[PATCH 3/3] ACPI: video: Add backlight=native quirk for Dell OptiPlex 7760 AIO

[Hans de Goede]

Dell All In One (AIO) models released after 2017 may use a backlight
controller board connected to an UART.

In DSDT this uart port will be defined as:

   Name (_HID, "DELL0501")
   Name (_CID, EisaId ("PNP0501")

The Dell OptiPlex 7760 AIO has an ACPI device for one if its UARTs with
the above _HID + _CID. Loading the dell-uart-backlight driver shows that
there actually is a backlight controller board attached to the UART,
which reports a firmware version of "G&MX01-V15".

But the backlight controller board does not actually control the backlight
brightness and the GPU's native backlight control method does work.

Add a quirk to use the GPU's native backlight control method on this model.

Fixes: 484bae9e4d6a ("platform/x86: Add new Dell UART backlight driver")
Closes: https://bugzilla.redhat.com/show_bug.cgi?id=2303936
Cc: stable at vger.kernel.org
Signed-off-by: Hans de Goede <hdegoede at redhat.com>
---
 drivers/acpi/video_detect.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
index e509dcbf3090..674b9db7a1ef 100644
--- a/drivers/acpi/video_detect.c
+++ b/drivers/acpi/video_detect.c
@@ -823,6 +823,21 @@ static const struct dmi_system_id video_detect_dmi_table[] = {
 		},
 	},
 
+	/*
+	 * Dell AIO (All in Ones) which advertise an UART attached backlight
+	 * controller board in their ACPI tables (and may even have one), but
+	 * which need native backlight control nevertheless.
+	 */
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=2303936 */
+	 .callback = video_detect_force_native,
+	 /* Dell OptiPlex 7760 AIO */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 7760 AIO"),
+		},
+	},
+
 	/*
 	 * Models which have nvidia-ec-wmi support, but should not use it.
 	 * Note this indicates a likely firmware bug on these models and should
-- 
2.46.0