmesg (simply type dmesg). You should
49 see some lines like this :
50
51 Asus Laptop Extras version 0.42
52 L2D model detected.
53
54 If it is not the output you have on your laptop, send it (and the laptop's
55 DSDT) to me.
56
57 That's all, now, all the events generated by the hotkeys of your laptop
58 should be reported in your /proc/acpi/event entry. You can check with
59 "acpi_listen".
60
61 Hotkeys are also reported as input keys (like keyboards) you can check
62 which key are supported using "xev" under X11.
63
64 You can get informations on the version of your DSDT table by reading the
65 /sys/devices/platform/asus-laptop/infos entry. If you have a question or a
66 bug report to do, please include the output of this entry.
67
68LEDs
69----
70
71 You can modify LEDs be echoing values to /sys/class/leds/asus::*/brightness :
72 echo 1 > /sys/class/leds/asus::mail/brightness
73 will switch the mail LED on.
74 You can also know if they are on/off by reading their content and use
75 kernel triggers like ide-disk or heartbeat.
76
77Backlight
78---------
79
80 You can control lcd backlight power and brightness with
81 /sys/class/backlight/asus-laptop/. Brightness Values are between 0 and 15.
82
83Wireless devices
84---------------
85
86 You can turn the internal Bluetooth adapter on/off with the bluetooth entry
87 (only on models with Bluetooth). This usually controls the associated LED.
88 Same for Wlan adapter.
89
90Display switching
91-----------------
92
93 Note: the display switching code is currently considered EXPERIMENTAL.
94
95 Switching works for the following models:
96 L3800C
97 A2500H
98 L5800C
99 M5200N
100 W1000N (albeit with some glitches)
101 M6700R
102 A6JC
103 F3J
104
105 Switching doesn't work for the following:
106 M3700N
107 L2X00D (locks the laptop under certain conditions)
108
109 To switch the displays, echo values from 0 to 15 to
110 /sys/devices/platform/asus-laptop/display. The significance of those values
111 is as follows:
112
113 +-------+-----+-----+-----+-----+-----+
114 | Bin | Val | DVI | TV | CRT | LCD |
115 +-------+-----+-----+-----+-----+-----+
116 + 0000 + 0 + + + + +
117 +-------+-----+-----+-----+-----+-----+
118 + 0001 + 1 + + + + X +
119 +-------+-----+-----+-----+-----+-----+
120 + 0010 + 2 + + + X + +
121 +-------+-----+-----+-----+-----+-----+
122 + 0011 + 3 + + + X + X +
123 +-------+-----+-----+-----+-----+-----+
124 + 0100 + 4 + + X + + +
125 +-------+-----+-----+-----+-----+-----+
126 + 0101 + 5 + + X + + X +
127 +-------+-----+-----+-----+-----+-----+
128 + 0110 + 6 + + X + X + +
129 +-------+-----+-----+-----+-----+-----+
130 + 0111 + 7 + + X + X + X +
131 +-------+-----+-----+-----+-----+-----+
132 + 1000 + 8 + X + + + +
133 +-------+-----+-----+-----+-----+-----+
134 + 1001 + 9 + X + + + X +
135 +-------+-----+-----+-----+-----+-----+
136 + 1010 + 10 + X + + X + +
137 +-------+-----+-----+-----+-----+-----+
138 + 1011 + 11 + X + + X + X +
139 +-------+-----+-----+-----+-----+-----+
140 + 1100 + 12 + X + X + + +
141 +-------+-----+-----+-----+-----+-----+
142 + 1101 + 13 + X + X + + X +
143 +-------+-----+-----+-----+-----+-----+
144 + 1110 + 14 + X + X + X + +
145 +-------+-----+-----+-----+-----+-----+
146 + 1111 + 15 + X + X + X + X +
147 +-------+-----+-----+-----+-----+-----+
148
149 In most cases, the appropriate displays must be plugged in for the above
150 combinations to work. TV-Out may need to be initialized at boot time.
151
152 Debugging:
153 1) Check whether the Fn+F8 key:
154 a) does not lock the laptop (try disabling CONFIG_X86_UP_APIC or boot with
155 noapic / nolapic if it does)
156 b) generates events (0x6n, where n is the value corresponding to the
157 configuration above)
158 c) actually works
159 Record the disp value at every configuration.
160 2) Echo values from 0 to 15 to /sys/devices/platform/asus-laptop/display.
161 Record its value, note any change. If nothing changes, try a broader range,
162 up to 65535.
163 3) Send ANY output (both positive and negative reports are needed, unless your
164 machine is already listed above) to the acpi4asus-user mailing list.
165
166 Note: on some machines (e.g. L3C), after the module has been loaded, only 0x6n
167 events are generated and no actual switching occurs. In such a case, a line
168 like:
169
170 echo $((10#$arg-60)) > /sys/devices/platform/asus-laptop/display
171
172 will usually do the trick ($arg is the 0000006n-like event passed to acpid).
173
174 Note: there is currently no reliable way to read display status on xxN
175 (Centrino) models.
176
177LED display
178-----------
179
180 Some models like the W1N have a LED display that can be used to display
181 several informations.
182
183 LED display works for the following models:
184 W1000N
185 W1J
186
187 To control the LED display, use the following :
188
189 echo 0x0T000DDD > /sys/devices/platform/asus-laptop/
190
191 where T control the 3 letters display, and DDD the 3 digits display,
192 according to the tables below.
193
194 DDD (digits)
195 000 to 999 = display digits
196 AAA = ---
197 BBB to FFF = turn-off
198
199 T (type)
200 0 = off
201 1 = dvd
202 2 = vcd
203 3 = mp3
204 4 = cd
205 5 = tv
206 6 = cpu
207 7 = vol
208
209 For example "echo 0x01000001 >/sys/devices/platform/asus-laptop/ledd"
210 would display "DVD001".
211
212Driver options:
213---------------
214
215 Options can be passed to the asus-laptop driver using the standard
216 module argument syntax (<param>=<value> when passing the option to the
217 module or asus-laptop.<param>=<value> on the kernel boot line when
218 asus-laptop is statically linked into the kernel).
219
220 wapf: WAPF defines the behavior of the Fn+Fx wlan key
221 The significance of values is yet to be found, but
222 most of the time:
223 - 0x0 should do nothing
224 - 0x1 should allow to control the device with Fn+Fx key.
225 - 0x4 should send an ACPI event (0x88) while pressing the Fn+Fx key
226 - 0x5 like 0x1 or 0x4
227
228 The default value is 0x1.
229
230Unsupported models
231------------------
232
233 These models will never be supported by this module, as they use a completely
234 different mechanism to handle LEDs and extra stuff (meaning we have no clue
235 how it works):
236
237 - ASUS A1300 (A1B), A1370D
238 - ASUS L7300G
239 - ASUS L8400
240
241Patches, Errors, Questions:
242--------------------------
243
244 I appreciate any success or failure
245 reports, especially if they add to or correct the compatibility table.
246 Please include the following information in your report:
247
248 - Asus model name
249 - a copy of your ACPI tables, using the "acpidump" utility
250 - a copy of /sys/devices/platform/asus-laptop/infos
251 - which driver features work and which don't
252 - the observed behavior of non-working features
253
254 Any other comments or patches are also more than welcome.
255
256 acpi4asus-user@lists.sourceforge.net
257 http://sourceforge.net/projects/acpi4asus
258
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:
219 echo 0xffffffff > /proc/acpi/ibm/hotkey -- enable all hot keys 219 echo 0xffffffff > /proc/acpi/ibm/hotkey -- enable all hot keys
220 echo 0 > /proc/acpi/ibm/hotkey -- disable all possible hot keys 220 echo 0 > /proc/acpi/ibm/hotkey -- disable all possible hot keys
221 ... any other 8-hex-digit mask ... 221 ... any other 8-hex-digit mask ...
222 echo reset > /proc/acpi/ibm/hotkey -- restore the original mask 222 echo reset > /proc/acpi/ibm/hotkey -- restore the recommended mask
223 223
224The following commands have been deprecated and will cause the kernel 224The following commands have been deprecated and will cause the kernel
225to log a warning: 225to log a warning:
@@ -240,9 +240,13 @@ sysfs notes:
240 Returns 0. 240 Returns 0.
241 241
242 hotkey_bios_mask: 242 hotkey_bios_mask:
243 DEPRECATED, DON'T USE, WILL BE REMOVED IN THE FUTURE.
244
243 Returns the hot keys mask when thinkpad-acpi was loaded. 245 Returns the hot keys mask when thinkpad-acpi was loaded.
244 Upon module unload, the hot keys mask will be restored 246 Upon module unload, the hot keys mask will be restored
245 to this value. 247 to this value. This is always 0x80c, because those are
248 the hotkeys that were supported by ancient firmware
249 without mask support.
246 250
247 hotkey_enable: 251 hotkey_enable:
248 DEPRECATED, WILL BE REMOVED SOON. 252 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 @@
1
1LED handling under Linux 2LED handling under Linux
2======================== 3========================
3 4
@@ -5,10 +6,10 @@ If you're reading this and thinking about keyboard leds, these are
5handled by the input subsystem and the led class is *not* needed. 6handled by the input subsystem and the led class is *not* needed.
6 7
7In its simplest form, the LED class just allows control of LEDs from 8In its simplest form, the LED class just allows control of LEDs from
8userspace. LEDs appear in /sys/class/leds/. The brightness file will 9userspace. LEDs appear in /sys/class/leds/. The maximum brightness of the
9set the brightness of the LED (taking a value 0-255). Most LEDs don't 10LED is defined in max_brightness file. The brightness file will set the brightness
10have hardware brightness support so will just be turned on for non-zero 11of the LED (taking a value 0-max_brightness). Most LEDs don't have hardware
11brightness settings. 12brightness support so will just be turned on for non-zero brightness settings.
12 13
13The class also introduces the optional concept of an LED trigger. A trigger 14The class also introduces the optional concept of an LED trigger. A trigger
14is a kernel based source of led events. Triggers can either be simple or 15is a kernel based source of led events. Triggers can either be simple or