Input: wacom - add Intuos4 LED and OLED control

This commit enables control of the LEDs and OLED displays found on the
Wacom Intuos4 M, L, and XL. For this purpose, a new "wacom_led" attribute
group is added to the sysfs entry of the USB device.

This "wacom_led" group only shows up when the correct device (M, L, or XL)
is detected. The attributes are described in
 Documentation/ABI/testing/sysfs-wacom

Signed-off-by: Eduard Hasenleithner <eduard@hasenleithner.at>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

Documentation/ABI/testing/sysfs-driver-wacom

@@ -0,0 +1,64 @@
+What:		/sys/class/hidraw/hidraw*/device/speed
+Date:		April 2010
+Kernel Version:	2.6.35
+Contact:	linux-bluetooth@vger.kernel.org
+Description:
+		The /sys/class/hidraw/hidraw*/device/speed file controls
+		reporting speed of Wacom bluetooth tablet. Reading from
+		this file returns 1 if tablet reports in high speed mode
+		or 0 otherwise. Writing to this file one of these values
+		switches reporting speed.
+
+What:		/sys/bus/usb/devices/<busnum>-<devnum>:<cfg>.<intf>/wacom_led/led
+Date:		August 2011
+Contact:	linux-input@vger.kernel.org
+Description:
+		Attribute group for control of the status LEDs and the OLED
+		displays found on the Wacom Intuos 4 M, L, and XL tablets. This
+		attribute group is not available for other Wacom tablets.
+		Therefore its presence implicitly signifies the presence of
+		said LEDs and OLED displays on the tablet device.
+
+What:		/sys/bus/usb/devices/<busnum>-<devnum>:<cfg>.<intf>/wacom_led/status0_luminance
+Date:		August 2011
+Contact:	linux-input@vger.kernel.org
+Description:
+		Writing to this file sets the status LED luminance (0..127)
+		when the stylus does not touch the tablet surface, and no
+		button is pressed on the stylus.
+
+What:		/sys/bus/usb/devices/<busnum>-<devnum>:<cfg>.<intf>/wacom_led/status1_luminance
+Date:		August 2011
+Contact:	linux-input@vger.kernel.org
+Description:
+		Writing to this file sets the status LED luminance (0..127)
+		when the stylus touches the tablet surface, or any button is
+		pressed on the stylus.
+
+What:		/sys/bus/usb/devices/<busnum>-<devnum>:<cfg>.<intf>/wacom_led/status_led_select
+Date:		August 2011
+Contact:	linux-input@vger.kernel.org
+Description:
+		Writing to this file sets which one of the four status LEDs is
+		active (0..3). The other three LEDs are always inactive.  By
+		means of specifying "-1" it is possible to set all status LEDs
+		to inactive.
+
+What:		/sys/bus/usb/devices/<busnum>-<devnum>:<cfg>.<intf>/wacom_led/buttons_luminance
+Date:		August 2011
+Contact:	linux-input@vger.kernel.org
+Description:
+		Writing to this file sets the overall luminance level (0..15)
+		of all eight button OLED displays.
+
+What:		/sys/bus/usb/devices/<busnum>-<devnum>:<cfg>.<intf>/wacom_led/button<n>_rawimg
+Date:		August 2011
+Contact:	linux-input@vger.kernel.org
+Description:
+		When writing a 1024 byte raw image in Wacom Intuos 4
+		interleaving format to the file, the image shows up on Button N
+		of the device. The image is a 64x32 pixel 4-bit gray image. The
+		1024 byte binary is split up into 16x 64 byte chunks. Each 64
+		byte chunk encodes the image data for two consecutive lines on
+		the display. The low nibble of each byte contains the first
+		line, and the high nibble contains the second line.

drivers/input/tablet/wacom.h

@@ -114,6 +114,12 @@ struct wacom {
 	struct mutex lock;
 	bool open;
 	char phys[32];
+	struct wacom_led {
+		u8 select; /* status led selector (0..3, -1=none) */
+		u8 llv;    /* status led brightness no button */
+		u8 hlv;    /* status led brightness button pressed */
+		u8 img_lum;   /* OLED matrix display brightness */
+	} led;
 };
 
 extern const struct usb_device_id wacom_ids[];