thinkpad-acpi: untangle ACPI/vendor backlight selection

acpi_video_backlight_support() already tells us if ACPI is handling
backlight control through the generic ACPI handle.  It is better to just
trust it.

While at it, adjust down a printk priority, and test earlier for
brightness_enable=0.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index f6f80257addb..1565eefd6fd5 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -1024,6 +1024,10 @@ ThinkPad-specific interface.  The driver will disable its native
 backlight brightness control interface if it detects that the standard
 ACPI interface is available in the ThinkPad.
 
+If you want to use the thinkpad-acpi backlight brightness control
+instead of the generic ACPI video backlight brightness control for some
+reason, you should use the acpi_backlight=vendor kernel parameter.
+
 The brightness_enable module parameter can be used to control whether
 the LCD brightness control feature will be enabled when available.
 brightness_enable=0 forces it to be disabled.  brightness_enable=1