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    SubjectRe: [PATCH 3/3] i915: Don't provide ACPI backlight interface if firmware expects Windows 8
    On 07/07/2013 09:19 PM, Rafael J. Wysocki wrote:
    > OK, the patch is appended. Please have a look and tell me what you think.
    >
    > Thanks,
    > Rafael
    >
    >
    > ---
    > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    > Subject: ACPI / video / i915: Remove ACPI backlight if firmware expects Windows 8
    >
    > 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".
    >
    > There's a problem with that approach, however, because simply
    > avoiding to register the ACPI backlight interface if the firmware
    > calls _OSI for Windows 8 may not work in the following situations:
    > (1) The ACPI backlight interface actually works on the given system
    > and the i915 driver is not loaded (e.g. another graphics driver
    > is used).
    > (2) The ACPI backlight interface doesn't work on the given system,
    > but there is a vendor platform driver that will register its
    > own, equally broken, backlight interface if the ACPI one is not
    > registered in advance.

    The condition thinkpad_acpi checks to decide if it wants to create
    backlight control interface is acpi_video_backlight_support function,
    not that if ACPI video driver has registered previously. I'm sorry if my
    previous words gave you such a conclusion.

    > Therefore we need to keep the ACPI backlight interface registered
    > until the i915 driver is loaded which then will unregister it if
    > the firmware has called _OSI for Windows 8.
    >
    > For this reason, introduce an alternative function for registering
    > ACPI video, acpi_video_register_with_quirks(), that will check
    > whether or not the ACPI video driver has already been registered
    > and whether or not the backlight Windows 8 quirk has to be applied.
    > If the quirk has to be applied, it will block the ACPI backlight
    > support and either unregister the backlight interface if the ACPI
    > video driver has already been registered, or register the ACPI
    > video driver without the backlight interface otherwise. Make
    > the i915 driver use acpi_video_register_with_quirks() instead of
    > acpi_video_register() in i915_driver_load().
    >
    > This change is based on earlier patches from Matthew Garrett,
    > Chun-Yi Lee and Seth Forshee.
    >
    > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    > ---
    > drivers/acpi/video.c | 61 ++++++++++++++++++++++++++++++++++++----
    > drivers/acpi/video_detect.c | 11 +++++++
    > drivers/gpu/drm/i915/i915_dma.c | 2 -
    > include/acpi/video.h | 11 ++++++-
    > include/linux/acpi.h | 6 +++
    > 5 files changed, 84 insertions(+), 7 deletions(-)
    >
    > Index: linux-pm/drivers/acpi/video.c
    > ===================================================================
    > --- linux-pm.orig/drivers/acpi/video.c
    > +++ linux-pm/drivers/acpi/video.c
    > @@ -1854,6 +1854,46 @@ static int acpi_video_bus_remove(struct
    > return 0;
    > }
    >
    > +static acpi_status video_unregister_backlight(acpi_handle handle, u32 lvl,
    > + void *context, void **rv)
    > +{
    > + struct acpi_device *acpi_dev;
    > + struct acpi_video_bus *video;
    > + struct acpi_video_device *dev, *next;
    > +
    > + if (acpi_bus_get_device(handle, &acpi_dev))
    > + return AE_OK;
    > +
    > + if (acpi_match_device_ids(acpi_dev, video_device_ids))
    > + return AE_OK;
    > +
    > + video = acpi_driver_data(acpi_dev);
    > + if (!video)
    > + return AE_OK;
    > +
    > + acpi_video_bus_stop_devices(video);
    > + mutex_lock(&video->device_list_lock);
    > + list_for_each_entry_safe(dev, next, &video->video_device_list, entry) {
    > + if (dev->backlight) {
    > + backlight_device_unregister(dev->backlight);
    > + dev->backlight = NULL;
    > + kfree(dev->brightness->levels);
    > + kfree(dev->brightness);
    > + }
    > + if (dev->cooling_dev) {
    > + sysfs_remove_link(&dev->dev->dev.kobj,
    > + "thermal_cooling");
    > + sysfs_remove_link(&dev->cooling_dev->device.kobj,
    > + "device");
    > + thermal_cooling_device_unregister(dev->cooling_dev);
    > + dev->cooling_dev = NULL;
    > + }
    > + }
    > + mutex_unlock(&video->device_list_lock);
    > + acpi_video_bus_start_devices(video);
    > + return AE_OK;
    > +}
    > +
    > static int __init is_i740(struct pci_dev *dev)
    > {
    > if (dev->device == 0x00D1)
    > @@ -1885,14 +1925,25 @@ static int __init intel_opregion_present
    > return opregion;
    > }
    >
    > -int acpi_video_register(void)
    > +int __acpi_video_register(bool backlight_quirks)
    > {
    > - int result = 0;
    > + bool no_backlight;
    > + int result;
    > +
    > + no_backlight = backlight_quirks ? acpi_video_backlight_quirks() : false;
    > +
    > if (register_count) {
    > /*
    > - * if the function of acpi_video_register is already called,
    > - * don't register the acpi_vide_bus again and return no error.
    > + * If acpi_video_register() has been called already, don't try
    > + * to register acpi_video_bus, but unregister backlight devices
    > + * if no backlight support is requested.
    > */
    > + if (no_backlight)
    > + acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
    > + ACPI_UINT32_MAX,
    > + video_unregister_backlight,
    > + NULL, NULL, NULL);
    > +
    > return 0;
    > }
    >
    > @@ -1908,7 +1959,7 @@ int acpi_video_register(void)
    >
    > return 0;
    > }
    > -EXPORT_SYMBOL(acpi_video_register);
    > +EXPORT_SYMBOL(__acpi_video_register);
    >
    > void acpi_video_unregister(void)
    > {
    > Index: linux-pm/drivers/gpu/drm/i915/i915_dma.c
    > ===================================================================
    > --- linux-pm.orig/drivers/gpu/drm/i915/i915_dma.c
    > +++ linux-pm/drivers/gpu/drm/i915/i915_dma.c
    > @@ -1660,7 +1660,7 @@ int i915_driver_load(struct drm_device *
    > if (INTEL_INFO(dev)->num_pipes) {
    > /* Must be done after probing outputs */
    > intel_opregion_init(dev);
    > - acpi_video_register();
    > + acpi_video_register_with_quirks();
    > }
    >
    > if (IS_GEN5(dev))
    > Index: linux-pm/include/acpi/video.h
    > ===================================================================
    > --- linux-pm.orig/include/acpi/video.h
    > +++ linux-pm/include/acpi/video.h
    > @@ -17,12 +17,21 @@ struct acpi_device;
    > #define ACPI_VIDEO_DISPLAY_LEGACY_TV 0x0200
    >
    > #if (defined CONFIG_ACPI_VIDEO || defined CONFIG_ACPI_VIDEO_MODULE)
    > -extern int acpi_video_register(void);
    > +extern int __acpi_video_register(bool backlight_quirks);
    > +static inline int acpi_video_register(void)
    > +{
    > + return __acpi_video_register(false);
    > +}
    > +static inline int acpi_video_register_with_quirks(void)
    > +{
    > + return __acpi_video_register(true);
    > +}
    > extern void acpi_video_unregister(void);
    > extern int acpi_video_get_edid(struct acpi_device *device, int type,
    > int device_id, void **edid);
    > #else
    > static inline int acpi_video_register(void) { return 0; }
    > +static inline int acpi_video_register_with_quirks(void) { return 0; }
    > static inline void acpi_video_unregister(void) { return; }
    > static inline int acpi_video_get_edid(struct acpi_device *device, int type,
    > int device_id, void **edid)
    > Index: linux-pm/drivers/acpi/video_detect.c
    > ===================================================================
    > --- linux-pm.orig/drivers/acpi/video_detect.c
    > +++ linux-pm/drivers/acpi/video_detect.c
    > @@ -234,6 +234,17 @@ static void acpi_video_caps_check(void)
    > acpi_video_get_capabilities(NULL);
    > }
    >
    > +bool acpi_video_backlight_quirks(void)
    > +{
    > + if (acpi_gbl_osi_data >= ACPI_OSI_WIN_8) {
    > + acpi_video_caps_check();
    > + acpi_video_support |= ACPI_VIDEO_BACKLIGHT_FORCE_VENDOR;

    If the ACPI_VIDEO_BACKLIGHT_FORCE_VENDOR flag is set,
    acpi_video_backlight_support will return 0, thinkpad_acpi will create
    backlight interface for the system, which is not what we want.

    Thanks,
    Aaron

    > + return true;
    > + }
    > + return false;
    > +}
    > +EXPORT_SYMBOL(acpi_video_backlight_quirks);
    > +
    > /* Promote the vendor interface instead of the generic video module.
    > * This function allow DMI blacklists to be implemented by externals
    > * platform drivers instead of putting a big blacklist in video_detect.c
    > Index: linux-pm/include/linux/acpi.h
    > ===================================================================
    > --- linux-pm.orig/include/linux/acpi.h
    > +++ linux-pm/include/linux/acpi.h
    > @@ -196,6 +196,7 @@ extern bool wmi_has_guid(const char *gui
    >
    > extern long acpi_video_get_capabilities(acpi_handle graphics_dev_handle);
    > extern long acpi_is_video_device(acpi_handle handle);
    > +extern bool acpi_video_backlight_quirks(void);
    > extern void acpi_video_dmi_promote_vendor(void);
    > extern void acpi_video_dmi_demote_vendor(void);
    > extern int acpi_video_backlight_support(void);
    > @@ -213,6 +214,11 @@ static inline long acpi_is_video_device(
    > return 0;
    > }
    >
    > +static inline bool acpi_video_backlight_quirks(void)
    > +{
    > + return false;
    > +}
    > +
    > static inline void acpi_video_dmi_promote_vendor(void)
    > {
    > }
    >



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