platform/x86: dell-uart-backlight: Use acpi_video_get_backlight_type()

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: 484bae9e4d6a ("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>

diff --git a/drivers/platform/x86/dell/Kconfig b/drivers/platform/x86/dell/Kconfig
index 85a78ef..309236c 100644 (file)
--- a/drivers/platform/x86/dell/Kconfig
+++ b/drivers/platform/x86/dell/Kconfig
@@ -161,6 +161,7 @@ config DELL_SMO8800
 config DELL_UART_BACKLIGHT
        tristate "Dell AIO UART Backlight driver"
        depends on ACPI
+       depends on ACPI_VIDEO
        depends on BACKLIGHT_CLASS_DEVICE
        depends on SERIAL_DEV_BUS
        help

diff --git a/drivers/platform/x86/dell/dell-uart-backlight.c b/drivers/platform/x86/dell/dell-uart-backlight.c
index 87d2a20..3995f90 100644 (file)
--- a/drivers/platform/x86/dell/dell-uart-backlight.c
+++ b/drivers/platform/x86/dell/dell-uart-backlight.c
@@ -20,6 +20,7 @@
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/wait.h>
+#include <acpi/video.h>
 #include "../serdev_helpers.h"
 
 /* The backlight controller must respond within 1 second */
@@ -332,10 +333,17 @@ struct serdev_device_driver dell_uart_bl_serdev_driver = {
 
 static int dell_uart_bl_pdev_probe(struct platform_device *pdev)
 {
+       enum acpi_backlight_type bl_type;
        struct serdev_device *serdev;
        struct device *ctrl_dev;
        int ret;
 
+       bl_type = acpi_video_get_backlight_type();
+       if (bl_type != acpi_backlight_dell_uart) {
+               dev_dbg(&pdev->dev, "Not loading (ACPI backlight type = %d)\n", bl_type);
+               return -ENODEV;
+       }
+
        ctrl_dev = get_serdev_controller("DELL0501", NULL, 0, "serial0");
        if (IS_ERR(ctrl_dev))
                return PTR_ERR(ctrl_dev);