On 03/14/2013 06:34 PM, Danny Baumann wrote:
> In particular, this fixes brightness control initialization for all
> devices that return index values from _BQC and don't happen to have the
> initial index set by the BIOS in their _BCL table. One example for that
> is the Dell Inspiron 15R SE (model number 7520).
>
> What happened for those devices is that acpi_init_brightness queried the
> initial brightness by calling acpi_video_device_lcd_get_level_current.
> This called _BQC, which returned e.g. 13. As _BQC_use_index isn't
> determined at this point (and thus has its initial value of 0), the
> index isn't converted into the actual level. As '13' isn't present in
> the _BCL list, *level is later overwritten with brightness->curr, which
> was initialized to max_level (100) before. Later in
> acpi_init_brightness, level_old (with the value 100) is used as an index
> into the _BCL table, which causes a value outside of the actual table to
> be used as input into acpi_video_device_lcd_set_level(). Depending on
> the (undefined) value of that location, this call will fail, causing the
> brightness control for the device in question not to be enabled.
>
> Fix that by returning the raw value returned by the _BQC call in the
> initialization case.
You missed Signed-off-by tag here.
Other than that, Reviewed-by: Aaron Lu <aaron.lu@xxxxxxxxx>.
Thanks,
Aaron
> ---
> drivers/acpi/video.c | 29 ++++++++++++++++++-----------
> 1 file changed, 18 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
> index 313f959..ef85574 100644
> --- a/drivers/acpi/video.c
> +++ b/drivers/acpi/video.c
> @@ -463,6 +463,15 @@ acpi_video_device_lcd_get_level_current(struct acpi_video_device *device,
> status = acpi_evaluate_integer(device->dev->handle, buf,
> NULL, level);
> if (ACPI_SUCCESS(status)) {
> + if (init) {
> + /*
> + * At init time we don't yet know whether the
> + * value is indexed or not. Don't mess with it
> + * until we have determined how to handle it.
> + */
> + return 0;
> + }
> +
> if (device->brightness->flags._BQC_use_index) {
> if (device->brightness->flags._BCL_reversed)
> *level = device->brightness->count
> @@ -476,16 +485,14 @@ acpi_video_device_lcd_get_level_current(struct acpi_video_device *device,
> device->brightness->curr = *level;
> return 0;
> }
> - if (!init) {
> - /*
> - * BQC returned an invalid level.
> - * Stop using it.
> - */
> - ACPI_WARNING((AE_INFO,
> - "%s returned an invalid level",
> - buf));
> - device->cap._BQC = device->cap._BCQ = 0;
> - }
> + /*
> + * BQC returned an invalid level.
> + * Stop using it.
> + */
> + ACPI_WARNING((AE_INFO,
> + "%s returned an invalid level",
> + buf));
> + device->cap._BQC = device->cap._BCQ = 0;
> } else {
> /* Fixme:
> * should we return an error or ignore this failure?
> @@ -714,7 +721,7 @@ acpi_video_init_brightness(struct acpi_video_device *device)
> if (result)
> goto out_free_levels;
>
> - result = acpi_video_device_lcd_get_level_current(device, &level, 0);
> + result = acpi_video_device_lcd_get_level_current(device, &level, 1);
> if (result)
> goto out_free_levels;
>
>
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