src/backlight/backlight.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2013 Lennart Poettering
   7
   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.
  12
  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.
  17
  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/>.
  20 ***/
  21
  22 #include "util.h"
  23 #include "mkdir.h"
  24 #include "fileio.h"
  25 #include "libudev.h"
  26 #include "udev-util.h"
  27 #include "def.h"
  28
  29 static struct udev_device *find_pci_or_platform_parent(struct udev_device *device) {
  30         struct udev_device *parent;
  31         const char *subsystem, *sysname;
  32
  33         assert(device);
  34
  35         parent = udev_device_get_parent(device);
  36         if (!parent)
  37                 return NULL;
  38
  39         subsystem = udev_device_get_subsystem(parent);
  40         if (!subsystem)
  41                 return NULL;
  42
  43         sysname = udev_device_get_sysname(parent);
  44         if (!sysname)
  45                 return NULL;
  46
  47         if (streq(subsystem, "drm")) {
  48                 const char *c;
  49
  50                 c = startswith(sysname, "card");
  51                 if (!c)
  52                         return NULL;
  53
  54                 c += strspn(c, DIGITS);
  55                 if (*c == '-') {
  56                         /* A connector DRM device, let's ignore all but LVDS and eDP! */
  57
  58                         if (!startswith(c, "-LVDS-") &&
  59                             !startswith(c, "-Embedded DisplayPort-"))
  60                                 return NULL;
  61                 }
  62
  63         } else if (streq(subsystem, "pci")) {
  64                 const char *value;
  65
  66                 value = udev_device_get_sysattr_value(parent, "class");
  67                 if (value) {
  68                         unsigned long class = 0;
  69
  70                         if (safe_atolu(value, &class) < 0) {
  71                                 log_warning("Cannot parse PCI class %s of device %s:%s.",
  72                                             value, subsystem, sysname);
  73                                 return NULL;
  74                         }
  75
  76                         /* Graphics card */
  77                         if (class == 0x30000)
  78                                 return parent;
  79                 }
  80
  81         } else if (streq(subsystem, "platform"))
  82                 return parent;
  83
  84         return find_pci_or_platform_parent(parent);
  85 }
  86
  87 static bool same_device(struct udev_device *a, struct udev_device *b) {
  88         assert(a);
  89         assert(b);
  90
  91         if (!streq_ptr(udev_device_get_subsystem(a), udev_device_get_subsystem(b)))
  92                 return false;
  93
  94         if (!streq_ptr(udev_device_get_sysname(a), udev_device_get_sysname(b)))
  95                 return false;
  96
  97         return true;
  98 }
  99
 100 static bool validate_device(struct udev *udev, struct udev_device *device) {
 101         _cleanup_udev_enumerate_unref_ struct udev_enumerate *enumerate = NULL;
 102         struct udev_list_entry *item = NULL, *first = NULL;
 103         struct udev_device *parent;
 104         const char *v, *subsystem;
 105         int r;
 106
 107         assert(udev);
 108         assert(device);
 109
 110         /* Verify whether we should actually care for a specific
 111          * backlight device. For backlight devices there might be
 112          * multiple ways to access the same control: "firmware"
 113          * (i.e. ACPI), "platform" (i.e. via the machine's EC) and
 114          * "raw" (via the graphics card). In general we should prefer
 115          * "firmware" (i.e. ACPI) or "platform" access over "raw"
 116          * access, in order not to confuse the BIOS/EC, and
 117          * compatibility with possible low-level hotkey handling of
 118          * screen brightness. The kernel will already make sure to
 119          * expose only one of "firmware" and "platform" for the same
 120          * device to userspace. However, we still need to make sure
 121          * that we use "raw" only if no "firmware" or "platform"
 122          * device for the same device exists. */
 123
 124         subsystem = udev_device_get_subsystem(device);
 125         if (!streq_ptr(subsystem, "backlight"))
 126                 return true;
 127
 128         v = udev_device_get_sysattr_value(device, "type");
 129         if (!streq_ptr(v, "raw"))
 130                 return true;
 131
 132         parent = find_pci_or_platform_parent(device);
 133         if (!parent)
 134                 return true;
 135
 136         subsystem = udev_device_get_subsystem(parent);
 137         if (!subsystem)
 138                 return true;
 139
 140         enumerate = udev_enumerate_new(udev);
 141         if (!enumerate)
 142                 return true;
 143
 144         r = udev_enumerate_add_match_subsystem(enumerate, "backlight");
 145         if (r < 0)
 146                 return true;
 147
 148         r = udev_enumerate_scan_devices(enumerate);
 149         if (r < 0)
 150                 return true;
 151
 152         first = udev_enumerate_get_list_entry(enumerate);
 153         udev_list_entry_foreach(item, first) {
 154                 _cleanup_udev_device_unref_ struct udev_device *other;
 155                 struct udev_device *other_parent;
 156                 const char *other_subsystem;
 157
 158                 other = udev_device_new_from_syspath(udev, udev_list_entry_get_name(item));
 159                 if (!other)
 160                         return true;
 161
 162                 if (same_device(device, other))
 163                         continue;
 164
 165                 v = udev_device_get_sysattr_value(other, "type");
 166                 if (!streq_ptr(v, "platform") && !streq_ptr(v, "firmware"))
 167                         continue;
 168
 169                 /* OK, so there's another backlight device, and it's a
 170                  * platform or firmware device, so, let's see if we
 171                  * can verify it belongs to the same device as
 172                  * ours. */
 173                 other_parent = find_pci_or_platform_parent(other);
 174                 if (!other_parent)
 175                         continue;
 176
 177                 if (same_device(parent, other_parent)) {
 178                         /* Both have the same PCI parent, that means
 179                          * we are out. */
 180                         log_debug("Skipping backlight device %s, since device %s is on same PCI device and takes precedence.",
 181                                   udev_device_get_sysname(device),
 182                                   udev_device_get_sysname(other));
 183                         return false;
 184                 }
 185
 186                 other_subsystem = udev_device_get_subsystem(other_parent);
 187                 if (streq_ptr(other_subsystem, "platform") && streq_ptr(subsystem, "pci")) {
 188                         /* The other is connected to the platform bus
 189                          * and we are a PCI device, that also means we
 190                          * are out. */
 191                         log_debug("Skipping backlight device %s, since device %s is a platform device and takes precedence.",
 192                                   udev_device_get_sysname(device),
 193                                   udev_device_get_sysname(other));
 194                         return false;
 195                 }
 196         }
 197
 198         return true;
 199 }
 200
 201 static unsigned get_max_brightness(struct udev_device *device) {
 202         int r;
 203         const char *max_brightness_str;
 204         unsigned max_brightness;
 205
 206         max_brightness_str = udev_device_get_sysattr_value(device, "max_brightness");
 207         if (!max_brightness_str) {
 208                 log_warning("Failed to read 'max_brightness' attribute.");
 209                 return 0;
 210         }
 211
 212         r = safe_atou(max_brightness_str, &max_brightness);
 213         if (r < 0) {
 214                 log_warning("Failed to parse 'max_brightness' \"%s\": %s", max_brightness_str, strerror(-r));
 215                 return 0;
 216         }
 217
 218         if (max_brightness <= 0) {
 219                 log_warning("Maximum brightness is 0, ignoring device.");
 220                 return 0;
 221         }
 222
 223         return max_brightness;
 224 }
 225
 226 /* Some systems turn the backlight all the way off at the lowest levels.
 227  * clamp_brightness clamps the saved brightness to at least 1 or 5% of
 228  * max_brightness.  This avoids preserving an unreadably dim screen, which
 229  * would otherwise force the user to disable state restoration. */
 230 static void clamp_brightness(struct udev_device *device, char **value, unsigned max_brightness) {
 231         int r;
 232         unsigned brightness, new_brightness;
 233
 234         r = safe_atou(*value, &brightness);
 235         if (r < 0) {
 236                 log_warning("Failed to parse brightness \"%s\": %s", *value, strerror(-r));
 237                 return;
 238         }
 239
 240         new_brightness = MAX3(brightness, 1U, max_brightness/20);
 241         if (new_brightness != brightness) {
 242                 char *old_value = *value;
 243
 244                 r = asprintf(value, "%u", new_brightness);
 245                 if (r < 0) {
 246                         log_oom();
 247                         return;
 248                 }
 249
 250                 log_debug("Saved brightness %s too low; increasing to %s.", old_value, *value);
 251                 free(old_value);
 252         }
 253 }
 254
 255 int main(int argc, char *argv[]) {
 256         _cleanup_udev_unref_ struct udev *udev = NULL;
 257         _cleanup_udev_device_unref_ struct udev_device *device = NULL;
 258         _cleanup_free_ char *saved = NULL, *ss = NULL, *escaped_ss = NULL, *escaped_sysname = NULL, *escaped_path_id = NULL;
 259         const char *sysname, *path_id;
 260         unsigned max_brightness;
 261         int r;
 262
 263         if (argc != 3) {
 264                 log_error("This program requires two arguments.");
 265                 return EXIT_FAILURE;
 266         }
 267
 268         log_set_target(LOG_TARGET_AUTO);
 269         log_parse_environment();
 270         log_open();
 271
 272         umask(0022);
 273
 274         r = mkdir_p("/var/lib/systemd/backlight", 0755);
 275         if (r < 0) {
 276                 log_error("Failed to create backlight directory /var/lib/systemd/backlight: %s",
 277                           strerror(-r));
 278                 return EXIT_FAILURE;
 279         }
 280
 281         udev = udev_new();
 282         if (!udev) {
 283                 log_oom();
 284                 return EXIT_FAILURE;
 285         }
 286
 287         sysname = strchr(argv[2], ':');
 288         if (!sysname) {
 289                 log_error("Requires a subsystem and sysname pair specifying a backlight device.");
 290                 return EXIT_FAILURE;
 291         }
 292
 293         ss = strndup(argv[2], sysname - argv[2]);
 294         if (!ss) {
 295                 log_oom();
 296                 return EXIT_FAILURE;
 297         }
 298
 299         sysname++;
 300
 301         if (!streq(ss, "backlight") && !streq(ss, "leds")) {
 302                 log_error("Not a backlight or LED device: '%s:%s'", ss, sysname);
 303                 return EXIT_FAILURE;
 304         }
 305
 306         errno = 0;
 307         device = udev_device_new_from_subsystem_sysname(udev, ss, sysname);
 308         if (!device) {
 309                 if (errno != 0)
 310                         log_error("Failed to get backlight or LED device '%s:%s': %m", ss, sysname);
 311                 else
 312                         log_oom();
 313
 314                 return EXIT_FAILURE;
 315         }
 316
 317         /* If max_brightness is 0, then there is no actual backlight
 318          * device. This happens on desktops with Asus mainboards
 319          * that load the eeepc-wmi module.
 320          */
 321         max_brightness = get_max_brightness(device);
 322         if (max_brightness == 0)
 323                 return EXIT_SUCCESS;
 324
 325         escaped_ss = cescape(ss);
 326         if (!escaped_ss) {
 327                 log_oom();
 328                 return EXIT_FAILURE;
 329         }
 330
 331         escaped_sysname = cescape(sysname);
 332         if (!escaped_sysname) {
 333                 log_oom();
 334                 return EXIT_FAILURE;
 335         }
 336
 337         path_id = udev_device_get_property_value(device, "ID_PATH");
 338         if (path_id) {
 339                 escaped_path_id = cescape(path_id);
 340                 if (!escaped_path_id) {
 341                         log_oom();
 342                         return EXIT_FAILURE;
 343                 }
 344
 345                 saved = strjoin("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_ss, ":", escaped_sysname, NULL);
 346         } else
 347                 saved = strjoin("/var/lib/systemd/backlight/", escaped_ss, ":", escaped_sysname, NULL);
 348
 349         if (!saved) {
 350                 log_oom();
 351                 return EXIT_FAILURE;
 352         }
 353
 354         /* If there are multiple conflicting backlight devices, then
 355          * their probing at boot-time might happen in any order. This
 356          * means the validity checking of the device then is not
 357          * reliable, since it might not see other devices conflicting
 358          * with a specific backlight. To deal with this, we will
 359          * actively delete backlight state files at shutdown (where
 360          * device probing should be complete), so that the validity
 361          * check at boot time doesn't have to be reliable. */
 362
 363         if (streq(argv[1], "load") && shall_restore_state()) {
 364                 _cleanup_free_ char *value = NULL;
 365
 366                 if (!validate_device(udev, device))
 367                         return EXIT_SUCCESS;
 368
 369                 r = read_one_line_file(saved, &value);
 370                 if (r < 0) {
 371
 372                         if (r == -ENOENT)
 373                                 return EXIT_SUCCESS;
 374
 375                         log_error("Failed to read %s: %s", saved, strerror(-r));
 376                         return EXIT_FAILURE;
 377                 }
 378
 379                 clamp_brightness(device, &value, max_brightness);
 380
 381                 r = udev_device_set_sysattr_value(device, "brightness", value);
 382                 if (r < 0) {
 383                         log_error("Failed to write system 'brightness' attribute: %s",
 384                                   strerror(-r));
 385                         return EXIT_FAILURE;
 386                 }
 387
 388         } else if (streq(argv[1], "save")) {
 389                 const char *value;
 390
 391                 if (!validate_device(udev, device)) {
 392                         unlink(saved);
 393                         return EXIT_SUCCESS;
 394                 }
 395
 396                 value = udev_device_get_sysattr_value(device, "brightness");
 397                 if (!value) {
 398                         log_error("Failed to read system 'brightness' attribute");
 399                         return EXIT_FAILURE;
 400                 }
 401
 402                 r = write_string_file(saved, value);
 403                 if (r < 0) {
 404                         log_error("Failed to write %s: %s", saved, strerror(-r));
 405                         return EXIT_FAILURE;
 406                 }
 407
 408         } else {
 409                 log_error("Unknown verb %s.", argv[1]);
 410                 return EXIT_FAILURE;
 411         }
 412
 413         return EXIT_SUCCESS;
 414 }