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Commit 7d5a015e authored by Henrique de Moraes Holschuh's avatar Henrique de Moraes Holschuh Committed by Len Brown
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ACPI: thinkpad-acpi: update brightness sysfs interface support 



Update the brightness sysfs interface (done through the backlight class) to
be in line with the rest of the thinkpad-acpi driver.

This renames the incorrect, un-obvious, and clash-prone name of "ibm" for
the backlight device to a much more fitting and descriptive
"thinkpad_screen".  This is something I wanted to do for quite a while...

Signed-off-by: default avatarHenrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent b616004c

Documentation/thinkpad-acpi.txt

+46 −6
Original line number Diff line number Diff line
@@ -611,19 +611,59 @@ registers contain the current battery capacity, etc. If you experiment 
with this, do send me your results (including some complete dumps with

a description of the conditions when they were taken.)



LCD brightness control -- /proc/acpi/ibm/brightness

---------------------------------------------------

LCD brightness control

----------------------



procfs: /proc/acpi/ibm/brightness

sysfs backlight device "thinkpad_screen"



This feature allows software control of the LCD brightness on ThinkPad

models which don't have a hardware brightness slider. The available

commands are:

models which don't have a hardware brightness slider.



It has some limitations: the LCD backlight cannot be actually turned on or off

by this interface, and in many ThinkPad models, the "dim while on battery"

functionality will be enabled by the BIOS when this interface is used, and

cannot be controlled.



The backlight control has eight levels, ranging from 0 to 7.  Some of the

levels may not be distinct.



Procfs notes:



	The available commands are:



	echo up   >/proc/acpi/ibm/brightness

	echo down >/proc/acpi/ibm/brightness

	echo 'level <level>' >/proc/acpi/ibm/brightness



The <level> number range is 0 to 7, although not all of them may be

distinct. The current brightness level is shown in the file.

Sysfs notes:



The interface is implemented through the backlight sysfs class, which is poorly

documented at this time.



Locate the thinkpad_screen device under /sys/class/backlight, and inside it

there will be the following attributes:



	max_brightness:

		Reads the maximum brightness the hardware can be set to.

		The minimum is always zero.



	actual_brightness:

		Reads what brightness the screen is set to at this instant.



	brightness:

		Writes request the driver to change brightness to the given

		value.  Reads will tell you what brightness the driver is trying

		to set the display to when "power" is set to zero and the display

		has not been dimmed by a kernel power management event.



	power:

		power management mode, where 0 is "display on", and 1 to 3 will

		dim the display backlight to brightness level 0 because

		thinkpad-acpi cannot really turn the backlight off.  Kernel

		power management events can temporarily increase the current

		power management level, i.e. they can dim the display.





Volume control -- /proc/acpi/ibm/volume

---------------------------------------

drivers/misc/thinkpad_acpi.c

+3 −2
Original line number Diff line number Diff line
@@ -2414,7 +2414,8 @@ static int __init brightness_init(struct ibm_init_struct *iibm) 
	if (b < 0)

		return b;



	ibm_backlight_device = backlight_device_register("ibm", NULL, NULL,

	ibm_backlight_device = backlight_device_register(

					TPACPI_BACKLIGHT_DEV_NAME, NULL, NULL,

					&ibm_backlight_data);

	if (IS_ERR(ibm_backlight_device)) {

		printk(IBM_ERR "Could not register backlight device\n");

drivers/misc/thinkpad_acpi.h

+2 −0
Original line number Diff line number Diff line
@@ -296,6 +296,8 @@ static int bluetooth_write(char *buf); 
 * Brightness (backlight) subdriver

 */



#define TPACPI_BACKLIGHT_DEV_NAME "thinkpad_screen"



static struct backlight_device *ibm_backlight_device;

static int brightness_offset = 0x31;