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main
src/backlight/backlight.c
653 строки
23 KB
Yu Watanabe
tree-wide: use device_get_sysattr_unsigned() and friends
17 май 2026, 20:55
17 май 2026, 20:55
6f72bb7
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/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include <sys/stat.h> #include <unistd.h> #include "sd-device.h" #include "alloc-util.h" #include "argv-util.h" #include "device-private.h" #include "device-util.h" #include "escape.h" #include "fileio.h" #include "format-table.h" #include "help-util.h" #include "main-func.h" #include "parse-util.h" #include "percent-util.h" #include "reboot-util.h" #include "string-util.h" #include "strv.h" #include "verbs.h" #define PCI_CLASS_GRAPHICS_CARD 0x30000 static int help(void) { _cleanup_(table_unrefp) Table *verbs = NULL; int r; r = verbs_get_help_table(&verbs); if (r < 0) return r; help_cmdline("COMMAND [backlight|leds]:DEVICE"); help_abstract("Save and restore backlight brightness at shutdown and boot."); help_section("Commands"); r = table_print_or_warn(verbs); if (r < 0) return r; help_man_page_reference("systemd-backlight", "8"); return 0; } static int has_multiple_graphics_cards(void) { _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL; bool found = false; int r; r = sd_device_enumerator_new(&e); if (r < 0) return r; r = sd_device_enumerator_allow_uninitialized(e); if (r < 0) return r; r = sd_device_enumerator_add_match_subsystem(e, "pci", /* match= */ true); if (r < 0) return r; /* class is an unsigned number, let's validate the value later. */ r = sd_device_enumerator_add_match_sysattr(e, "class", NULL, /* match= */ true); if (r < 0) return r; FOREACH_DEVICE(e, dev) { uint32_t c; if (device_get_sysattr_u32(dev, "class", &c) < 0) continue; if (c != PCI_CLASS_GRAPHICS_CARD) continue; if (found) return true; /* This is the second device. */ found = true; /* Found the first device. */ } return false; } static int find_pci_or_platform_parent(sd_device *device, sd_device **ret) { int r; assert(device); assert(ret); for (;;) { r = sd_device_get_parent(device, &device); if (r < 0) return r; r = device_in_subsystem(device, "drm"); if (r < 0) return r; if (r > 0) { const char *s; r = device_sysname_startswith_strv(device, STRV_MAKE("card"), &s); if (r < 0) return r; if (r == 0) return -ENODATA; s += strspn(s, DIGITS); if (*s == '-' && !STARTSWITH_SET(s, "-LVDS-", "-Embedded DisplayPort-", "-eDP-")) /* A connector DRM device, let's ignore all but LVDS and eDP! */ return -EOPNOTSUPP; continue; } r = device_in_subsystem(device, "pci"); if (r < 0) return r; if (r > 0) { uint32_t class; r = device_get_sysattr_u32(device, "class", &class); if (r == -ENOENT) continue; if (r < 0) return r; /* Graphics card */ if (class == PCI_CLASS_GRAPHICS_CARD) { *ret = device; return 0; } continue; } r = device_in_subsystem(device, "platform"); if (r < 0) return r; if (r > 0) { *ret = device; return 0; } } } static int same_device(sd_device *a, sd_device *b) { const char *a_val, *b_val; int r; assert(a); assert(b); r = sd_device_get_subsystem(a, &a_val); if (r < 0) return r; r = sd_device_get_subsystem(b, &b_val); if (r < 0) return r; if (!streq(a_val, b_val)) return false; r = sd_device_get_sysname(a, &a_val); if (r < 0) return r; r = sd_device_get_sysname(b, &b_val); if (r < 0) return r; return streq(a_val, b_val); } static int validate_device(sd_device *device) { _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *enumerate = NULL; const char *sysname; sd_device *parent; int r; 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. */ r = sd_device_get_sysname(device, &sysname); if (r < 0) return log_device_debug_errno(device, r, "Failed to get sysname: %m"); r = device_in_subsystem(device, "leds"); if (r < 0) return log_device_debug_errno(device, r, "Failed to check if device is in leds subsystem: %m"); if (r > 0) return true; /* We assume LED device is always valid. */ r = device_get_sysattr_streq(device, "type", "raw"); if (r < 0) return log_device_debug_errno(device, r, "Failed to read 'type' sysattr: %m"); if (r == 0) return true; r = find_pci_or_platform_parent(device, &parent); if (r < 0) return log_device_debug_errno(device, r, "Failed to find PCI or platform parent: %m"); if (DEBUG_LOGGING) { const char *s = NULL, *subsystem = NULL; (void) sd_device_get_syspath(parent, &s); (void) sd_device_get_subsystem(parent, &subsystem); log_device_debug(device, "Found %s parent device: %s", strna(subsystem), strna(s)); } r = sd_device_enumerator_new(&enumerate); if (r < 0) return log_oom_debug(); r = sd_device_enumerator_allow_uninitialized(enumerate); if (r < 0) return log_debug_errno(r, "Failed to allow uninitialized devices: %m"); r = sd_device_enumerator_add_match_subsystem(enumerate, "backlight", /* match= */ true); if (r < 0) return log_debug_errno(r, "Failed to add subsystem match: %m"); r = sd_device_enumerator_add_nomatch_sysname(enumerate, sysname); if (r < 0) return log_debug_errno(r, "Failed to add sysname unmatch: %m"); r = sd_device_enumerator_add_match_sysattr(enumerate, "type", "platform", /* match= */ true); if (r < 0) return log_debug_errno(r, "Failed to add sysattr match: %m"); r = sd_device_enumerator_add_match_sysattr(enumerate, "type", "firmware", /* match= */ true); if (r < 0) return log_debug_errno(r, "Failed to add sysattr match: %m"); if (device_in_subsystem(parent, "pci") > 0) { r = has_multiple_graphics_cards(); if (r < 0) return log_debug_errno(r, "Failed to check if the system has multiple graphics cards: %m"); if (r > 0) { /* If the system has multiple graphics cards, then we cannot associate platform * devices on non-PCI bus (especially WMI bus) with PCI devices. Let's ignore all * backlight devices that do not have the same parent PCI device. */ log_debug("Found multiple graphics cards on PCI bus; " "skipping deduplication of platform backlight devices not on PCI bus."); r = sd_device_enumerator_add_match_parent(enumerate, parent); if (r < 0) return log_debug_errno(r, "Failed to add parent match: %m"); } } FOREACH_DEVICE(enumerate, other) { sd_device *other_parent; /* OK, so there's another backlight device, and it's a platform or firmware device. * Let's see if we can verify it belongs to the same device as ours. */ r = find_pci_or_platform_parent(other, &other_parent); if (r < 0) { log_device_debug_errno(other, r, "Failed to get PCI or platform parent, ignoring: %m"); continue; } if (same_device(parent, other_parent) > 0) { /* Both have the same PCI parent, that means we are out. */ if (DEBUG_LOGGING) { const char *other_sysname = NULL, *other_type = NULL; (void) sd_device_get_sysname(other, &other_sysname); (void) device_get_sysattr_safe_string(other, "type", &other_type); log_device_debug(device, "Found another %s backlight device %s on the same PCI, skipping.", strna(other_type), strna(other_sysname)); } return false; } if (device_in_subsystem(other_parent, "platform") > 0 && device_in_subsystem(parent, "pci") > 0) { /* The other is connected to the platform bus and we are a PCI device, that also means we are out. */ if (DEBUG_LOGGING) { const char *other_sysname = NULL, *other_type = NULL; (void) sd_device_get_sysname(other, &other_sysname); (void) device_get_sysattr_safe_string(other, "type", &other_type); log_device_debug(device, "Found another %s backlight device %s, which has higher precedence, skipping.", strna(other_type), strna(other_sysname)); } return false; } } return true; } static int read_max_brightness(sd_device *device, unsigned *ret) { unsigned max_brightness; int r; assert(device); assert(ret); r = device_get_sysattr_unsigned(device, "max_brightness", &max_brightness); if (r < 0) return log_device_warning_errno(device, r, "Failed to read 'max_brightness' attribute: %m"); /* 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. */ if (max_brightness == 0) { log_device_warning(device, "Maximum brightness is 0, ignoring device."); *ret = 0; return 0; } log_device_debug(device, "Maximum brightness is %u", max_brightness); *ret = max_brightness; return 1; /* valid max brightness */ } static int clamp_brightness( sd_device *device, unsigned percent, bool saved, unsigned max_brightness, unsigned *brightness) { unsigned new_brightness, min_brightness; int r; assert(device); assert(brightness); /* Some systems turn the backlight all the way off at the lowest levels. This clamps the saved * brightness to at least 1 or 1% of max_brightness (whichever is bigger) in case of 'backlight' subsystem. * This avoids preserving an unreadably dim screen, which would otherwise force the user to disable * state restoration. */ min_brightness = (unsigned) ((double) max_brightness * percent / 100); r = device_in_subsystem(device, "backlight"); if (r < 0) return r; if (r > 0) min_brightness = MAX(1U, min_brightness); new_brightness = CLAMP(*brightness, min_brightness, max_brightness); if (new_brightness != *brightness) log_device_info(device, "%s brightness %u is %s to %u.", saved ? "Saved" : "Current", *brightness, new_brightness > *brightness ? "too low; increasing" : "too high; decreasing", new_brightness); *brightness = new_brightness; return 0; } /* used as the default for devices in the backlight subsystem, or when ID_BACKLIGHT_CLAMP/ID_LEDS_CLAMP=yes. */ #define DEFAULT_CLAMP_PERCENT 1u static int shall_clamp(sd_device *device, unsigned *ret) { const char *property, *s; unsigned default_percent; int r; assert(device); assert(ret); r = device_in_subsystem(device, "backlight"); if (r < 0) return r; if (r > 0) { property = "ID_BACKLIGHT_CLAMP"; default_percent = DEFAULT_CLAMP_PERCENT; } else { property = "ID_LEDS_CLAMP"; default_percent = 0; /* The clamping is disabled by default. */ } r = sd_device_get_property_value(device, property, &s); if (r < 0) { if (r != -ENOENT) log_device_debug_errno(device, r, "Failed to get %s property, ignoring: %m", property); *ret = default_percent; return default_percent > 0; } r = parse_boolean(s); if (r >= 0) { *ret = r ? DEFAULT_CLAMP_PERCENT : 0; return r; } r = parse_percent(s); if (r < 0) { log_device_debug_errno(device, r, "Failed to parse %s property, ignoring: %m", property); *ret = default_percent; return default_percent > 0; } *ret = r; return true; } static int read_brightness(sd_device *device, unsigned max_brightness, unsigned *ret_brightness) { unsigned brightness; int r; assert(device); assert(ret_brightness); r = device_get_sysattr_unsigned(device, "brightness", &brightness); if (r < 0) return log_device_debug_errno(device, r, "Failed to read 'brightness' attribute: %m"); if (brightness > max_brightness) return log_device_debug_errno(device, SYNTHETIC_ERRNO(EINVAL), "brightness=%u is larger than max_brightness=%u", brightness, max_brightness); log_device_debug(device, "Current brightness is %u", brightness); *ret_brightness = brightness; return 0; } static int build_save_file_path(sd_device *device, char **ret) { _cleanup_free_ char *escaped_subsystem = NULL, *escaped_sysname = NULL, *path = NULL; const char *s; int r; assert(device); assert(ret); r = sd_device_get_subsystem(device, &s); if (r < 0) return log_device_error_errno(device, r, "Failed to get subsystem: %m"); escaped_subsystem = cescape(s); if (!escaped_subsystem) return log_oom(); r = sd_device_get_sysname(device, &s); if (r < 0) return log_device_error_errno(device, r, "Failed to get sysname: %m"); escaped_sysname = cescape(s); if (!escaped_sysname) return log_oom(); if (sd_device_get_property_value(device, "ID_PATH", &s) >= 0) { _cleanup_free_ char *escaped_path_id = cescape(s); if (!escaped_path_id) return log_oom(); path = strjoin("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_subsystem, ":", escaped_sysname); } else path = strjoin("/var/lib/systemd/backlight/", escaped_subsystem, ":", escaped_sysname); if (!path) return log_oom(); *ret = TAKE_PTR(path); return 0; } static int read_saved_brightness(sd_device *device, unsigned *ret) { _cleanup_free_ char *path = NULL, *value = NULL; int r; assert(device); assert(ret); r = build_save_file_path(device, &path); if (r < 0) return r; r = read_one_line_file(path, &value); if (r < 0) { if (r != -ENOENT) log_device_error_errno(device, r, "Failed to read %s: %m", path); return r; } r = safe_atou(value, ret); if (r < 0) { log_device_warning_errno(device, r, "Failed to parse saved brightness '%s', removing %s.", value, path); (void) unlink(path); return r; } log_device_debug(device, "Using saved brightness %u.", *ret); return 0; } static int device_new_from_arg(const char *s, sd_device **ret) { _cleanup_(sd_device_unrefp) sd_device *device = NULL; _cleanup_free_ char *subsystem = NULL; const char *sysname; int r; assert(s); assert(ret); sysname = strchr(s, ':'); if (!sysname) return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Requires a subsystem and sysname pair specifying a backlight or LED device."); subsystem = strndup(s, sysname - s); if (!subsystem) return log_oom(); sysname++; if (!STR_IN_SET(subsystem, "backlight", "leds")) return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Not a backlight or LED device: '%s:%s'", subsystem, sysname); r = sd_device_new_from_subsystem_sysname(&device, subsystem, sysname); if (r == -ENODEV) { /* Some drivers, e.g. for AMD GPU, removes acpi backlight device soon after it is added. * See issue #21997. */ log_debug_errno(r, "Failed to get backlight or LED device '%s:%s', ignoring: %m", subsystem, sysname); *ret = NULL; return 0; } if (r < 0) return log_error_errno(r, "Failed to get backlight or LED device '%s:%s': %m", subsystem, sysname); *ret = TAKE_PTR(device); return 1; /* Found. */ } VERB(verb_load, "load", "[backlight|leds]:DEVICE", 2, 2, VERB_ONLINE_ONLY, "Set brightness to be the previously saved value"); static int verb_load(int argc, char *argv[], uintptr_t _data, void *userdata) { _cleanup_(sd_device_unrefp) sd_device *device = NULL; unsigned max_brightness, brightness, percent; bool clamp; int r; assert(argc == 2); if (!shall_restore_state()) return 0; r = device_new_from_arg(argv[1], &device); if (r <= 0) return r; r = read_max_brightness(device, &max_brightness); if (r <= 0) return r; /* Ignore any errors in validation, and use the device as is. */ if (validate_device(device) == 0) return 0; r = shall_clamp(device, &percent); if (r < 0) return r; clamp = r; r = read_saved_brightness(device, &brightness); if (r < 0) { /* Fallback to clamping current brightness or exit early if clamping is not * supported/enabled. */ if (!clamp) return 0; r = read_brightness(device, max_brightness, &brightness); if (r < 0) return log_device_error_errno(device, r, "Failed to read current brightness: %m"); (void) clamp_brightness(device, percent, /* saved= */ false, max_brightness, &brightness); } else if (clamp) (void) clamp_brightness(device, percent, /* saved= */ true, max_brightness, &brightness); r = sd_device_set_sysattr_valuef(device, "brightness", "%u", brightness); if (r < 0) return log_device_error_errno(device, r, "Failed to write system 'brightness' attribute: %m"); return 0; } VERB(verb_save, "save", "[backlight|leds]:DEVICE", 2, 2, VERB_ONLINE_ONLY, "Save current brightness"); static int verb_save(int argc, char *argv[], uintptr_t _data, void *userdata) { _cleanup_(sd_device_unrefp) sd_device *device = NULL; _cleanup_free_ char *path = NULL; unsigned max_brightness, brightness; int r; assert(argc == 2); r = device_new_from_arg(argv[1], &device); if (r <= 0) return r; r = read_max_brightness(device, &max_brightness); if (r <= 0) return r; r = build_save_file_path(device, &path); if (r < 0) return r; /* 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 (validate_device(device) == 0) { (void) unlink(path); return 0; } r = read_brightness(device, max_brightness, &brightness); if (r < 0) return log_device_error_errno(device, r, "Failed to read current brightness: %m"); r = write_string_filef(path, WRITE_STRING_FILE_CREATE | WRITE_STRING_FILE_MKDIR_0755, "%u", brightness); if (r < 0) return log_device_error_errno(device, r, "Failed to write %s: %m", path); return 0; } static int run(int argc, char *argv[]) { log_setup(); if (argv_looks_like_help(argc, argv)) return help(); umask(0022); return dispatch_verb(strv_skip(argv, 1), /* userdata= */ NULL); } DEFINE_MAIN_FUNCTION(run);