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author | Hans de Goede <hdegoede@redhat.com> | 2014-05-17 12:48:01 +0400 |
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committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2014-05-20 15:41:42 +0400 |
commit | 1b7f37e1276bee9043d35a4b39ef2f43d3b2e133 (patch) | |
tree | 8e46c57e24b457cfd5c1706683cef1b6f1a00c40 /drivers/acpi | |
parent | 99678ed73a50d2df8b5f3c801e29e9b7a3e5aa85 (diff) | |
download | linux-1b7f37e1276bee9043d35a4b39ef2f43d3b2e133.tar.xz |
ACPI / video: Add an acpi_video_unregister_backlight function
Add an acpi_video_unregister_backlight function, which only unregisters
the backlight device, and leaves the acpi_notifier in place. Some acpi_vendor
driver need this as they don't want the acpi_video# backlight device, but do
need the acpi-video driver for hotkey handling.
Chances are that this new acpi_video_unregister_backlight() is actually
what existing acpi_vendor drivers have wanted all along. Currently acpi_vendor
drivers which want to disable the acpi_video# backlight device, make 2 calls:
acpi_video_dmi_promote_vendor();
acpi_video_unregister();
The intention here is to make things independent of when acpi_video_register()
gets called. As acpi_video_register() will get called on acpi-video load time
on non intel gfx machines, while it gets called on i915 load time on intel
gfx machines.
This leads to the following 2 interesting scenarios:
a) intel gfx:
1) acpi-video module gets loaded (as it is a dependency of acpi_vendor
and i915)
2) acpi-video does NOT call acpi_video_register()
3) acpi_vendor loads (lets assume it loads before i915), calls
acpi_video_dmi_promote_vendor(); which sets
ACPI_VIDEO_BACKLIGHT_DMI_VENDOR
4) calls acpi_video_unregister -> not registered, nop
5) i915 loads, calls acpi_video_register
6) acpi_video_register registers the acpi_notifier for the hotkeys,
does NOT register a backlight device because of
ACPI_VIDEO_BACKLIGHT_DMI_VENDOR
b) non intel gfx
1) acpi-video module gets loaded (as it is a dependency acpi_vendor)
2) acpi-video calls acpi_video_register()
3) acpi_video_register registers the acpi_notifier for the hotkeys,
and a backlight device
4) acpi_vendor loads, calls acpi_video_dmi_promote_vendor()
5) calls acpi_video_unregister, this unregisters BOTH the acpi_notifier
for the hotkeys AND the backlight device
So here we have possibly the same acpi_vendor module, making the same calls,
but with different results, in one cases acpi-video does handle hotkeys,
in the other it does not.
Note that the a) scenario turns into b) if we assume the i915 module loads
before the vendor_acpi module, so we also have different behavior depending
on module loading order!
So as said I believe that quite a few existing acpi_vendor modules really
always want the behavior of a), hence this patch adds a new
acpi_video_unregister_backlight() which gives the behavior of a) independent
of module loading order.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/acpi')
-rw-r--r-- | drivers/acpi/video.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c index ff79dff371fd..adbfe39f5454 100644 --- a/drivers/acpi/video.c +++ b/drivers/acpi/video.c @@ -2078,6 +2078,20 @@ void acpi_video_unregister(void) } EXPORT_SYMBOL(acpi_video_unregister); +void acpi_video_unregister_backlight(void) +{ + struct acpi_video_bus *video; + + if (!register_count) + return; + + mutex_lock(&video_list_lock); + list_for_each_entry(video, &video_bus_head, entry) + acpi_video_bus_unregister_backlight(video); + mutex_unlock(&video_list_lock); +} +EXPORT_SYMBOL(acpi_video_unregister_backlight); + /* * This is kind of nasty. Hardware using Intel chipsets may require * the video opregion code to be run first in order to initialise |