platform/x86: apple-gmux: Add acpi_video_get_backlight_type() check

Make apple-gmux backlight registration honor the acpi_backlight=...
kernel commandline option which is used to select the backlight
control method on x86/ACPI devices.

Reported-and-tested-by: Aditya Garg <gargaditya08@live.com>
Link: https://lore.kernel.org/platform-driver-x86/BM1PR01MB0931B467250831916F7C55B3B8A59@BM1PR01MB0931.INDPRD01.PROD.OUTLOOK.COM/
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230307113813.359743-1-hdegoede@redhat.com

diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
index 757fd71c900f12b49f48eee59035198ee713ab3f..ad81cb1df8f24ee8855aa5f81741f6cbabe5ef89 100644 (file)
--- a/drivers/platform/x86/apple-gmux.c
+++ b/drivers/platform/x86/apple-gmux.c
@@ -23,6 +23,7 @@
 #include <linux/pci.h>
 #include <linux/vga_switcheroo.h>
 #include <linux/debugfs.h>
+#include <acpi/video.h>
 #include <asm/io.h>
 
 /**
@@ -781,8 +782,9 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
        struct apple_gmux_data *gmux_data;
        struct resource *res;
        struct backlight_properties props;
-       struct backlight_device *bdev;
+       struct backlight_device *bdev = NULL;
        u8 ver_major, ver_minor, ver_release;
+       bool register_bdev = true;
        int ret = -ENXIO;
        acpi_status status;
        unsigned long long gpe;
@@ -859,33 +861,38 @@ get_version:
        props.type = BACKLIGHT_PLATFORM;
        props.max_brightness = gmux_read32(gmux_data, GMUX_PORT_MAX_BRIGHTNESS);
 
-       /*
-        * Currently it's assumed that the maximum brightness is less than
-        * 2^24 for compatibility with old gmux versions. Cap the max
-        * brightness at this value, but print a warning if the hardware
-        * reports something higher so that it can be fixed.
-        */
-       if (WARN_ON(props.max_brightness > GMUX_MAX_BRIGHTNESS))
-               props.max_brightness = GMUX_MAX_BRIGHTNESS;
-
-       bdev = backlight_device_register("gmux_backlight", &pnp->dev,
-                                        gmux_data, &gmux_bl_ops, &props);
-       if (IS_ERR(bdev)) {
-               ret = PTR_ERR(bdev);
-               goto err_unmap;
-       }
-
-       gmux_data->bdev = bdev;
-       bdev->props.brightness = gmux_get_brightness(bdev);
-       backlight_update_status(bdev);
+#if IS_REACHABLE(CONFIG_ACPI_VIDEO)
+       register_bdev = acpi_video_get_backlight_type() == acpi_backlight_apple_gmux;
+#endif
+       if (register_bdev) {
+               /*
+                * Currently it's assumed that the maximum brightness is less than
+                * 2^24 for compatibility with old gmux versions. Cap the max
+                * brightness at this value, but print a warning if the hardware
+                * reports something higher so that it can be fixed.
+                */
+               if (WARN_ON(props.max_brightness > GMUX_MAX_BRIGHTNESS))
+                       props.max_brightness = GMUX_MAX_BRIGHTNESS;
+
+               bdev = backlight_device_register("gmux_backlight", &pnp->dev,
+                                                gmux_data, &gmux_bl_ops, &props);
+               if (IS_ERR(bdev)) {
+                       ret = PTR_ERR(bdev);
+                       goto err_unmap;
+               }
 
-       /*
-        * The backlight situation on Macs is complicated. If the gmux is
-        * present it's the best choice, because it always works for
-        * backlight control and supports more levels than other options.
-        * Disable the other backlight choices.
-        */
-       apple_bl_unregister();
+               gmux_data->bdev = bdev;
+               bdev->props.brightness = gmux_get_brightness(bdev);
+               backlight_update_status(bdev);
+
+               /*
+                * The backlight situation on Macs is complicated. If the gmux is
+                * present it's the best choice, because it always works for
+                * backlight control and supports more levels than other options.
+                * Disable the other backlight choices.
+                */
+               apple_bl_unregister();
+       }
 
        gmux_data->power_state = VGA_SWITCHEROO_ON;