platform/x86: toshiba_acpi: Stop using acpi_video_set_dmi_backlight_type()

acpi_video_set_dmi_backlight_type() is troublesome because it may end up
getting called after other backlight drivers have already called
acpi_video_get_backlight_type() resulting in the other drivers
already being registered even though they should not.

In case of the acpi_video backlight, acpi_video_set_dmi_backlight_type()
actually calls acpi_video_unregister_backlight() since that is often
probed earlier, leading to userspace seeing the acpi_video0 class
device being briefly available, leading to races in userspace where
udev probe-rules try to access the device and it is already gone.

In case of toshiba_acpi there are no DMI quirks to move to
acpi/video_detect.c, but it also (ab)uses it for transflective
displays. Adding transflective display support to video_detect.c would
be quite involved. But luckily there are only 2 known models with
a transflective display, so we can just add DMI quirks for those.
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/acpi/video_detect.c

@@ -190,6 +190,25 @@ static const struct dmi_system_id video_detect_dmi_table[] = {
 		},
 	},
 
+	/*
+	 * Toshiba models with Transflective display, these need to use
+	 * the toshiba_acpi vendor driver for proper Transflective handling.
+	 */
+	{
+	 .callback = video_detect_force_vendor,
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "PORTEGE R500"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "PORTEGE R600"),
+		},
+	},
+
 	/*
 	 * These models have a working acpi_video backlight control, and using
 	 * native backlight causes a regression where backlight does not work

drivers/platform/x86/toshiba_acpi.c

@@ -271,14 +271,6 @@ static const struct key_entry toshiba_acpi_alt_keymap[] = {
 	{ KE_END, 0 },
 };
 
-/*
- * List of models which have a broken acpi-video backlight interface and thus
- * need to use the toshiba (vendor) interface instead.
- */
-static const struct dmi_system_id toshiba_vendor_backlight_dmi[] = {
-	{}
-};
-
 /*
  * Utility
  */
@@ -2881,14 +2873,6 @@ static int toshiba_acpi_setup_backlight(struct toshiba_acpi_dev *dev)
 		return 0;
 	}
 
-	/*
-	 * Tell acpi-video-detect code to prefer vendor backlight on all
-	 * systems with transflective backlight and on dmi matched systems.
-	 */
-	if (dev->tr_backlight_supported ||
-	    dmi_check_system(toshiba_vendor_backlight_dmi))
-		acpi_video_set_dmi_backlight_type(acpi_backlight_vendor);
-
 	if (acpi_video_get_backlight_type() != acpi_backlight_vendor)
 		return 0;