linux-stable/drivers/gpu/drm/i915/display/intel_acpi.h
Hans de Goede 3c8b6a399e drm/i915: Call acpi_video_register_backlight() (v3)
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

Changes in v3:
-Add a new intel_acpi_video_register() helper which checks if a panel
 is present and then calls acpi_video_register_backlight()

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
2022-09-03 12:16:53 +02:00

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C

/* SPDX-License-Identifier: MIT */
/*
* Copyright © 2019 Intel Corporation
*/
#ifndef __INTEL_ACPI_H__
#define __INTEL_ACPI_H__
struct drm_i915_private;
#ifdef CONFIG_ACPI
void intel_register_dsm_handler(void);
void intel_unregister_dsm_handler(void);
void intel_dsm_get_bios_data_funcs_supported(struct drm_i915_private *i915);
void intel_acpi_device_id_update(struct drm_i915_private *i915);
void intel_acpi_assign_connector_fwnodes(struct drm_i915_private *i915);
void intel_acpi_video_register(struct drm_i915_private *i915);
#else
static inline void intel_register_dsm_handler(void) { return; }
static inline void intel_unregister_dsm_handler(void) { return; }
static inline
void intel_dsm_get_bios_data_funcs_supported(struct drm_i915_private *i915) { return; }
static inline
void intel_acpi_device_id_update(struct drm_i915_private *i915) { return; }
static inline
void intel_acpi_assign_connector_fwnodes(struct drm_i915_private *i915) { return; }
static inline
void intel_acpi_video_register(struct drm_i915_private *i915) { return; }
#endif /* CONFIG_ACPI */
#endif /* __INTEL_ACPI_H__ */