1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
4 This file is part of systemd.
6 Copyright 2013 Lennart Poettering
8 systemd is free software; you can redistribute it and/or modify it
9 under the terms of the GNU Lesser General Public License as published by
10 the Free Software Foundation; either version 2.1 of the License, or
11 (at your option) any later version.
13 systemd is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 Lesser General Public License for more details.
18 You should have received a copy of the GNU Lesser General Public License
19 along with systemd; If not, see <http://www.gnu.org/licenses/>.
26 #include "udev-util.h"
28 static struct udev_device *find_pci_or_platform_parent(struct udev_device *device) {
29 struct udev_device *parent;
30 const char *subsystem, *sysname;
34 parent = udev_device_get_parent(device);
38 subsystem = udev_device_get_subsystem(parent);
42 sysname = udev_device_get_sysname(parent);
46 if (streq(subsystem, "drm")) {
49 c = startswith(sysname, "card");
53 c += strspn(c, "0123456789");
55 /* A connector DRM device, let's ignore all but LVDS and eDP! */
57 if (!startswith(c, "-LVDS-") &&
58 !startswith(c, "-Embedded DisplayPort-"))
62 } else if (streq(subsystem, "pci")) {
65 value = udev_device_get_sysattr_value(parent, "class");
69 if (safe_atolu(value, &class) < 0) {
70 log_warning("Cannot parse PCI class %s of device %s:%s.", value, subsystem, sysname);
79 } else if (streq(subsystem, "platform"))
82 return find_pci_or_platform_parent(parent);
85 static bool same_device(struct udev_device *a, struct udev_device *b) {
89 if (!streq_ptr(udev_device_get_subsystem(a), udev_device_get_subsystem(b)))
92 if (!streq_ptr(udev_device_get_sysname(a), udev_device_get_sysname(b)))
98 static bool validate_device(struct udev *udev, struct udev_device *device) {
99 _cleanup_udev_enumerate_unref_ struct udev_enumerate *enumerate = NULL;
100 struct udev_list_entry *item = NULL, *first = NULL;
101 struct udev_device *parent;
102 const char *v, *subsystem;
108 /* Verify whether we should actually care for a specific
109 * backlight device. For backlight devices there might be
110 * multiple ways to access the same control: "firmware"
111 * (i.e. ACPI), "platform" (i.e. via the machine's EC) and
112 * "raw" (via the graphics card). In general we should prefer
113 * "firmware" (i.e. ACPI) or "platform" access over "raw"
114 * access, in order not to confuse the BIOS/EC, and
115 * compatibility with possible low-level hotkey handling of
116 * screen brightness. The kernel will already make sure to
117 * expose only one of "firmware" and "platform" for the same
118 * device to userspace. However, we still need to make sure
119 * that we use "raw" only if no "firmware" or "platform"
120 * device for the same device exists. */
122 subsystem = udev_device_get_subsystem(device);
123 if (!streq_ptr(subsystem, "backlight"))
126 v = udev_device_get_sysattr_value(device, "type");
127 if (!streq_ptr(v, "raw"))
130 parent = find_pci_or_platform_parent(device);
134 subsystem = udev_device_get_subsystem(parent);
138 enumerate = udev_enumerate_new(udev);
142 r = udev_enumerate_add_match_subsystem(enumerate, "backlight");
146 r = udev_enumerate_scan_devices(enumerate);
150 first = udev_enumerate_get_list_entry(enumerate);
151 udev_list_entry_foreach(item, first) {
152 _cleanup_udev_device_unref_ struct udev_device *other;
153 struct udev_device *other_parent;
154 const char *other_subsystem;
156 other = udev_device_new_from_syspath(udev, udev_list_entry_get_name(item));
160 if (same_device(device, other))
163 v = udev_device_get_sysattr_value(other, "type");
164 if (!streq_ptr(v, "platform") && !streq_ptr(v, "firmware"))
167 /* OK, so there's another backlight device, and it's a
168 * platform or firmware device, so, let's see if we
169 * can verify it belongs to the same device as
171 other_parent = find_pci_or_platform_parent(other);
175 if (same_device(parent, other_parent)) {
176 /* Both have the same PCI parent, that means
178 log_debug("Skipping backlight device %s, since backlight device %s is on same PCI device and, takes precedence.", udev_device_get_sysname(device), udev_device_get_sysname(other));
182 other_subsystem = udev_device_get_subsystem(other_parent);
183 if (streq_ptr(other_subsystem, "platform") && streq_ptr(subsystem, "pci")) {
184 /* The other is connected to the platform bus
185 * and we are a PCI device, that also means we
187 log_debug("Skipping backlight device %s, since backlight device %s is a platform device and takes precedence.", udev_device_get_sysname(device), udev_device_get_sysname(other));
195 int main(int argc, char *argv[]) {
196 _cleanup_udev_unref_ struct udev *udev = NULL;
197 _cleanup_udev_device_unref_ struct udev_device *device = NULL;
198 _cleanup_free_ char *saved = NULL, *ss = NULL, *escaped_ss = NULL, *escaped_sysname = NULL, *escaped_path_id = NULL;
199 const char *sysname, *path_id;
203 log_error("This program requires two arguments.");
207 log_set_target(LOG_TARGET_AUTO);
208 log_parse_environment();
213 r = mkdir_p("/var/lib/systemd/backlight", 0755);
215 log_error("Failed to create backlight directory: %s", strerror(-r));
225 sysname = strchr(argv[2], ':');
227 log_error("Requires pair of subsystem and sysname for specifying backlight device.");
231 ss = strndup(argv[2], sysname - argv[2]);
239 if (!streq(ss, "backlight") && !streq(ss, "leds")) {
240 log_error("Not a backlight or LED device: '%s:%s'", ss, sysname);
245 device = udev_device_new_from_subsystem_sysname(udev, ss, sysname);
248 log_error("Failed to get backlight or LED device '%s:%s': %m", ss, sysname);
255 escaped_ss = cescape(ss);
261 escaped_sysname = cescape(sysname);
262 if (!escaped_sysname) {
267 path_id = udev_device_get_property_value(device, "ID_PATH");
269 escaped_path_id = cescape(path_id);
270 if (!escaped_path_id) {
275 saved = strjoin("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_ss, ":", escaped_sysname, NULL);
277 saved = strjoin("/var/lib/systemd/backlight/", escaped_ss, ":", escaped_sysname, NULL);
284 /* If there are multiple conflicting backlight devices, then
285 * their probing at boot-time might happen in any order. This
286 * means the validity checking of the device then is not
287 * reliable, since it might not see other devices conflicting
288 * with a specific backlight. To deal with this we will
289 * actively delete backlight state files at shutdown (where
290 * device probing should be complete), so that the validity
291 * check at boot time doesn't have to be reliable. */
293 if (streq(argv[1], "load") && shall_restore_state()) {
294 _cleanup_free_ char *value = NULL;
296 if (!validate_device(udev, device))
299 r = read_one_line_file(saved, &value);
305 log_error("Failed to read %s: %s", saved, strerror(-r));
309 r = udev_device_set_sysattr_value(device, "brightness", value);
311 log_error("Failed to write system attribute: %s", strerror(-r));
315 } else if (streq(argv[1], "save")) {
318 if (!validate_device(udev, device)) {
323 value = udev_device_get_sysattr_value(device, "brightness");
325 log_error("Failed to read system attribute: %s", strerror(-r));
329 r = write_string_file(saved, value);
331 log_error("Failed to write %s: %s", saved, strerror(-r));
336 log_error("Unknown verb %s.", argv[1]);