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Commit 24d3b774 authored by Henrique de Moraes Holschuh's avatar Henrique de Moraes Holschuh Committed by Len Brown
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ACPI: thinkpad-acpi: allow use of CMOS NVRAM for brightness control 



It appears that Lenovo decided to break the EC brightness control interface
in a weird way in their latest BIOSes.  Fortunately, the old CMOS NVRAM
interface works just fine in such BIOSes.

Add a module parameter that allows the user to select which strategy to use
for brightness control: EC, NVRAM, or both.  By default, do both (which is
the way thinkpad-acpi used to work until now) on IBM ThinkPads, and use
NVRAM only on Lenovo ThinkPads.

Signed-off-by: default avatarHenrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent d5a2f2f1

Documentation/thinkpad-acpi.txt

+6 −0
Original line number Diff line number Diff line
@@ -860,6 +860,12 @@ cannot be controlled. 
The backlight control has eight levels, ranging from 0 to 7.  Some of the

levels may not be distinct.



There are two interfaces to the firmware for brightness control, EC and CMOS.

To select which one should be used, use the brightness_mode module parameter:

brightness_mode=1 selects EC mode, brightness_mode=2 selects CMOS mode,

brightness_mode=3 selects both EC and CMOS.  The driver tries to autodetect

which interface to use.



Procfs notes:



	The available commands are:

drivers/misc/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -150,6 +150,7 @@ config THINKPAD_ACPI 
	depends on X86 && ACPI

	select BACKLIGHT_CLASS_DEVICE

	select HWMON

	select NVRAM

	---help---

	  This is a driver for the IBM and Lenovo ThinkPad laptops. It adds

	  support for Fn-Fx key combinations, Bluetooth control, video

drivers/misc/thinkpad_acpi.c

+53 −9
Original line number Diff line number Diff line
@@ -2953,9 +2953,22 @@ static int __init brightness_init(struct ibm_init_struct *iibm) 


	vdbg_printk(TPACPI_DBG_INIT, "initializing brightness subdriver\n");



	if (!brightness_mode) {

		if (thinkpad_id.vendor == PCI_VENDOR_ID_LENOVO)

			brightness_mode = 2;

		else

			brightness_mode = 3;



		dbg_printk(TPACPI_DBG_INIT, "selected brightness_mode=%d\n",

			brightness_mode);

	}



	if (brightness_mode > 3)

		return -EINVAL;



	b = brightness_get(NULL);

	if (b < 0)

		return b;

		return 1;



	ibm_backlight_device = backlight_device_register(

					TPACPI_BACKLIGHT_DEV_NAME, NULL, NULL,
@@ -2991,13 +3004,35 @@ static int brightness_update_status(struct backlight_device *bd) 
				bd->props.brightness : 0);

}



/*

 * ThinkPads can read brightness from two places: EC 0x31, or

 * CMOS NVRAM byte 0x5E, bits 0-3.

 */

static int brightness_get(struct backlight_device *bd)

{

	u8 level;

	if (!acpi_ec_read(brightness_offset, &level))

	u8 lec = 0, lcmos = 0, level = 0;



	if (brightness_mode & 1) {

		if (!acpi_ec_read(brightness_offset, &lec))

			return -EIO;

		lec &= 7;

		level = lec;

	};

	if (brightness_mode & 2) {

		lcmos = (nvram_read_byte(TP_NVRAM_ADDR_BRIGHTNESS)

			 & TP_NVRAM_MASK_LEVEL_BRIGHTNESS)

			>> TP_NVRAM_POS_LEVEL_BRIGHTNESS;

		level = lcmos;

	}



	level &= 0x7;

	if (brightness_mode == 3 && lec != lcmos) {

		printk(IBM_ERR

			"CMOS NVRAM (%u) and EC (%u) do not agree "

			"on display brightness level\n",

			(unsigned int) lcmos,

			(unsigned int) lec);

		return -EIO;

	}



	return level;

}
@@ -3007,14 +3042,20 @@ static int brightness_set(int value) 
	int cmos_cmd, inc, i;

	int current_value = brightness_get(NULL);



	value &= 7;

	if (value > 7)

		return -EINVAL;



	cmos_cmd = value > current_value ? TP_CMOS_BRIGHTNESS_UP : TP_CMOS_BRIGHTNESS_DOWN;

	cmos_cmd = value > current_value ?

			TP_CMOS_BRIGHTNESS_UP :

			TP_CMOS_BRIGHTNESS_DOWN;

	inc = value > current_value ? 1 : -1;



	for (i = current_value; i != value; i += inc) {

		if (issue_thinkpad_cmos_command(cmos_cmd))

		if ((brightness_mode & 2) &&

		    issue_thinkpad_cmos_command(cmos_cmd))

			return -EIO;

		if (!acpi_ec_write(brightness_offset, i + inc))

		if ((brightness_mode & 1) &&

		    !acpi_ec_write(brightness_offset, i + inc))

			return -EIO;

	}
@@ -4485,6 +4526,9 @@ module_param(force_load, bool, 0); 
static int fan_control_allowed;

module_param_named(fan_control, fan_control_allowed, bool, 0);



static int brightness_mode;

module_param_named(brightness_mode, brightness_mode, int, 0);



#define IBM_PARAM(feature) \

	module_param_call(feature, set_ibm_param, NULL, NULL, 0)

drivers/misc/thinkpad_acpi.h

+7 −0
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ 
#include <linux/list.h>

#include <linux/mutex.h>



#include <linux/nvram.h>

#include <linux/proc_fs.h>

#include <linux/sysfs.h>

#include <linux/backlight.h>
@@ -80,6 +81,11 @@ 
#define TP_CMOS_BRIGHTNESS_UP	4

#define TP_CMOS_BRIGHTNESS_DOWN	5



/* ThinkPad CMOS NVRAM constants */

#define TP_NVRAM_ADDR_BRIGHTNESS       0x5e

#define TP_NVRAM_MASK_LEVEL_BRIGHTNESS 0x07

#define TP_NVRAM_POS_LEVEL_BRIGHTNESS 0



#define onoff(status,bit) ((status) & (1 << (bit)) ? "on" : "off")

#define enabled(status,bit) ((status) & (1 << (bit)) ? "enabled" : "disabled")

#define strlencmp(a,b) (strncmp((a), (b), strlen(b)))
@@ -323,6 +329,7 @@ static int bluetooth_write(char *buf); 


static struct backlight_device *ibm_backlight_device;

static int brightness_offset = 0x31;

static int brightness_mode;



static int brightness_init(struct ibm_init_struct *iibm);

static void brightness_exit(void);