[PATCH 1/1] UBUNTU: SAUCE: don't use buggy _BCL/_BCM/_BQC for backlight control

[Stefan Bader]

Andy Whitcroft wrote:
> OriginalAuthor: Zhang Rui <rui.zhang at intel.com>
> Bug: #311716
> 
> [This patch is currently in the acpi-test tree, it is reported to fix
> brightness inversion regressions by our tester.  We expect this to be
> merged and superceeded by an upstream commit.]
> 
> Some BIOSes export buggy _BCL/_BCM/_BQC methods.
> Don't use them for backlight control
> 
> Signed-off-by: Zhang Rui <rui.zhang at intel.com>
> Signed-off-by: Andy Whitcroft <apw at canonical.com>
> ---
>  drivers/acpi/video_detect.c |   83 +++++++++++++++++++++++++++++++++++++++---
>  1 files changed, 77 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
> index 70b1e91..9bf4865 100644
> --- a/drivers/acpi/video_detect.c
> +++ b/drivers/acpi/video_detect.c
> @@ -45,17 +45,88 @@ static long acpi_video_support;
>  static bool acpi_video_caps_checked;
>  
>  static acpi_status
> +acpi_backlight_validate_bcl(acpi_handle handle)
> +{
> +	union acpi_object *obj, *obj2;
> +	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> +	int level_ac = 0, level_battery = 0;
> +	int i, count;
> +	int *levels;
> +	acpi_status status;
> +
> +
> +	status = acpi_evaluate_object(handle, "_BCL", NULL, &buffer);
> +	if (!ACPI_SUCCESS(status))
> +		return status;
> +	obj = (union acpi_object *)buffer.pointer;
> +	if (!obj || (obj->type != ACPI_TYPE_PACKAGE)) {
> +		printk(KERN_ERR PREFIX "Invalid _BCL data\n");
> +		status = AE_BAD_DATA;
> +		goto out;
> +	}
> +
> +	if (obj->package.count < 2) {
> +		status = AE_BAD_DATA;
> +		goto out;
> +	}
> +
> +        levels = kzalloc(obj->package.count * sizeof(*levels), GFP_KERNEL);
> +	if (!levels) {
> +		status = AE_NO_MEMORY;
> +		goto out;
> +	}
> +
> +	for (i = 0, count = 0; i < obj->package.count; i++) {
> +		obj2 = (union acpi_object *)&obj->package.elements[i];
> +		if (obj2->type != ACPI_TYPE_INTEGER) {
> +			printk(KERN_ERR PREFIX "Invalid data\n");
> +			continue;
> +		}
> +		levels[i] = (u32) obj2->integer.value;
> +		count ++;
> +        }
> +
> +        if (count < 2) {
> +		status = AE_BAD_DATA;
> +		goto out_free_levels;
> +	}
> +
> +	for (i = 2, level_ac = levels[0], level_battery = levels[1]; i < count; i ++) {
> +		if (levels[0] == levels[i])
> +			level_ac = 1;
> +		if (levels[1] == levels[i])
> +			level_battery = 1;
> +	}
> +
> +	if (!level_ac || !level_battery) {
> +		printk(KERN_ERR PREFIX "Invalid _BCL package\n");
> +		status = AE_BAD_DATA;
> +		goto out_free_levels;
> +	}
> +
> +        ACPI_DEBUG_PRINT((ACPI_DB_INFO, "found %d brightness levels\n", count));
> +
> +out_free_levels:
> +	kfree(levels);
> +out:
> +        kfree(obj);
> +        return status;
> +}
> +
> +static acpi_status
>  acpi_backlight_cap_match(acpi_handle handle, u32 level, void *context,
>  			  void **retyurn_value)
>  {
>  	long *cap = context;
> -	acpi_handle h_dummy;
> +	acpi_handle h_dummy1, h_dummy2;
>  
> -	if (ACPI_SUCCESS(acpi_get_handle(handle, "_BCM", &h_dummy)) &&
> -	    ACPI_SUCCESS(acpi_get_handle(handle, "_BCL", &h_dummy))) {
> -		ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Found generic backlight "
> -				  "support\n"));
> -		*cap |= ACPI_VIDEO_BACKLIGHT;
> +	if (ACPI_SUCCESS(acpi_get_handle(handle, "_BCM", &h_dummy1)) &&
> +	    ACPI_SUCCESS(acpi_get_handle(handle, "_BCL", &h_dummy2))) {
> +		if (ACPI_SUCCESS(acpi_backlight_validate_bcl(h_dummy2))) {
> +			ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Found generic backlight "
> +					  "support\n"));
> +			*cap |= ACPI_VIDEO_BACKLIGHT;
> +		}
>  		/* We have backlight support, no need to scan further */
>  		return AE_CTRL_TERMINATE;
>  	}
ACK

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