ACPI: video: Do not export a non working backlight interface on MSI M…

…S-7721 boards

Despite our heuristics to not wrongly export a non working ACPI backlight
interface on desktop machines, we still end up exporting one on desktops
using a motherboard from the MSI MS-7721 series.

I've looked at improving the heuristics, but in this case a quirk seems
to be the only way to solve this.

While at it also add a comment to separate the video_detect_force_none
entries in the video_detect_dmi_table from other type of entries, as we
already do for the other entry types.

Cc: All applicable <stable@vger.kernel.org>
BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1783786
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/video_detect.c

@@ -352,6 +352,11 @@ static const struct dmi_system_id video_detect_dmi_table[] = {
 		DMI_MATCH(DMI_PRODUCT_NAME, "Precision 7510"),
 		},
 	},
+
+	/*
+	 * Desktops which falsely report a backlight and which our heuristics
+	 * for this do not catch.
+	 */
 	{
 	 .callback = video_detect_force_none,
 	 .ident = "Dell OptiPlex 9020M",
@@ -360,6 +365,14 @@ static const struct dmi_system_id video_detect_dmi_table[] = {
 		DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 9020M"),
 		},
 	},
+	{
+	 .callback = video_detect_force_none,
+	 .ident = "MSI MS-7721",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "MSI"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "MS-7721"),
+		},
+	},
 	{ },
 };