[thirdparty/systemd.git] / src / backlight / backlight.c

/* SPDX-License-Identifier: LGPL-2.1+ */
/***
  Copyright 2013 Lennart Poettering
***/

#include "libudev.h"

#include "alloc-util.h"
#include "def.h"
#include "escape.h"
#include "fileio.h"
#include "mkdir.h"
#include "parse-util.h"
#include "proc-cmdline.h"
#include "string-util.h"
#include "udev-util.h"
#include "util.h"

static struct udev_device *find_pci_or_platform_parent(struct udev_device *device) {
        struct udev_device *parent;
        const char *subsystem, *sysname;

        assert(device);

        parent = udev_device_get_parent(device);
        if (!parent)
                return NULL;

        subsystem = udev_device_get_subsystem(parent);
        if (!subsystem)
                return NULL;

        sysname = udev_device_get_sysname(parent);
        if (!sysname)
                return NULL;

        if (streq(subsystem, "drm")) {
                const char *c;

                c = startswith(sysname, "card");
                if (!c)
                        return NULL;

                c += strspn(c, DIGITS);
                if (*c == '-') {
                        /* A connector DRM device, let's ignore all but LVDS and eDP! */

                        if (!startswith(c, "-LVDS-") &&
                            !startswith(c, "-Embedded DisplayPort-"))
                                return NULL;
                }

        } else if (streq(subsystem, "pci")) {
                const char *value;

                value = udev_device_get_sysattr_value(parent, "class");
                if (value) {
                        unsigned long class = 0;

                        if (safe_atolu(value, &class) < 0) {
                                log_warning("Cannot parse PCI class %s of device %s:%s.",
                                            value, subsystem, sysname);
                                return NULL;
                        }

                        /* Graphics card */
                        if (class == 0x30000)
                                return parent;
                }

        } else if (streq(subsystem, "platform"))
                return parent;

        return find_pci_or_platform_parent(parent);
}

static bool same_device(struct udev_device *a, struct udev_device *b) {
        assert(a);
        assert(b);

        if (!streq_ptr(udev_device_get_subsystem(a), udev_device_get_subsystem(b)))
                return false;

        if (!streq_ptr(udev_device_get_sysname(a), udev_device_get_sysname(b)))
                return false;

        return true;
}

static bool validate_device(struct udev *udev, struct udev_device *device) {
        _cleanup_(udev_enumerate_unrefp) struct udev_enumerate *enumerate = NULL;
        struct udev_list_entry *item = NULL, *first = NULL;
        struct udev_device *parent;
        const char *v, *subsystem;
        int r;

        assert(udev);
        assert(device);

        /* Verify whether we should actually care for a specific
         * backlight device. For backlight devices there might be
         * multiple ways to access the same control: "firmware"
         * (i.e. ACPI), "platform" (i.e. via the machine's EC) and
         * "raw" (via the graphics card). In general we should prefer
         * "firmware" (i.e. ACPI) or "platform" access over "raw"
         * access, in order not to confuse the BIOS/EC, and
         * compatibility with possible low-level hotkey handling of
         * screen brightness. The kernel will already make sure to
         * expose only one of "firmware" and "platform" for the same
         * device to userspace. However, we still need to make sure
         * that we use "raw" only if no "firmware" or "platform"
         * device for the same device exists. */

        subsystem = udev_device_get_subsystem(device);
        if (!streq_ptr(subsystem, "backlight"))
                return true;

        v = udev_device_get_sysattr_value(device, "type");
        if (!streq_ptr(v, "raw"))
                return true;

        parent = find_pci_or_platform_parent(device);
        if (!parent)
                return true;

        subsystem = udev_device_get_subsystem(parent);
        if (!subsystem)
                return true;

        enumerate = udev_enumerate_new(udev);
        if (!enumerate)
                return true;

        r = udev_enumerate_add_match_subsystem(enumerate, "backlight");
        if (r < 0)
                return true;

        r = udev_enumerate_scan_devices(enumerate);
        if (r < 0)
                return true;

        first = udev_enumerate_get_list_entry(enumerate);
        udev_list_entry_foreach(item, first) {
                _cleanup_(udev_device_unrefp) struct udev_device *other;
                struct udev_device *other_parent;
                const char *other_subsystem;

                other = udev_device_new_from_syspath(udev, udev_list_entry_get_name(item));
                if (!other)
                        return true;

                if (same_device(device, other))
                        continue;

                v = udev_device_get_sysattr_value(other, "type");
                if (!STRPTR_IN_SET(v, "platform", "firmware"))
                        continue;

                /* OK, so there's another backlight device, and it's a
                 * platform or firmware device, so, let's see if we
                 * can verify it belongs to the same device as
                 * ours. */
                other_parent = find_pci_or_platform_parent(other);
                if (!other_parent)
                        continue;

                if (same_device(parent, other_parent)) {
                        /* Both have the same PCI parent, that means
                         * we are out. */
                        log_debug("Skipping backlight device %s, since device %s is on same PCI device and takes precedence.",
                                  udev_device_get_sysname(device),
                                  udev_device_get_sysname(other));
                        return false;
                }

                other_subsystem = udev_device_get_subsystem(other_parent);
                if (streq_ptr(other_subsystem, "platform") && streq_ptr(subsystem, "pci")) {
                        /* The other is connected to the platform bus
                         * and we are a PCI device, that also means we
                         * are out. */
                        log_debug("Skipping backlight device %s, since device %s is a platform device and takes precedence.",
                                  udev_device_get_sysname(device),
                                  udev_device_get_sysname(other));
                        return false;
                }
        }

        return true;
}

static unsigned get_max_brightness(struct udev_device *device) {
        int r;
        const char *max_brightness_str;
        unsigned max_brightness;

        max_brightness_str = udev_device_get_sysattr_value(device, "max_brightness");
        if (!max_brightness_str) {
                log_warning("Failed to read 'max_brightness' attribute.");
                return 0;
        }

        r = safe_atou(max_brightness_str, &max_brightness);
        if (r < 0) {
                log_warning_errno(r, "Failed to parse 'max_brightness' \"%s\": %m", max_brightness_str);
                return 0;
        }

        if (max_brightness <= 0) {
                log_warning("Maximum brightness is 0, ignoring device.");
                return 0;
        }

        return max_brightness;
}

/* Some systems turn the backlight all the way off at the lowest levels.
 * clamp_brightness clamps the saved brightness to at least 1 or 5% of
 * max_brightness in case of 'backlight' subsystem. This avoids preserving
 * an unreadably dim screen, which would otherwise force the user to
 * disable state restoration. */
static void clamp_brightness(struct udev_device *device, char **value, unsigned max_brightness) {
        unsigned brightness, new_brightness, min_brightness;
        const char *subsystem;
        int r;

        r = safe_atou(*value, &brightness);
        if (r < 0) {
                log_warning_errno(r, "Failed to parse brightness \"%s\": %m", *value);
                return;
        }

        subsystem = udev_device_get_subsystem(device);
        if (streq_ptr(subsystem, "backlight"))
                min_brightness = MAX(1U, max_brightness/20);
        else
                min_brightness = 0;

        new_brightness = CLAMP(brightness, min_brightness, max_brightness);
        if (new_brightness != brightness) {
                char *old_value = *value;

                r = asprintf(value, "%u", new_brightness);
                if (r < 0) {
                        log_oom();
                        return;
                }

                log_info("Saved brightness %s %s to %s.", old_value,
                         new_brightness > brightness ?
                         "too low; increasing" : "too high; decreasing",
                         *value);

                free(old_value);
        }
}

static bool shall_clamp(struct udev_device *d) {
        const char *s;
        int r;

        assert(d);

        s = udev_device_get_property_value(d, "ID_BACKLIGHT_CLAMP");
        if (!s)
                return true;

        r = parse_boolean(s);
        if (r < 0) {
                log_debug_errno(r, "Failed to parse ID_BACKLIGHT_CLAMP property, ignoring: %m");
                return true;
        }

        return r;
}

int main(int argc, char *argv[]) {
        _cleanup_(udev_unrefp) struct udev *udev = NULL;
        _cleanup_(udev_device_unrefp) struct udev_device *device = NULL;
        _cleanup_free_ char *escaped_ss = NULL, *escaped_sysname = NULL, *escaped_path_id = NULL;
        const char *sysname, *path_id, *ss, *saved;
        unsigned max_brightness;
        int r;

        if (argc != 3) {
                log_error("This program requires two arguments.");
                return EXIT_FAILURE;
        }

        log_set_target(LOG_TARGET_AUTO);
        log_parse_environment();
        log_open();

        umask(0022);

        r = mkdir_p("/var/lib/systemd/backlight", 0755);
        if (r < 0) {
                log_error_errno(r, "Failed to create backlight directory /var/lib/systemd/backlight: %m");
                return EXIT_FAILURE;
        }

        udev = udev_new();
        if (!udev) {
                log_oom();
                return EXIT_FAILURE;
        }

        sysname = strchr(argv[2], ':');
        if (!sysname) {
                log_error("Requires a subsystem and sysname pair specifying a backlight device.");
                return EXIT_FAILURE;
        }

        ss = strndupa(argv[2], sysname - argv[2]);

        sysname++;

        if (!STR_IN_SET(ss, "backlight", "leds")) {
                log_error("Not a backlight or LED device: '%s:%s'", ss, sysname);
                return EXIT_FAILURE;
        }

        errno = 0;
        device = udev_device_new_from_subsystem_sysname(udev, ss, sysname);
        if (!device) {
                if (errno > 0)
                        log_error_errno(errno, "Failed to get backlight or LED device '%s:%s': %m", ss, sysname);
                else
                        log_oom();

                return EXIT_FAILURE;
        }

        /* If max_brightness is 0, then there is no actual backlight
         * device. This happens on desktops with Asus mainboards
         * that load the eeepc-wmi module.
         */
        max_brightness = get_max_brightness(device);
        if (max_brightness == 0)
                return EXIT_SUCCESS;

        escaped_ss = cescape(ss);
        if (!escaped_ss) {
                log_oom();
                return EXIT_FAILURE;
        }

        escaped_sysname = cescape(sysname);
        if (!escaped_sysname) {
                log_oom();
                return EXIT_FAILURE;
        }

        path_id = udev_device_get_property_value(device, "ID_PATH");
        if (path_id) {
                escaped_path_id = cescape(path_id);
                if (!escaped_path_id) {
                        log_oom();
                        return EXIT_FAILURE;
                }

                saved = strjoina("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_ss, ":", escaped_sysname);
        } else
                saved = strjoina("/var/lib/systemd/backlight/", escaped_ss, ":", escaped_sysname);

        /* If there are multiple conflicting backlight devices, then
         * their probing at boot-time might happen in any order. This
         * means the validity checking of the device then is not
         * reliable, since it might not see other devices conflicting
         * with a specific backlight. To deal with this, we will
         * actively delete backlight state files at shutdown (where
         * device probing should be complete), so that the validity
         * check at boot time doesn't have to be reliable. */

        if (streq(argv[1], "load")) {
                _cleanup_free_ char *value = NULL;
                bool clamp;

                if (shall_restore_state() == 0)
                        return EXIT_SUCCESS;

                if (!validate_device(udev, device))
                        return EXIT_SUCCESS;

                clamp = shall_clamp(device);

                r = read_one_line_file(saved, &value);
                if (r == -ENOENT) {
                        const char *curval;

                        /* Fallback to clamping current brightness or exit early if
                         * clamping is not supported/enabled. */
                        if (!clamp)
                                return EXIT_SUCCESS;

                        curval = udev_device_get_sysattr_value(device, "brightness");
                        if (!curval) {
                                log_warning("Failed to read 'brightness' attribute.");
                                return EXIT_FAILURE;
                        }

                        value = strdup(curval);
                        if (!value) {
                                log_oom();
                                return EXIT_FAILURE;
                        }
                } else if (r < 0) {
                        log_error_errno(r, "Failed to read %s: %m", saved);
                        return EXIT_FAILURE;
                }

                if (clamp)
                        clamp_brightness(device, &value, max_brightness);

                r = udev_device_set_sysattr_value(device, "brightness", value);
                if (r < 0) {
                        log_error_errno(r, "Failed to write system 'brightness' attribute: %m");
                        return EXIT_FAILURE;
                }

        } else if (streq(argv[1], "save")) {
                const char *value;

                if (!validate_device(udev, device)) {
                        unlink(saved);
                        return EXIT_SUCCESS;
                }

                value = udev_device_get_sysattr_value(device, "brightness");
                if (!value) {
                        log_error("Failed to read system 'brightness' attribute");
                        return EXIT_FAILURE;
                }

                r = write_string_file(saved, value, WRITE_STRING_FILE_CREATE);
                if (r < 0) {
                        log_error_errno(r, "Failed to write %s: %m", saved);
                        return EXIT_FAILURE;
                }

        } else {
                log_error("Unknown verb %s.", argv[1]);
                return EXIT_FAILURE;
        }

        return EXIT_SUCCESS;
}
Commit	Line	Data
53e1b683	1	/* SPDX-License-Identifier: LGPL-2.1+ */
3731acf1	2	/***
3731acf1	3	Copyright 2013 Lennart Poettering
3731acf1 LP	4	***/
3731acf1 LP	5
b4bbcaa9 TA	6	#include "libudev.h"
b4bbcaa9 TA	7
b5efdb8a	8	#include "alloc-util.h"
4f5dd394 LP	9	#include "def.h"
4f5dd394 LP	10	#include "escape.h"
3731acf1	11	#include "fileio.h"
4f5dd394	12	#include "mkdir.h"
4e731273 LP	13	#include "parse-util.h"
4e731273 LP	14	#include "proc-cmdline.h"
07630cea	15	#include "string-util.h"
1ca208fb	16	#include "udev-util.h"
4f5dd394	17	#include "util.h"
3731acf1	18
0f4ba83c LP	19	static struct udev_device find_pci_or_platform_parent(struct udev_device device) {
	20	struct udev_device *parent;
	21	const char subsystem, sysname;
	22
	23	assert(device);
	24
	25	parent = udev_device_get_parent(device);
	26	if (!parent)
	27	return NULL;
	28
	29	subsystem = udev_device_get_subsystem(parent);
	30	if (!subsystem)
	31	return NULL;
	32
	33	sysname = udev_device_get_sysname(parent);
	34	if (!sysname)
	35	return NULL;
	36
	37	if (streq(subsystem, "drm")) {
	38	const char *c;
	39
	40	c = startswith(sysname, "card");
	41	if (!c)
	42	return NULL;
	43
938d2699	44	c += strspn(c, DIGITS);
0f4ba83c LP	45	if (*c == '-') {
	46	/* A connector DRM device, let's ignore all but LVDS and eDP! */
	47
	48	if (!startswith(c, "-LVDS-") &&
	49	!startswith(c, "-Embedded DisplayPort-"))
	50	return NULL;
	51	}
	52
	53	} else if (streq(subsystem, "pci")) {
	54	const char *value;
	55
	56	value = udev_device_get_sysattr_value(parent, "class");
	57	if (value) {
39883f62	58	unsigned long class = 0;
0f4ba83c LP	59
0f4ba83c LP	60	if (safe_atolu(value, &class) < 0) {
938d2699 ZJS	61	log_warning("Cannot parse PCI class %s of device %s:%s.",
938d2699 ZJS	62	value, subsystem, sysname);
0f4ba83c LP	63	return NULL;
	64	}
	65
	66	/* Graphics card */
	67	if (class == 0x30000)
	68	return parent;
	69	}
	70
	71	} else if (streq(subsystem, "platform"))
	72	return parent;
	73
	74	return find_pci_or_platform_parent(parent);
	75	}
	76
	77	static bool same_device(struct udev_device a, struct udev_device b) {
	78	assert(a);
	79	assert(b);
	80
	81	if (!streq_ptr(udev_device_get_subsystem(a), udev_device_get_subsystem(b)))
	82	return false;
	83
	84	if (!streq_ptr(udev_device_get_sysname(a), udev_device_get_sysname(b)))
	85	return false;
	86
	87	return true;
	88	}
	89
	90	static bool validate_device(struct udev udev, struct udev_device device) {
8e766630	91	_cleanup_(udev_enumerate_unrefp) struct udev_enumerate *enumerate = NULL;
0f4ba83c LP	92	struct udev_list_entry item = NULL, first = NULL;
	93	struct udev_device *parent;
	94	const char v, subsystem;
	95	int r;
	96
	97	assert(udev);
	98	assert(device);
	99
	100	/* Verify whether we should actually care for a specific
	101	* backlight device. For backlight devices there might be
	102	* multiple ways to access the same control: "firmware"
	103	* (i.e. ACPI), "platform" (i.e. via the machine's EC) and
	104	* "raw" (via the graphics card). In general we should prefer
	105	* "firmware" (i.e. ACPI) or "platform" access over "raw"
	106	* access, in order not to confuse the BIOS/EC, and
	107	* compatibility with possible low-level hotkey handling of
	108	* screen brightness. The kernel will already make sure to
	109	* expose only one of "firmware" and "platform" for the same
	110	* device to userspace. However, we still need to make sure
	111	* that we use "raw" only if no "firmware" or "platform"
	112	* device for the same device exists. */
	113
	114	subsystem = udev_device_get_subsystem(device);
	115	if (!streq_ptr(subsystem, "backlight"))
	116	return true;
	117
	118	v = udev_device_get_sysattr_value(device, "type");
	119	if (!streq_ptr(v, "raw"))
	120	return true;
	121
	122	parent = find_pci_or_platform_parent(device);
	123	if (!parent)
	124	return true;
	125
	126	subsystem = udev_device_get_subsystem(parent);
	127	if (!subsystem)
	128	return true;
	129
	130	enumerate = udev_enumerate_new(udev);
	131	if (!enumerate)
	132	return true;
	133
	134	r = udev_enumerate_add_match_subsystem(enumerate, "backlight");
	135	if (r < 0)
	136	return true;
	137
	138	r = udev_enumerate_scan_devices(enumerate);
	139	if (r < 0)
	140	return true;
	141
	142	first = udev_enumerate_get_list_entry(enumerate);
	143	udev_list_entry_foreach(item, first) {
8e766630	144	_cleanup_(udev_device_unrefp) struct udev_device *other;
0f4ba83c LP	145	struct udev_device *other_parent;
	146	const char *other_subsystem;
	147
	148	other = udev_device_new_from_syspath(udev, udev_list_entry_get_name(item));
	149	if (!other)
	150	return true;
	151
	152	if (same_device(device, other))
	153	continue;
	154
	155	v = udev_device_get_sysattr_value(other, "type");
1cf03a4f	156	if (!STRPTR_IN_SET(v, "platform", "firmware"))
0f4ba83c LP	157	continue;
	158
	159	/* OK, so there's another backlight device, and it's a
	160	* platform or firmware device, so, let's see if we
	161	* can verify it belongs to the same device as
	162	* ours. */
	163	other_parent = find_pci_or_platform_parent(other);
	164	if (!other_parent)
	165	continue;
	166
	167	if (same_device(parent, other_parent)) {
	168	/* Both have the same PCI parent, that means
	169	* we are out. */
938d2699 ZJS	170	log_debug("Skipping backlight device %s, since device %s is on same PCI device and takes precedence.",
	171	udev_device_get_sysname(device),
	172	udev_device_get_sysname(other));
0f4ba83c LP	173	return false;
	174	}
	175
	176	other_subsystem = udev_device_get_subsystem(other_parent);
	177	if (streq_ptr(other_subsystem, "platform") && streq_ptr(subsystem, "pci")) {
	178	/* The other is connected to the platform bus
	179	* and we are a PCI device, that also means we
	180	* are out. */
938d2699 ZJS	181	log_debug("Skipping backlight device %s, since device %s is a platform device and takes precedence.",
	182	udev_device_get_sysname(device),
	183	udev_device_get_sysname(other));
0f4ba83c LP	184	return false;
	185	}
	186	}
	187
	188	return true;
	189	}
	190
3cadce7d	191	static unsigned get_max_brightness(struct udev_device *device) {
7b909d74 JT	192	int r;
7b909d74 JT	193	const char *max_brightness_str;
3cadce7d	194	unsigned max_brightness;
7b909d74 JT	195
	196	max_brightness_str = udev_device_get_sysattr_value(device, "max_brightness");
	197	if (!max_brightness_str) {
c7fdf44d	198	log_warning("Failed to read 'max_brightness' attribute.");
3cadce7d	199	return 0;
7b909d74 JT	200	}
7b909d74 JT	201
3cadce7d	202	r = safe_atou(max_brightness_str, &max_brightness);
7b909d74	203	if (r < 0) {
da927ba9	204	log_warning_errno(r, "Failed to parse 'max_brightness' \"%s\": %m", max_brightness_str);
c7fdf44d LP	205	return 0;
	206	}
	207
	208	if (max_brightness <= 0) {
	209	log_warning("Maximum brightness is 0, ignoring device.");
3cadce7d	210	return 0;
7b909d74 JT	211	}
7b909d74 JT	212
3cadce7d TB	213	return max_brightness;
	214	}
	215
	216	/* Some systems turn the backlight all the way off at the lowest levels.
	217	* clamp_brightness clamps the saved brightness to at least 1 or 5% of
4cd2b2cf DT	218	* max_brightness in case of 'backlight' subsystem. This avoids preserving
	219	* an unreadably dim screen, which would otherwise force the user to
	220	* disable state restoration. */
3cadce7d	221	static void clamp_brightness(struct udev_device device, char *value, unsigned max_brightness) {
0c9d8f1d	222	unsigned brightness, new_brightness, min_brightness;
4cd2b2cf	223	const char *subsystem;
3e44d24d	224	int r;
3cadce7d TB	225
3cadce7d TB	226	r = safe_atou(*value, &brightness);
7b909d74	227	if (r < 0) {
da927ba9	228	log_warning_errno(r, "Failed to parse brightness \"%s\": %m", *value);
7b909d74 JT	229	return;
	230	}
	231
4cd2b2cf DT	232	subsystem = udev_device_get_subsystem(device);
	233	if (streq_ptr(subsystem, "backlight"))
	234	min_brightness = MAX(1U, max_brightness/20);
	235	else
	236	min_brightness = 0;
	237
0c9d8f1d	238	new_brightness = CLAMP(brightness, min_brightness, max_brightness);
7b909d74 JT	239	if (new_brightness != brightness) {
	240	char old_value = value;
	241
	242	r = asprintf(value, "%u", new_brightness);
	243	if (r < 0) {
	244	log_oom();
	245	return;
	246	}
	247
0c9d8f1d JN	248	log_info("Saved brightness %s %s to %s.", old_value,
	249	new_brightness > brightness ?
	250	"too low; increasing" : "too high; decreasing",
	251	*value);
	252
7b909d74 JT	253	free(old_value);
	254	}
	255	}
	256
4432b941 SR	257	static bool shall_clamp(struct udev_device *d) {
	258	const char *s;
	259	int r;
	260
	261	assert(d);
	262
	263	s = udev_device_get_property_value(d, "ID_BACKLIGHT_CLAMP");
	264	if (!s)
	265	return true;
	266
	267	r = parse_boolean(s);
	268	if (r < 0) {
	269	log_debug_errno(r, "Failed to parse ID_BACKLIGHT_CLAMP property, ignoring: %m");
	270	return true;
	271	}
	272
	273	return r;
	274	}
	275
3731acf1	276	int main(int argc, char *argv[]) {
8e766630 LP	277	_cleanup_(udev_unrefp) struct udev *udev = NULL;
8e766630 LP	278	_cleanup_(udev_device_unrefp) struct udev_device *device = NULL;
3e44d24d LP	279	_cleanup_free_ char escaped_ss = NULL, escaped_sysname = NULL, *escaped_path_id = NULL;
3e44d24d LP	280	const char sysname, path_id, ss, saved;
3cadce7d	281	unsigned max_brightness;
3731acf1 LP	282	int r;
	283
	284	if (argc != 3) {
	285	log_error("This program requires two arguments.");
	286	return EXIT_FAILURE;
	287	}
	288
	289	log_set_target(LOG_TARGET_AUTO);
	290	log_parse_environment();
	291	log_open();
	292
	293	umask(0022);
	294
ef5bfcf6	295	r = mkdir_p("/var/lib/systemd/backlight", 0755);
3731acf1	296	if (r < 0) {
c33b3297	297	log_error_errno(r, "Failed to create backlight directory /var/lib/systemd/backlight: %m");
1ca208fb	298	return EXIT_FAILURE;
3731acf1 LP	299	}
	300
	301	udev = udev_new();
	302	if (!udev) {
1ca208fb ZJS	303	log_oom();
1ca208fb ZJS	304	return EXIT_FAILURE;
3731acf1 LP	305	}
3731acf1 LP	306
0f4ba83c LP	307	sysname = strchr(argv[2], ':');
0f4ba83c LP	308	if (!sysname) {
938d2699	309	log_error("Requires a subsystem and sysname pair specifying a backlight device.");
0f4ba83c LP	310	return EXIT_FAILURE;
	311	}
	312
3e44d24d	313	ss = strndupa(argv[2], sysname - argv[2]);
0f4ba83c LP	314
	315	sysname++;
	316
3e44d24d	317	if (!STR_IN_SET(ss, "backlight", "leds")) {
0f4ba83c LP	318	log_error("Not a backlight or LED device: '%s:%s'", ss, sysname);
	319	return EXIT_FAILURE;
	320	}
	321
875c6e1b	322	errno = 0;
0f4ba83c	323	device = udev_device_new_from_subsystem_sysname(udev, ss, sysname);
3731acf1	324	if (!device) {
b3267152	325	if (errno > 0)
56f64d95	326	log_error_errno(errno, "Failed to get backlight or LED device '%s:%s': %m", ss, sysname);
1ca208fb	327	else
0f4ba83c	328	log_oom();
3731acf1	329
1ca208fb	330	return EXIT_FAILURE;
3731acf1 LP	331	}
3731acf1 LP	332
3cadce7d TB	333	/* If max_brightness is 0, then there is no actual backlight
	334	* device. This happens on desktops with Asus mainboards
	335	* that load the eeepc-wmi module.
	336	*/
	337	max_brightness = get_max_brightness(device);
	338	if (max_brightness == 0)
	339	return EXIT_SUCCESS;
	340
be3f52f4 LP	341	escaped_ss = cescape(ss);
	342	if (!escaped_ss) {
	343	log_oom();
	344	return EXIT_FAILURE;
	345	}
	346
	347	escaped_sysname = cescape(sysname);
	348	if (!escaped_sysname) {
	349	log_oom();
	350	return EXIT_FAILURE;
	351	}
	352
	353	path_id = udev_device_get_property_value(device, "ID_PATH");
	354	if (path_id) {
	355	escaped_path_id = cescape(path_id);
	356	if (!escaped_path_id) {
	357	log_oom();
	358	return EXIT_FAILURE;
	359	}
	360
3e44d24d	361	saved = strjoina("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_ss, ":", escaped_sysname);
be3f52f4	362	} else
3e44d24d	363	saved = strjoina("/var/lib/systemd/backlight/", escaped_ss, ":", escaped_sysname);
3731acf1	364
0f4ba83c LP	365	/* If there are multiple conflicting backlight devices, then
	366	* their probing at boot-time might happen in any order. This
	367	* means the validity checking of the device then is not
	368	* reliable, since it might not see other devices conflicting
73e231ab	369	* with a specific backlight. To deal with this, we will
0f4ba83c LP	370	* actively delete backlight state files at shutdown (where
	371	* device probing should be complete), so that the validity
	372	* check at boot time doesn't have to be reliable. */
	373
b76388e1	374	if (streq(argv[1], "load")) {
3731acf1	375	_cleanup_free_ char *value = NULL;
4432b941	376	bool clamp;
3731acf1	377
934ae16b	378	if (shall_restore_state() == 0)
b76388e1 MB	379	return EXIT_SUCCESS;
b76388e1 MB	380
0f4ba83c LP	381	if (!validate_device(udev, device))
	382	return EXIT_SUCCESS;
	383
4432b941 SR	384	clamp = shall_clamp(device);
4432b941 SR	385
3731acf1	386	r = read_one_line_file(saved, &value);
4432b941 SR	387	if (r == -ENOENT) {
4432b941 SR	388	const char *curval;
3731acf1	389
4432b941 SR	390	/* Fallback to clamping current brightness or exit early if
	391	* clamping is not supported/enabled. */
	392	if (!clamp)
1ca208fb	393	return EXIT_SUCCESS;
3731acf1	394
4432b941 SR	395	curval = udev_device_get_sysattr_value(device, "brightness");
	396	if (!curval) {
	397	log_warning("Failed to read 'brightness' attribute.");
	398	return EXIT_FAILURE;
	399	}
	400
	401	value = strdup(curval);
	402	if (!value) {
	403	log_oom();
	404	return EXIT_FAILURE;
	405	}
	406	} else if (r < 0) {
da927ba9	407	log_error_errno(r, "Failed to read %s: %m", saved);
1ca208fb	408	return EXIT_FAILURE;
3731acf1 LP	409	}
3731acf1 LP	410
4432b941	411	if (clamp)
bca81be7	412	clamp_brightness(device, &value, max_brightness);
7b909d74	413
3731acf1 LP	414	r = udev_device_set_sysattr_value(device, "brightness", value);
3731acf1 LP	415	if (r < 0) {
c33b3297	416	log_error_errno(r, "Failed to write system 'brightness' attribute: %m");
1ca208fb	417	return EXIT_FAILURE;
3731acf1 LP	418	}
	419
	420	} else if (streq(argv[1], "save")) {
	421	const char *value;
	422
0f4ba83c LP	423	if (!validate_device(udev, device)) {
	424	unlink(saved);
	425	return EXIT_SUCCESS;
	426	}
	427
3731acf1 LP	428	value = udev_device_get_sysattr_value(device, "brightness");
3731acf1 LP	429	if (!value) {
938d2699	430	log_error("Failed to read system 'brightness' attribute");
1ca208fb	431	return EXIT_FAILURE;
3731acf1 LP	432	}
3731acf1 LP	433
4c1fc3e4	434	r = write_string_file(saved, value, WRITE_STRING_FILE_CREATE);
3731acf1	435	if (r < 0) {
da927ba9	436	log_error_errno(r, "Failed to write %s: %m", saved);
1ca208fb	437	return EXIT_FAILURE;
3731acf1 LP	438	}
	439
	440	} else {
	441	log_error("Unknown verb %s.", argv[1]);
1ca208fb	442	return EXIT_FAILURE;
3731acf1 LP	443	}
3731acf1 LP	444
1ca208fb	445	return EXIT_SUCCESS;
3731acf1	446	}