[PATCH] ACPI: Ignore _BQC object when registering backlight device

[PATCH] ACPI: Ignore _BQC object when registering backlight device

[Zhao Yakui]

Subject: ACPI: Ignore _BQC object when registering backlight device
>From : Zhao Yakui <yakui.zhao@intel.com>

According to acpi spec , the objects of  _BCL and _BCM are required if
integrated LCD is present and supports brightness level .The _BQC is
the optional object. So the _BQC object is ignored when the backlight device
is registered in ACPI video driver.

http://bugzilla.kernel.org/show_bug.cgi?id=10206

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Zhang Rui  <rui.zhang@intel.com>

---
 drivers/acpi/video.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/drivers/acpi/video.c
===================================================================
--- linux-2.6.orig/drivers/acpi/video.c
+++ linux-2.6/drivers/acpi/video.c
@@ -713,7 +713,7 @@ static void acpi_video_device_find_cap(s
 
 	kfree(obj);
 
-	if (device->cap._BCL && device->cap._BCM && device->cap._BQC && max_level > 0){
+	if (device->cap._BCL && device->cap._BCM && max_level > 0) {
 		int result;
 		static int count = 0;
 		char *name;

[PATCH] ACPI: Ignore _BQC object when registering backlight device

[Zhao Yakui]

Subject: ACPI: Ignore _BQC object when registering backlight device
>From : Zhao Yakui <yakui.zhao@intel.com>

According to acpi spec , the objectes of  _BCL and _BCM are required if
integrated LCD is present and supports brightness level and the _BQC is
the optional object. So the _BQC object will be ignored when the backlight 
device is registered.
At the same time when there is no _BQC object, the current brightness will be
set to the maximum.

http://bugzilla.kernel.org/show_bug.cgi?id=10206

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Zhang Rui  <rui.zhang@intel.com>

---
 drivers/acpi/video.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

Index: linux-2.6/drivers/acpi/video.c
===================================================================
--- linux-2.6.orig/drivers/acpi/video.c
+++ linux-2.6/drivers/acpi/video.c
@@ -720,7 +720,7 @@ static void acpi_video_device_find_cap(s
 
 	kfree(obj);
 
-	if (device->cap._BCL && device->cap._BCM && device->cap._BQC && max_level > 0){
+	if (device->cap._BCL && device->cap._BCM && max_level > 0) {
 		int result;
 		static int count = 0;
 		char *name;
@@ -732,7 +732,17 @@ static void acpi_video_device_find_cap(s
 		device->backlight = backlight_device_register(name,
 			NULL, device, &acpi_backlight_ops);
 		device->backlight->props.max_brightness = device->brightness->count-3;
-		device->backlight->props.brightness = acpi_video_get_brightness(device->backlight);
+		/*
+		 * If there exists the _BQC object, the _BQC object will be
+		 * called to get the current backlight brightness. Otherwise
+		 * the brightness will be set to the maximum.
+		 */
+		if (device->cap._BQC)
+			device->backlight->props.brightness =
+				acpi_video_get_brightness(device->backlight);
+		else
+			device->backlight->props.brightness =
+				device->backlight->props.max_brightness;
 		backlight_update_status(device->backlight);
 		kfree(name);
 

[PATCH] ACPI: Ignore _BQC object when registering backlight device

[Zhao Yakui]

>From : Zhao Yakui <yakui.zhao@intel.com>

According to acpi spec , the objectes of  _BCL and _BCM are required if
integrated LCD is present and supports brightness level and the _BQC is
the optional object. So the _BQC object will be ignored when the backlight 
device is registered.
At the same time when there is no _BQC object, the current brightness will be
set to the maximum.

http://bugzilla.kernel.org/show_bug.cgi?id=10206

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Zhang Rui  <rui.zhang@intel.com>

---
 drivers/acpi/video.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

Index: linux-2.6/drivers/acpi/video.c
===================================================================
--- linux-2.6.orig/drivers/acpi/video.c
+++ linux-2.6/drivers/acpi/video.c
@@ -741,7 +741,7 @@ static void acpi_video_device_find_cap(s
 
 	max_level = acpi_video_init_brightness(device);
 
-	if (device->cap._BCL && device->cap._BCM && device->cap._BQC && max_level > 0){
+	if (device->cap._BCL && device->cap._BCM && max_level > 0) {
 		int result;
 		static int count = 0;
 		char *name;
@@ -753,7 +753,17 @@ static void acpi_video_device_find_cap(s
 		device->backlight = backlight_device_register(name,
 			NULL, device, &acpi_backlight_ops);
 		device->backlight->props.max_brightness = device->brightness->count-3;
-		device->backlight->props.brightness = acpi_video_get_brightness(device->backlight);
+		/*
+		 * If there exists the _BQC object, the _BQC object will be
+		 * called to get the current backlight brightness. Otherwise
+		 * the brightness will be set to the maximum.
+		 */
+		if (device->cap._BQC)
+			device->backlight->props.brightness =
+				acpi_video_get_brightness(device->backlight);
+		else
+			device->backlight->props.brightness =
+				device->backlight->props.max_brightness;
 		backlight_update_status(device->backlight);
 		kfree(name);
 

Re: [PATCH] ACPI: Ignore _BQC object when registering backlight device

[Andi Kleen]

Zhao Yakui wrote:
>>From : Zhao Yakui <yakui.zhao@intel.com>
> 
> According to acpi spec , the objectes of  _BCL and _BCM are required if
> integrated LCD is present and supports brightness level and the _BQC is
> the optional object. So the _BQC object will be ignored when the backlight 
> device is registered.
> At the same time when there is no _BQC object, the current brightness will be
> set to the maximum.
> 
> http://bugzilla.kernel.org/show_bug.cgi?id=10206


Hmm, but the original patch was reverted. How is this patch better
than the patch that was reverted by Linus?

-Andi

Re: [PATCH] ACPI: Ignore _BQC object when registering backlight device

[Matthew Garrett]

On Thu, Jul 17, 2008 at 02:44:54PM +0200, Andi Kleen wrote:

> Hmm, but the original patch was reverted. How is this patch better
> than the patch that was reverted by Linus?

The initial patch would have resulted in the screen brightness being set 
to minimum (which may be off on some hardware). The new one sets it to 
maximum brightness if it's not possible to determine the current 
brightness.

-- 
Matthew Garrett | mjg59@srcf.ucam.org