The dell-uart-backlight driver supports backlight control on Dell All In
One (AIO) models using a backlight controller board connected to an UART.
In DSDT this uart port will be defined as:
Name (_HID, "DELL0501")
Name (_CID, EisaId ("PNP0501")
Now the first AIO has turned up which has not only the DSDT bits for this,
but also an actual controller attached to the UART, yet it is not using
this controller for backlight control.
Use the acpi_video_get_backlight_type() function from the ACPI video-detect
code to check if the dell-uart-backlight driver should actually be used.
This allows reusing the existing ACPI video-detect infra to override
the backlight control method on the commandline or with DMI quirks.
Fixes: 484bae9e4d ("platform/x86: Add new Dell UART backlight driver")
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://patch.msgid.link/20240814190159.15650-3-hdegoede@redhat.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Dell All In One (AIO) models released after 2017 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")
Instead of having a separate ACPI device with an UartSerialBusV2() resource
to model the backlight-controller, which would be the standard way to do
this.
The acpi_quirk_skip_serdev_enumeration() has special handling for this
and it will make the serial port code create a serdev controller device
for the UART instead of a /dev/ttyS0 char-dev. It will also create
a dell-uart-backlight driver platform device for this driver to bind too.
This new kernel module contains 2 drivers for this:
1. A simple platform driver which creates the actual serdev device
(with the serdev controller device as parent)
2. A serdev driver for the created serdev device which exports
the backlight functionality uses a standard backlight class device.
Reported-by: Roman Bogoyev <roman@computercheck.com.au>
Tested-by: Roman Bogoyev <roman@computercheck.com.au>
Tested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Co-developed-by: AceLan Kao <acelan.kao@canonical.com>
Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20240513144603.93874-2-hdegoede@redhat.com
