acer-wmi: add quirk table for video backlight vendor mode

There have some acer laptop have broken _BCM implemenation, the AML
code wrote value to EC register but firmware didn't change brighenss.

Fortunately, the brightness control works on those machines with
vendor mode. So, add quirk table for video backlight vendor mode
and unregister acpi video interface on those machines.

Tested on Acer TravelMate 4750

Cc: Carlos Corbacho <carlos@strangeworlds.co.uk>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: Dmitry Torokhov <dtor@mail.ru>
Cc: Corentin Chary <corentincj@iksaif.net>
Cc: Thomas Renninger <trenn@suse.de>
Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

2 files changed, 31 insertions, 2 deletions

diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index c5b4bfed7bb4..2a262f5c5c0c 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -26,6 +26,10 @@ config ACER_WMI
         depends on RFKILL || RFKILL = n
         depends on ACPI_WMI
         select INPUT_SPARSEKMAP
+        # Acer WMI depends on ACPI_VIDEO when ACPI is enabled
+        # but for select to work, need to select ACPI_VIDEO's dependencies, ick
+        select VIDEO_OUTPUT_CONTROL if ACPI
+        select ACPI_VIDEO if ACPI
         ---help---
           This is a driver for newer Acer (and Wistron) laptops. It adds
           wireless radio and bluetooth control, and on some laptops,
diff --git a/drivers/platform/x86/acer-wmi.c b/drivers/platform/x86/acer-wmi.c
index b253e219297e..c1a3fd8e1243 100644
--- a/drivers/platform/x86/acer-wmi.c
+++ b/drivers/platform/x86/acer-wmi.c
@@ -43,6 +43,7 @@
 #include <linux/input/sparse-keymap.h>
 
 #include <acpi/acpi_drivers.h>
+#include <acpi/video.h>
 
 MODULE_AUTHOR("Carlos Corbacho");
 MODULE_DESCRIPTION("Acer Laptop WMI Extras Driver");
@@ -506,6 +507,25 @@ static struct dmi_system_id acer_quirks[] = {
         {}
 };
 
+static int video_set_backlight_video_vendor(const struct dmi_system_id *d)
+{
+        interface->capability &= ~ACER_CAP_BRIGHTNESS;
+        pr_info("Brightness must be controlled by generic video driver\n");
+        return 0;
+}
+
+static const struct dmi_system_id video_vendor_dmi_table[] = {
+        {
+                .callback = video_set_backlight_video_vendor,
+                .ident = "Acer TravelMate 4750",
+                .matches = {
+                        DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+                        DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 4750"),
+                },
+        },
+        {}
+};
+
 /* Find which quirks are needed for a particular vendor/ model pair */
 static void find_quirks(void)
 {
@@ -2017,8 +2037,13 @@ static int __init acer_wmi_init(void)
         set_quirks();
 
         if (acpi_video_backlight_support()) {
-                interface->capability &= ~ACER_CAP_BRIGHTNESS;
-                pr_info("Brightness must be controlled by generic video driver\n");
+                if (dmi_check_system(video_vendor_dmi_table)) {
+                        acpi_video_unregister();
+                } else {
+                        interface->capability &= ~ACER_CAP_BRIGHTNESS;
+                        pr_info("Brightness must be controlled by "
+                                "acpi video driver\n");
+                }
         }
 
         if (wmi_has_guid(WMID_GUID3)) {