Systemd/src/login/logind-brightness.h

/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once

#include "sd-bus.h"
#include "sd-device.h"

#include "logind.h"

int manager_write_brightness(Manager *m, sd_device *device, uint32_t brightness, sd_bus_message *message);
license: LGPL-2.1+ -> LGPL-2.1-or-later 2020-11-09 05:23:58 +01:00			`/* SPDX-License-Identifier: LGPL-2.1-or-later */`
logind: add SetBrightness() bus call for setting brightness of leds/backlight devices associated with a seat This augments the drm/input device management by adding a single method call for setting the brightness of an "leds" or "backlight" kernel class device. This method call requires no privileges to call, but a caller can only change the brightness on sessions that are currently active, and they must own the session. This does not do enumeration of such class devices, feature or range probing, chnage notification; it doesn't help associating graphics or input devices with their backlight or leds devices. For all that clients should go directly to udev/sysfs. The SetBrightness() call is just for executing the actual change operation, that is otherwise privileged. Example line: busctl call org.freedesktop.login1 /org/freedesktop/login1/session/self org.freedesktop.login1.Session SetBrightness ssu "backlight" "intel_backlight" 200 The parameter the SetBrightness() call takes are the kernel subsystem (i.e. "leds" or "backlight"), the device name, and the brightness value. On some hw setting the brightness is slow, and implementation and write access to the sysfs knobs exposes this slowness. Due to this we'll fork off a writer process in the background so that logind doesn't have to block. Moreover, write requestes are coalesced: when a write request is enqueued while one is already being executed it is queued. When another write reques is then enqueued the earlier one is replaced by the newer one, so that only one queued write request per device remains at any time. Method replies are sent as soon as the first write request that happens after the request was received is completed. It is recommended that bus clients turn off the "expect_reply" flag on the dbus messages they send though, that relieves logind from sending completion notification and is particularly a good idea if clients implement reactive UI sliders that send a quick secession of write requests. Replaces: #12413 2019-04-28 11:07:56 +02:00			`#pragma once`

			`#include "sd-bus.h"`
			`#include "sd-device.h"`

			`#include "logind.h"`

			`int manager_write_brightness(Manager m, sd_device device, uint32_t brightness, sd_bus_message *message);`