ACPI: video: Ignore BIOS initial backlight value for HP 250 G1

On HP 250 G1 laptops, BIOS reports minimum backlight on boot and causes backlight to dim completely. This ignores the initial backlight values and set to max brightness.

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=63111

---
 drivers/acpi/video.c | 8 ++++++++
 1 file changed, 8 insertions(+)

index 3270d3c..6456466 100644
@@ -490,6 +490,14 @@ static struct dmi_system_id video_dmi_table[] __initdata = {
 		DMI_MATCH(DMI_PRODUCT_NAME, "HP Pavilion m4 Notebook PC"),
 		},
 	},
+	{
+	 .callback = video_ignore_initial_backlight,
+	 .ident = "HP 250 G1",
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Hewlett-Packard"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "HP 250 G1 Notebook PC"),
+		},
+	},
 	{}
 };
 

According to the acpidump:

The ASL code initialize initial brightness level to 100, but only for OS that is pre-vista. Don't know why it does this...

Method (_INI, 0, NotSerialized) // _INI: Initialize

{
	If (LLess (OSYS, 0x07D6))
	{
		Store (0x64, BRTL)
	}
	... ...
}

Method (_BQC, 0, NotSerialized) // _BQC: Brightness Query Current {
Return (BRTL)
}

Since it is not initialized in _INI(as we report to firmware we are 'Windows 2012'), the video module was told by _BQC the initial brightness level is 0 and then set backlight level to 0 and leads to a black screen after boot up.

The patch looks good to me.

Thanks,
Aaron