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ACPI: video: Simplify __acpi_video_get_backlight_type()

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Simplify __acpi_video_get_backlight_type() removing a nested if which
makes the flow harder to follow.

This also results in having only 1 exit point with
return acpi_backlight_native instead of 2.

Note this drops the (video_caps & ACPI_VIDEO_BACKLIGHT) check from
the if (acpi_osi_is_win8() && native_available) return native path.
Windows 8's hardware certification requirements include that there must
be ACPI video bus backlight control, so the ACPI_VIDEO_BACKLIGHT check
is redundant.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Hans de Goede 2022-11-14 15:44:58 +01:00 committed by Rafael J. Wysocki
parent f5a6ff923d
commit a5df42521f
1 changed files with 17 additions and 19 deletions
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36
drivers/acpi/video_detect.c
View file

@ -715,6 +715,16 @@ static bool google_cros_ec_present(void)
return acpi_dev_found("GOOG0004") || acpi_dev_found("GOOG000C");
}
/*
* Windows 8 and newer no longer use the ACPI video interface, so it often
* does not work. So on win8+ systems prefer native brightness control.
* Chromebooks should always prefer native backlight control.
*/
static bool prefer_native_over_acpi_video(void)
{
return acpi_osi_is_win8() || google_cros_ec_present();
}
/*
* Determine which type of backlight interface to use on this system,
* First check cmdline, then dmi quirks, then do autodetect.
@ -760,26 +770,14 @@ static enum acpi_backlight_type __acpi_video_get_backlight_type(bool native)
if (apple_gmux_present())
return acpi_backlight_apple_gmux;
/* Chromebooks should always prefer native backlight control. */
if (google_cros_ec_present() && native_available)
return acpi_backlight_native;
/* Use ACPI video if available, except when native should be preferred. */
if ((video_caps & ACPI_VIDEO_BACKLIGHT) &&
!(native_available && prefer_native_over_acpi_video()))
return acpi_backlight_video;
/* On systems with ACPI video use either native or ACPI video. */
if (video_caps & ACPI_VIDEO_BACKLIGHT) {
/*
* Windows 8 and newer no longer use the ACPI video interface,
* so it often does not work. If the ACPI tables are written
* for win8 and native brightness ctl is available, use that.
*
* The native check deliberately is inside the if acpi-video
* block on older devices without acpi-video support native
* is usually not the best choice.
*/
if (acpi_osi_is_win8() && native_available)
return acpi_backlight_native;
else
return acpi_backlight_video;
}
/* Use native if available */
if (native_available && prefer_native_over_acpi_video())
return acpi_backlight_native;
/* No ACPI video (old hw), use vendor specific fw methods. */
return acpi_backlight_vendor;