ACPI: thinkpad-acpi: allow use of CMOS NVRAM for brightness control

Henrique de Moraes Holschuh
2007-07-14T14:12:08Z

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: Henrique de Moraes Holschuh <hmh-N3TV7GIv+o9fyO9Q7EP/yw@public.gmane.org>
---
Documentation/thinkpad-acpi.txt | 6 ++++
drivers/misc/Kconfig | 1 +
drivers/misc/thinkpad_acpi.c | 62 +++++++++++++++++++++++++++++++++-----
drivers/misc/thinkpad_acpi.h | 7 ++++
4 files changed, 67 insertions(+), 9 deletions(-)

diff --git a/Documentation/thinkpad-acpi.txt b/Documentation/thinkpad-acpi.txt
index c670363..c145bcc 100644
--- a/Documentation/thinkpad-acpi.txt
+++ b/Documentation/thinkpad-acpi.txt
@@ -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:
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 7d92f26..e39cedb 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -141,6 +141,7 @@ 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
diff --git a/drivers/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
index 99500af..5318eb2 100644
--- a/drivers/misc/thinkpad_acpi.c
+++ b/drivers/misc/thinkpad_acpi.c
@@ -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))
- return -EIO;
+ u8 lec = 0, lcmos = 0, level = 0;

- level &= 0x7;
+ 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;
+ }
+
+ 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)

diff --git a/drivers/misc/thinkpad_acpi.h b/drivers/misc/thinkpad_acpi.h
index 09b2282..b7a4a88 100644
--- a/drivers/misc/thinkpad_acpi.h
+++ b/drivers/misc/thinkpad_acpi.h
@@ -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);
--
1.5.2.1