From 1b7f37e1276bee9043d35a4b39ef2f43d3b2e133 Mon Sep 17 00:00:00 2001 From: Hans de Goede Date: Sat, 17 May 2014 10:48:01 +0200 Subject: 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 Signed-off-by: Rafael J. Wysocki --- drivers/acpi/video.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'drivers/acpi/video.c') 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 -- cgit v1.2.3-59-g8ed1b