Still use ACPI backlight control if _DOS doesn't exist

Still use ACPI backlight control if _DOS doesn't exist

[Dave Airlie]

This is a regression introduced by commit
ea9f8856bd6d4ed45885b06a338f7362cd6c60e5

https://bugzilla.kernel.org/show_bug.cgi?id=43168

Some platforms don't have _DOS control method, but the ACPI
backlight still works.
We do not want to lose the backlight control ability on these platforms.

[airlied: this is breaking nouveau really badly on 3.4 and after and there is
no movement on sending it upstream, so please apply]

Cc: Igor Murzov <intergalactic.anonymous@gmail.com>
Cc: stable@vger.kernel.org
Cc: len.brown@intel.com
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
---
 drivers/acpi/video.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

Index: rtd3/drivers/acpi/video.c
===================================================================
--- rtd3.orig/drivers/acpi/video.c
+++ rtd3/drivers/acpi/video.c
@@ -565,8 +565,14 @@ acpi_video_bus_DOS(struct acpi_video_bus
 	video->dos_setting = arg0.integer.value;
 	status = acpi_evaluate_object(video->device->handle, "_DOS",
 		&args, NULL);
-	if (ACPI_FAILURE(status))
-		return -EIO;
+	if (ACPI_FAILURE(status)) {
+		/*
+		 * some platforms don't have _DOS, but the ACPI
+		 * backlight control still works
+		 */
+		ACPI_DEBUG_PRINT((ACPI_DB_INFO, "No _DOS\n"));
+		return 0;
+	}
 
 	return 0;
 }

Re: Still use ACPI backlight control if _DOS doesn't exist

[Zhang Rui]

Hi, Dave,

How about this one, which I think is better? :)
http://marc.info/?l=linux-acpi&m=134015703925079&w=2

can you give it a try?

thanks,
rui

On 一, 2012-06-25 at 12:38 +0100, Dave Airlie wrote:
> This is a regression introduced by commit
> ea9f8856bd6d4ed45885b06a338f7362cd6c60e5
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=43168
> 
> Some platforms don't have _DOS control method, but the ACPI
> backlight still works.
> We do not want to lose the backlight control ability on these platforms.
> 
> [airlied: this is breaking nouveau really badly on 3.4 and after and there is
> no movement on sending it upstream, so please apply]
> 
> Cc: Igor Murzov <intergalactic.anonymous@gmail.com>
> Cc: stable@vger.kernel.org
> Cc: len.brown@intel.com
> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> ---
>  drivers/acpi/video.c |   10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> Index: rtd3/drivers/acpi/video.c
> ===================================================================
> --- rtd3.orig/drivers/acpi/video.c
> +++ rtd3/drivers/acpi/video.c
> @@ -565,8 +565,14 @@ acpi_video_bus_DOS(struct acpi_video_bus
>  	video->dos_setting = arg0.integer.value;
>  	status = acpi_evaluate_object(video->device->handle, "_DOS",
>  		&args, NULL);
> -	if (ACPI_FAILURE(status))
> -		return -EIO;
> +	if (ACPI_FAILURE(status)) {
> +		/*
> +		 * some platforms don't have _DOS, but the ACPI
> +		 * backlight control still works
> +		 */
> +		ACPI_DEBUG_PRINT((ACPI_DB_INFO, "No _DOS\n"));
> +		return 0;
> +	}
>  
>  	return 0;
>  }