On Thu, Dec 15, 2022 at 10:41 AM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > The apple-gmux driver only binds to old GMUX devices which have an > IORESOURCE_IO resource (using inb()/outb()) rather then memory-mapped > IO (IORESOURCE_MEM). > > T2 MacBooks use the new style GMUX devices (with IORESOURCE_MEM access), > so these are not supported by the apple-gmux driver. This is not a problem > since they have working ACPI video backlight support. > > But the apple_gmux_present() helper only checks if an ACPI device with > the "APP000B" HID is present, causing acpi_video_get_backlight_type() > to return acpi_backlight_apple_gmux disabling the acpi_video backlight > device. > > Add a new apple_gmux_backlight_present() helper which checks that > the "APP000B" device actually is an old GMUX device with an IORESOURCE_IO > resource. > > This fixes the acpi_video0 backlight no longer registering on T2 MacBooks. > > Note people are working to add support for the new style GMUX to Linux: > https://github.com/kekrby/linux-t2/commits/wip/hybrid-graphics > > Once this lands this patch should be reverted so that > acpi_video_get_backlight_type() also prefers the gmux on new style GMUX > MacBooks, but for now this is necessary to avoid regressing backlight > control on T2 Macs. > > Fixes: 21245df307cb ("ACPI: video: Add Apple GMUX brightness control detection") > Reported-and-tested-by: Aditya Garg <gargaditya08@xxxxxxxx> > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> > --- > drivers/acpi/video_detect.c | 23 ++++++++++++++++++++++- > 1 file changed, 22 insertions(+), 1 deletion(-) > > diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c > index a934bbc9dd37..1b78c7434492 100644 > --- a/drivers/acpi/video_detect.c > +++ b/drivers/acpi/video_detect.c > @@ -34,6 +34,7 @@ > #include <linux/module.h> > #include <linux/pci.h> > #include <linux/platform_data/x86/nvidia-wmi-ec-backlight.h> > +#include <linux/pnp.h> > #include <linux/types.h> > #include <linux/workqueue.h> > #include <acpi/video.h> > @@ -105,6 +106,26 @@ static bool nvidia_wmi_ec_supported(void) > } > #endif > > +static bool apple_gmux_backlight_present(void) > +{ > + struct acpi_device *adev; > + struct device *dev; > + > + adev = acpi_dev_get_first_match_dev(GMUX_ACPI_HID, NULL, -1); > + if (!adev) > + return false; > + > + dev = acpi_get_first_physical_node(adev); > + if (!dev) > + return false; > + > + /* > + * drivers/platform/x86/apple-gmux.c only supports old style > + * Apple GMUX with an IO-resource. > + */ > + return pnp_get_resource(to_pnp_dev(dev), IORESOURCE_IO, 0) != NULL; > +} > + > /* Force to use vendor driver when the ACPI device is known to be > * buggy */ > static int video_detect_force_vendor(const struct dmi_system_id *d) > @@ -767,7 +788,7 @@ static enum acpi_backlight_type __acpi_video_get_backlight_type(bool native) > if (nvidia_wmi_ec_present) > return acpi_backlight_nvidia_wmi_ec; > > - if (apple_gmux_present()) > + if (apple_gmux_backlight_present()) > return acpi_backlight_apple_gmux; > > /* Use ACPI video if available, except when native should be preferred. */ > -- Applied as 6.2-rc material, thanks!
