On machins without an i915 opregion the acpi_video driver immediately probes the ACPI video bus and used to also immediately register acpi_video# backlight devices when supported.
Once the drm/kms driver then loaded later and possibly registered a native backlight device then the drivers/acpi/video_detect.c code unregistered the acpi_video0 device to avoid there being 2 backlight devices (when acpi_video_get_backlight_type()==native). This means that userspace used to briefly see 2 devices and the disappearing of acpi_video0 after a brief time confuses the systemd backlight level save/restore code, see e.g.: https://bbs.archlinux.org/viewtopic.php?id=269920 To fix this the ACPI video code has been modified to make backlight class device registration a separate step, relying on the drm/kms driver to ask for the acpi_video backlight registration after it is done setting up its native backlight device. Add a call to the new acpi_video_register_backlight() after the i915 calls acpi_video_register() (after setting up the i915 opregion) so that the acpi_video backlight devices get registered on systems where the i915 native backlight device is not registered. Changes in v2: -Only call acpi_video_register_backlight() when a panel is detected Signed-off-by: Hans de Goede <hdego...@redhat.com> --- drivers/gpu/drm/i915/display/intel_display.c | 8 ++++++++ drivers/gpu/drm/i915/display/intel_panel.c | 3 +++ drivers/gpu/drm/i915/i915_drv.h | 2 ++ 3 files changed, 13 insertions(+) diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c index 533fff79aeda..e7a4584e3189 100644 --- a/drivers/gpu/drm/i915/display/intel_display.c +++ b/drivers/gpu/drm/i915/display/intel_display.c @@ -9082,6 +9082,14 @@ void intel_display_driver_register(struct drm_i915_private *i915) /* Must be done after probing outputs */ intel_opregion_register(i915); acpi_video_register(); + /* + * Only call this if i915 is driving the internal panel. If the internal + * panel is not driven by i915 then another GPU driver may still register + * a native backlight driver later and this should only be called after + * any native backlights have been registered. + */ + if (i915->have_panel) + acpi_video_register_backlight(); intel_audio_init(i915); diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c index 237a40623dd7..4536c527f50c 100644 --- a/drivers/gpu/drm/i915/display/intel_panel.c +++ b/drivers/gpu/drm/i915/display/intel_panel.c @@ -646,8 +646,11 @@ intel_panel_mode_valid(struct intel_connector *connector, int intel_panel_init(struct intel_connector *connector) { + struct drm_i915_private *dev_priv = to_i915(connector->base.dev); struct intel_panel *panel = &connector->panel; + dev_priv->have_panel = true; + intel_backlight_init_funcs(panel); drm_dbg_kms(connector->base.dev, diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 086bbe8945d6..a632d9b87bc8 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -756,6 +756,8 @@ struct drm_i915_private { bool ipc_enabled; + bool have_panel; + struct intel_audio_private audio; struct i915_pmu pmu; -- 2.37.2
