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SubjectRe: [PATCH v2 3/3] ACPI / video: Do not register backlight if win8 and native interface exists
Date
On Tue, 17 Sep 2013, Aaron Lu <aaron.lu@intel.com> 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.
>
> This patch is an evolution from previous work done by Matthew Garrett,
> Chun-Yi Lee, Seth Forshee and Rafael J. Wysocki.
>
> Signed-off-by: Aaron Lu <aaron.lu@intel.com>
> ---
> drivers/acpi/internal.h | 5 ++---
> drivers/acpi/video.c | 27 +++++----------------------
> drivers/acpi/video_detect.c | 14 ++++++++++++--
> 3 files changed, 19 insertions(+), 27 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 5ad5a71..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;
> @@ -1677,23 +1677,6 @@ static int acpi_video_bus_unregister_backlight(struct acpi_video_bus *video)
> return error;
> }
>
> -int acpi_video_unregister_backlight(void)
> -{
> - struct acpi_video_bus *video;
> - int error = 0;
> -
> - mutex_lock(&video_list_lock);
> - list_for_each_entry(video, &video_bus_head, entry) {
> - error = acpi_video_bus_unregister_backlight(video);
> - if (error)
> - break;
> - }
> - mutex_unlock(&video_list_lock);
> -
> - return error;
> -}
> -EXPORT_SYMBOL(acpi_video_unregister_backlight);

You add this in patch 2/3 only to remove it again in 3/3?

> -
> static void acpi_video_dev_add_notify_handler(struct acpi_video_device *device)
> {
> acpi_status status;
> 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;
> + return acpi_video_backlight_support();
> +}

IIUC this expects the raw backlight device to have been registered prior
to calling acpi_video_register(). This only works for i915 which calls
acpi_video_register() itself.


BR,
Jani.



> +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.
> --
> 1.8.4.12.g2ea3df6
>

--
Jani Nikula, Intel Open Source Technology Center


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