/* SPDX-License-Identifier: LGPL-2.1+ */ #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; }