ACPI / video: ignore BIOS initial backlight value for HP m4

commit fedbe9bc upstream.

On HP m4 lapops, BIOS reports minimum backlight on boot and
causes backlight to dim completely. This ignores the initial backlight
values and set to max brightness.

References: https://bugs.launchpad.net/bugs/1184501Signed-off-by: Alex Hung <alex.hung@canonical.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/acpi/video.c

@@ -463,6 +463,14 @@ static struct dmi_system_id video_dmi_table[] __initdata = {
 		DMI_MATCH(DMI_PRODUCT_NAME, "HP 1000 Notebook PC"),
 		},
 	},
+	{
+	 .callback = video_ignore_initial_backlight,
+	 .ident = "HP Pavilion m4",
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Hewlett-Packard"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "HP Pavilion m4 Notebook PC"),
+		},
+	},
 	{}
 };