On 10/10/2013 08:29 AM, Rafael J. Wysocki wrote:
> On Tuesday, October 08, 2013 02:40:00 PM Aaron Lu wrote:
>> According to Matthew Garrett, "Windows 8 leaves backlight control up
>> to individual graphics drivers rather than making ACPI calls itself.
>> There's plenty of evidence to suggest that the Intel driver for
>> Windows [8] doesn't use the ACPI interface, including the fact that
>> it's broken on a bunch of machines when the OS claims to support
>> Windows 8. The simplest thing to do appears to be to disable the
>> ACPI backlight interface on these systems".
>>
>> So for Win8 systems, if there is native backlight control interface
>> registered by GPU driver, ACPI video will not register its own. For
>> users who prefer to keep ACPI video's backlight interface, the existing
>> kernel cmdline option acpi_backlight=video can be used.
>>
>> Signed-off-by: Aaron Lu <aaron...@intel.com>
>> Tested-by: Igor Gnatenko <i.gnatenko.br...@gmail.com>
>> Tested-by: Yves-Alexis Perez <cor...@debian.org>
>> Tested-by: Mika Westerberg <mika.westerb...@linux.intel.com>
>> ---
>> drivers/acpi/internal.h | 5 ++---
>> drivers/acpi/video.c | 10 +++++-----
>> drivers/acpi/video_detect.c | 14 ++++++++++++--
>> 3 files changed, 19 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
>> index 20f4233..453ae8d 100644
>> --- a/drivers/acpi/internal.h
>> +++ b/drivers/acpi/internal.h
>> @@ -169,9 +169,8 @@ int acpi_create_platform_device(struct acpi_device *adev,
>> Video
>>
>> -------------------------------------------------------------------------- */
>> #if defined(CONFIG_ACPI_VIDEO) || defined(CONFIG_ACPI_VIDEO_MODULE)
>> -bool acpi_video_backlight_quirks(void);
>> -#else
>> -static inline bool acpi_video_backlight_quirks(void) { return false; }
>> +bool acpi_osi_is_win8(void);
>> +bool acpi_video_verify_backlight_support(void);
>> #endif
>>
>> #endif /* _ACPI_INTERNAL_H_ */
>> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
>> index 3bd1eaa..343db59 100644
>> --- a/drivers/acpi/video.c
>> +++ b/drivers/acpi/video.c
>> @@ -1256,8 +1256,8 @@ acpi_video_switch_brightness(struct acpi_video_device
>> *device, int event)
>> unsigned long long level_current, level_next;
>> int result = -EINVAL;
>>
>> - /* no warning message if acpi_backlight=vendor is used */
>> - if (!acpi_video_backlight_support())
>> + /* no warning message if acpi_backlight=vendor or a quirk is used */
>> + if (!acpi_video_verify_backlight_support())
>> return 0;
>>
>> if (!device->brightness)
>> @@ -1386,13 +1386,13 @@ acpi_video_bus_get_devices(struct acpi_video_bus
>> *video,
>> static int acpi_video_bus_start_devices(struct acpi_video_bus *video)
>> {
>> return acpi_video_bus_DOS(video, 0,
>> - acpi_video_backlight_quirks() ? 1 : 0);
>> + acpi_osi_is_win8() ? 1 : 0);
>> }
>>
>> static int acpi_video_bus_stop_devices(struct acpi_video_bus *video)
>> {
>> return acpi_video_bus_DOS(video, 0,
>> - acpi_video_backlight_quirks() ? 0 : 1);
>> + acpi_osi_is_win8() ? 0 : 1);
>> }
>>
>> static void acpi_video_bus_notify(struct acpi_device *device, u32 event)
>> @@ -1558,7 +1558,7 @@ acpi_video_bus_match(acpi_handle handle, u32 level,
>> void *context,
>>
>> static void acpi_video_dev_register_backlight(struct acpi_video_device
>> *device)
>> {
>> - if (acpi_video_backlight_support()) {
>> + if (acpi_video_verify_backlight_support()) {
>> struct backlight_properties props;
>> struct pci_dev *pdev;
>> acpi_handle acpi_parent;
>> diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
>> index 940edbf..23d7d26 100644
>> --- a/drivers/acpi/video_detect.c
>> +++ b/drivers/acpi/video_detect.c
>> @@ -37,6 +37,7 @@
>> #include <linux/acpi.h>
>> #include <linux/dmi.h>
>> #include <linux/pci.h>
>> +#include <linux/backlight.h>
>>
>> #include "internal.h"
>>
>> @@ -233,11 +234,11 @@ static void acpi_video_caps_check(void)
>> acpi_video_get_capabilities(NULL);
>> }
>>
>> -bool acpi_video_backlight_quirks(void)
>> +bool acpi_osi_is_win8(void)
>> {
>> return acpi_gbl_osi_data >= ACPI_OSI_WIN_8;
>> }
>> -EXPORT_SYMBOL(acpi_video_backlight_quirks);
>> +EXPORT_SYMBOL(acpi_osi_is_win8);
>>
>> /* Promote the vendor interface instead of the generic video module.
>> * This function allow DMI blacklists to be implemented by externals
>> @@ -283,6 +284,15 @@ int acpi_video_backlight_support(void)
>> }
>> EXPORT_SYMBOL(acpi_video_backlight_support);
>>
>> +bool acpi_video_verify_backlight_support(void)
>> +{
>> + if (!(acpi_video_support & ACPI_VIDEO_BACKLIGHT_FORCE_VIDEO) &&
>> + acpi_osi_is_win8() && backlight_device_registered(BACKLIGHT_RAW))
>> + return false;
>
> If I'm not mistaken, this will introduce a regression for the people who have
> problems with the native i915 backlight on Win8-compatible systems. I'd
> prefer
> to avoid that at this point.
>
OK, I see.
Then I'm afraid a new kernel command line option is needed, something
like video.use_native_backlight and set it to false by default, then
for people who need to avoid the ACPI video backlight interface, they
can add video.use_native_backlight=true to kernel cmdline.
One thing I need to mention is, with the new cmdline option, users will
need to manually add a kernel cmdline option to make backlight work on
their systems, while they can already make backlight work by modifying
xorg.conf to specify using intel_backlight interface, so it doesn't seem
this patchset will be very useful then...
Thanks,
Aaron
>> + return acpi_video_backlight_support();
>> +}
>> +EXPORT_SYMBOL(acpi_video_verify_backlight_support);
>> +
>> /*
>> * Use acpi_backlight=vendor/video to force that backlight switching
>> * is processed by vendor specific acpi drivers or video.ko driver.
>
> Thanks!
>
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