sony-laptop: Update docs

Update documentation to be consistent with current implementation
(backlight subsys and platform_device).

Signed-off-by: Mattia Dongili <malattia@linux.it>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 106 insertions, 0 deletions

diff --git a/Documentation/sony-laptop.txt b/Documentation/sony-laptop.txt
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+Sony Notebook Control Driver (SNC) Readme
+-----------------------------------------
+	Copyright (C) 2004- 2005 Stelian Pop <stelian@popies.net>
+	Copyright (C) 2007 Mattia Dongili <malattia@linux.it>
+
+This mini-driver drives the SNC device present in the ACPI BIOS of
+the Sony Vaio laptops.
+
+It gives access to some extra laptop functionalities. In its current
+form, this driver let the user set or query the screen brightness
+through the backlight subsystem and remove/apply power to some devices.
+
+Backlight control:
+------------------
+If your laptop model supports it, you will find sysfs files in the
+/sys/class/backlight/sony/
+directory. You will be able to query and set the current screen
+brightness:
+	brightness		get/set screen brightness (an iteger
+				between 0 and 7)
+	actual_brightness	reading from this file will query the HW
+				to get real brightness value
+	max_brightness		the maximum brightness value
+
+
+Platform specific:
+------------------
+Loading the sony-laptop module will create a
+/sys/devices/platform/sony-laptop/
+directory populated with some files.
+
+You then read/write integer values from/to those files by using
+standard UNIX tools.
+
+The files are:
+	brightness_default	screen brightness which will be set
+				when the laptop will be rebooted
+	cdpower			power on/off the internal CD drive
+	audiopower		power on/off the internal sound card
+	lanpower		power on/off the internal ethernet card
+				(only in debug mode)
+
+Note that some files may be missing if they are not supported
+by your particular laptop model.
+
+Example usage:
+	# echo "1" > /sys/devices/platform/sony-laptop/brightness_default
+sets the lowest screen brightness for the next and later reboots,
+	# echo "8" > /sys/devices/platform/sony-laptop/brightness_default
+sets the highest screen brightness for the next and later reboots,
+	# cat /sys/devices/platform/sony-laptop/brightness_default
+retrieves the value.
+
+	# echo "0" > /sys/devices/platform/sony-laptop/audiopower
+powers off the sound card,
+	# echo "1" > /sys/devices/platform/sony-laptop/audiopower
+powers on the sound card.
+
+Development:
+------------
+
+If you want to help with the development of this driver (and
+you are not afraid of any side effects doing strange things with
+your ACPI BIOS could have on your laptop), load the driver and
+pass the option 'debug=1'.
+
+REPEAT: DON'T DO THIS IF YOU DON'T LIKE RISKY BUSINESS.
+
+In your kernel logs you will find the list of all ACPI methods
+the SNC device has on your laptop. You can see the GCDP/GCDP methods
+used to pwer on/off the CD drive, but there are others.
+
+I HAVE NO IDEA WHAT THOSE METHODS DO.
+
+The sony-laptop driver creates, for some of those methods (the most
+current ones found on several Vaio models), an entry under
+/sys/devices/platform/sony-laptop, just like the 'cdpower' one.
+You can create other entries corresponding to your own laptop methods by
+further editing the source (see the 'sony_acpi_values' table, and add a new
+entry to this table with your get/set method names using the
+HANDLE_NAMES macro).
+
+Your mission, should you accept it, is to try finding out what
+those entries are for, by reading/writing random values from/to those
+files and find out what is the impact on your laptop.
+
+Should you find anything interesting, please report it back to me,
+I will not disavow all knowledge of your actions :)
+
+Bugs/Limitations:
+-----------------
+
+* This driver is not based on official documentation from Sony
+  (because there is none), so there is no guarantee this driver
+  will work at all, or do the right thing. Although this hasn't
+  happened to me, this driver could do very bad things to your
+  laptop, including permanent damage.
+
+* The sony-laptop and sonypi drivers do not interact at all. In the
+  future, sonypi could use sony-laptop to do (part of) its business.
+
+* spicctrl, which is the userspace tool used to communicate with the
+  sonypi driver (through /dev/sonypi) does not try to use the
+  sony-laptop driver. In the future, spicctrl could try sonypi first,
+  and if it isn't present, try sony-laptop instead.
+