ACPI video: ignore BIOS backlight value for HP dm4

On a HP Pavilion dm4 laptop the BIOS sets minimum backlight on boot,
completely dimming the screen. Ignore this initial value for this
machine.

Signed-off-by: Gustavo Maciel Dias Vieira <gustavo@sagui.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/video.c

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 313f959..f8a28b3 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -447,6 +447,14 @@
 		DMI_MATCH(DMI_PRODUCT_NAME, "HP Folio 13 - 2000 Notebook PC"),
 		},
 	},
+	{
+	 .callback = video_ignore_initial_backlight,
+	 .ident = "HP Pavilion dm4",
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Hewlett-Packard"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "HP Pavilion dm4 Notebook PC"),
+		},
+	},
 	{}
 };