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: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/misc/thinkpad_acpi.h b/drivers/misc/thinkpad_acpi.h
index 09b2282fed0b..b7a4a888cc8b 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);