[PATCH v5] ACPI: video: force native backlight on Dell OptiPlex AIO 7410 35W

[chitranshmandhaniya@gmail.com]

From: Chitransh Mandhaniya <Chitransh_Mandhaniya@dell.com>

The Dell OptiPlex AIO 7410 35W (board 01KP8D) declares DELL0501 in its
ACPI DSDT (status = 0x0F) even though no UART scalar board is physically
present. This causes acpi_video_get_backlight_type() to return
acpi_backlight_dell_uart, which makes i915 skip registering
intel_backlight. The dell-uart-backlight driver then times out talking
to the absent board and the probe fails, leaving the machine with zero
backlight control.

A BIOS update fixes this on some models (e.g. OptiPlex 7420, board
0914RT) by setting DELL0501 _STA to 0, but Dell has not shipped a
corrected BIOS for the 7410 even in the latest release (1.37.0,
2026-05-28).

Add a DMI quirk to force native backlight on this model so that i915
registers intel_backlight and brightness control works out of the box.

Tested on:
  - OptiPlex AIO 7410 35W (01KP8D, BIOS 1.37.0) -- confirmed
    acpi_backlight=native produces working intel_backlight (raw,
    max=96000), DMI quirk has the same effect.
  - OptiPlex AIO 7420 35W (0914RT, BIOS 1.27.0) -- DELL0501 absent in
    updated BIOS, intel_backlight works natively (no regression).

Signed-off-by: Chitransh Mandhaniya <Chitransh_Mandhaniya@dell.com>
---
 drivers/acpi/video_detect.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
index e3b69f876d24..1af14e04e597 100644
--- a/drivers/acpi/video_detect.c
+++ b/drivers/acpi/video_detect.c
@@ -883,6 +883,14 @@ static const struct dmi_system_id video_detect_dmi_table[] = {
 		DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 7770 AIO"),
 		},
 	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Dell OptiPlex AIO 7410 35W */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex AIO 7410 35W"),
+		},
+	},
 
 	/*
 	 * Models which have nvidia-ec-wmi support, but should not use it.
-- 
2.43.0