This adds a function that creates a backlight device for a connector. It does not deal with the KMS backlight ABI proposition[1] to add a connector property. It only takes the current best practise to standardise the creation of a backlight device for DRM drivers while we wait for the property.
The brightness value is set using a connector state variable and an atomic commit. I have looked through some of the backlight users and this is what I've found: GNOME [2] --------- Brightness range: 0-100 Scale: Assumes perceptual Avoids setting the sysfs brightness value to zero if max_brightness >= 99. Can connect connector and backlight using the sysfs device. KDE [3] ------- Brightness range: 0-100 Scale: Assumes perceptual Weston [4] ---------- Brightness range: 0-255 Scale: Assumes perceptual Chromium OS [5] --------------- Brightness range: 0-100 Scale: Depends on the sysfs file 'scale' which is a recent addition (2019) xserver [6] ----------- Brightness range: 0-x (driver specific) (1 is minimum, 0 is OFF) Scale: Assumes perceptual The builtin modesetting driver[7] does not support Backlight, Intel[8] does. [1] https://lore.kernel.org/dri-devel/4b17ba08-39f3-57dd-5aad-d37d844b0...@linux.intel.com/ [2] https://gitlab.gnome.org/GNOME/gnome-settings-daemon/-/blob/master/plugins/power/gsd-backlight.c [3] https://github.com/KDE/powerdevil/blob/master/daemon/backends/upower/backlighthelper.cpp [4] https://gitlab.freedesktop.org/wayland/weston/-/blob/master/libweston/backend-drm/drm.c [5] https://chromium.googlesource.com/chromiumos/platform2/+/refs/heads/master/power_manager/powerd/system/internal_backlight.cc [6] https://github.com/freedesktop/xorg-randrproto/blob/master/randrproto.txt [7] https://gitlab.freedesktop.org/xorg/xserver/-/blob/master/hw/xfree86/drivers/modesetting/drmmode_display.c [8] https://gitlab.freedesktop.org/xorg/driver/xf86-video-intel/-/blob/master/src/backlight.c Cc: Hans de Goede <hdego...@redhat.com> Cc: Jani Nikula <jani.nik...@linux.intel.com> Cc: Martin Peres <martin.pe...@linux.intel.com> Cc: Daniel Thompson <daniel.thomp...@linaro.org> Signed-off-by: Noralf Trønnes <nor...@tronnes.org> --- Documentation/gpu/drm-kms-helpers.rst | 6 + drivers/gpu/drm/Kconfig | 7 ++ drivers/gpu/drm/Makefile | 1 + drivers/gpu/drm/drm_backlight_helper.c | 154 +++++++++++++++++++++++++ include/drm/drm_backlight_helper.h | 9 ++ include/drm/drm_connector.h | 10 ++ 6 files changed, 187 insertions(+) create mode 100644 drivers/gpu/drm/drm_backlight_helper.c create mode 100644 include/drm/drm_backlight_helper.h diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst index 9668a7fe2408..29a2f4b49fd2 100644 --- a/Documentation/gpu/drm-kms-helpers.rst +++ b/Documentation/gpu/drm-kms-helpers.rst @@ -411,3 +411,9 @@ SHMEM GEM Helper Reference .. kernel-doc:: drivers/gpu/drm/drm_gem_shmem_helper.c :export: + +Backlight Helper Reference +========================== + +.. kernel-doc:: drivers/gpu/drm/drm_backlight_helper.c + :export: diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig index d0aa6cff2e02..f6e13e18c9ca 100644 --- a/drivers/gpu/drm/Kconfig +++ b/drivers/gpu/drm/Kconfig @@ -224,6 +224,13 @@ config DRM_GEM_SHMEM_HELPER help Choose this if you need the GEM shmem helper functions +config DRM_BACKLIGHT_HELPER + bool + depends on DRM + select BACKLIGHT_CLASS_DEVICE + help + Choose this if you need the backlight device helper functions + config DRM_VM bool depends on DRM && MMU diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile index 6493088a0fdd..0d17662dde0a 100644 --- a/drivers/gpu/drm/Makefile +++ b/drivers/gpu/drm/Makefile @@ -52,6 +52,7 @@ drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o drm_kms_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o drm_kms_helper-$(CONFIG_DRM_DP_CEC) += drm_dp_cec.o +drm_kms_helper-$(CONFIG_DRM_BACKLIGHT_HELPER) += drm_backlight_helper.o obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o obj-$(CONFIG_DRM_DEBUG_SELFTEST) += selftests/ diff --git a/drivers/gpu/drm/drm_backlight_helper.c b/drivers/gpu/drm/drm_backlight_helper.c new file mode 100644 index 000000000000..06e6a75d1d0a --- /dev/null +++ b/drivers/gpu/drm/drm_backlight_helper.c @@ -0,0 +1,154 @@ +// SPDX-License-Identifier: GPL-2.0 OR MIT +/* + * Copyright 2020 Noralf Trønnes + */ + +#include <linux/backlight.h> + +#include <drm/drm_atomic.h> +#include <drm/drm_connector.h> +#include <drm/drm_drv.h> +#include <drm/drm_file.h> + +static int drm_backlight_update_status(struct backlight_device *bd) +{ + struct drm_connector *connector = bl_get_data(bd); + struct drm_connector_state *connector_state; + struct drm_device *dev = connector->dev; + struct drm_modeset_acquire_ctx ctx; + struct drm_atomic_state *state; + int ret; + + state = drm_atomic_state_alloc(dev); + if (!state) + return -ENOMEM; + + drm_modeset_acquire_init(&ctx, 0); + state->acquire_ctx = &ctx; +retry: + connector_state = drm_atomic_get_connector_state(state, connector); + if (IS_ERR(connector_state)) { + ret = PTR_ERR(connector_state); + goto out; + } + + connector_state->backlight_brightness = bd->props.brightness; + + ret = drm_atomic_commit(state); +out: + if (ret == -EDEADLK) { + drm_atomic_state_clear(state); + drm_modeset_backoff(&ctx); + goto retry; + } + + drm_atomic_state_put(state); + + drm_modeset_drop_locks(&ctx); + drm_modeset_acquire_fini(&ctx); + + return ret; +} + +static int drm_backlight_get_brightness(struct backlight_device *bd) +{ + struct drm_connector *connector = bl_get_data(bd); + struct drm_device *dev = connector->dev; + int brightness; + + drm_modeset_lock(&dev->mode_config.connection_mutex, NULL); + brightness = connector->state->backlight_brightness; + drm_modeset_unlock(&dev->mode_config.connection_mutex); + + return brightness; +} + +static const struct backlight_ops drm_backlight_ops = { + .get_brightness = drm_backlight_get_brightness, + .update_status = drm_backlight_update_status, +}; + +/* Can be exported for drivers carrying a legacy name */ +static int drm_backlight_register_with_name(struct drm_connector *connector, const char *name) +{ + struct backlight_device *bd; + const struct backlight_properties props = { + .type = BACKLIGHT_RAW, + .scale = BACKLIGHT_SCALE_NON_LINEAR, + .max_brightness = 100, + }; + + if (WARN_ON(!drm_core_check_feature(connector->dev, DRIVER_MODESET) || + !drm_drv_uses_atomic_modeset(connector->dev) || + !connector->kdev)) + return -EINVAL; + + bd = backlight_device_register(name, connector->kdev, connector, + &drm_backlight_ops, &props); + if (IS_ERR(bd)) + return PTR_ERR(bd); + + connector->backlight = bd; + + return 0; +} + +/** + * drm_backlight_register() - Register a backlight device for a connector + * @connector: Connector + * + * This function registers a backlight device for @connector with the following + * characteristics: + * + * - The connector sysfs device is used as a parent device for the backlight device. + * Userspace can use this to connect backlight device and connector. + * - Name will be on the form: **card0-HDMI-A-1-backlight** + * - Type is "raw" + * - Scale is "non-linear" (perceptual) + * - Max brightness is 100 giving a range of 0-100 inclusive + * - Reading sysfs **brightness** returns the backlight device property + * - Reading sysfs **actual_brightness** returns the connector state value + * - Writing sysfs **bl_power** is ignored, the DPMS connector property should + * be used to control power. + * - Backlight device suspend/resume events are ignored. + * + * Note: + * + * Brightness zero should not turn off backlight it should be the minimum + * brightness, DPMS handles power. + * + * This function must be called from &drm_connector_funcs->late_register() since + * it depends on the sysfs device. + * + * Returns: + * Zero on success or negative error code on failure. + */ +int drm_backlight_register(struct drm_connector *connector) +{ + const char *name = NULL; + int ret; + + name = kasprintf(GFP_KERNEL, "card%d-%s-backlight", + connector->dev->primary->index, connector->name); + if (!name) + return -ENOMEM; + + ret = drm_backlight_register_with_name(connector, name); + kfree(name); + + return ret; +} +EXPORT_SYMBOL(drm_backlight_register); + +/** + * drm_backlight_unregister() - Unregister backlight device + * @connector: Connector + * + * Unregister a backlight device. This must be called from the + * &drm_connector_funcs->early_unregister() callback. + */ +void drm_backlight_unregister(struct drm_connector *connector) +{ + backlight_device_unregister(connector->backlight); +} +EXPORT_SYMBOL(drm_backlight_unregister); diff --git a/include/drm/drm_backlight_helper.h b/include/drm/drm_backlight_helper.h new file mode 100644 index 000000000000..4151b66eb0b4 --- /dev/null +++ b/include/drm/drm_backlight_helper.h @@ -0,0 +1,9 @@ +/* SPDX-License-Identifier: GPL-2.0 OR MIT */ + +#ifndef _LINUX_DRM_BACKLIGHT_HELPER_H +#define _LINUX_DRM_BACKLIGHT_HELPER_H + +int drm_backlight_register(struct drm_connector *connector); +void drm_backlight_unregister(struct drm_connector *connector); + +#endif diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h index 221910948b37..ce678b694f45 100644 --- a/include/drm/drm_connector.h +++ b/include/drm/drm_connector.h @@ -32,6 +32,7 @@ #include <uapi/drm/drm_mode.h> +struct backlight_device; struct drm_connector_helper_funcs; struct drm_modeset_acquire_ctx; struct drm_device; @@ -656,6 +657,12 @@ struct drm_connector_state { */ u8 max_bpc; + /** + * @backlight_brightness: Brightness value of the connector backlight + * device. See drm_backlight_register(). + */ + u8 backlight_brightness; + /** * @hdr_output_metadata: * DRM blob property for HDR output metadata @@ -1422,6 +1429,9 @@ struct drm_connector { /** @hdr_sink_metadata: HDR Metadata Information read from sink */ struct hdr_sink_metadata hdr_sink_metadata; + + /** @backlight: Backlight device. See drm_backlight_register() */ + struct backlight_device *backlight; }; #define obj_to_connector(x) container_of(x, struct drm_connector, base) -- 2.23.0 _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
