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 in case of 'backlight' subsystem. This avoids preserving
 229  * an unreadably dim screen, which would otherwise force the user to
 230  * disable state restoration. */
 231 static void clamp_brightness(struct udev_device *device, char **value, unsigned max_brightness) {
 232         int r;
 233         unsigned brightness, new_brightness, min_brightness;
 234         const char *subsystem;
 235
 236         r = safe_atou(*value, &brightness);
 237         if (r < 0) {
 238                 log_warning("Failed to parse brightness \"%s\": %s", *value, strerror(-r));
 239                 return;
 240         }
 241
 242         subsystem = udev_device_get_subsystem(device);
 243         if (streq_ptr(subsystem, "backlight"))
 244                 min_brightness = MAX(1U, max_brightness/20);
 245         else
 246                 min_brightness = 0;
 247
 248         new_brightness = CLAMP(brightness, min_brightness, max_brightness);
 249         if (new_brightness != brightness) {
 250                 char *old_value = *value;
 251
 252                 r = asprintf(value, "%u", new_brightness);
 253                 if (r < 0) {
 254                         log_oom();
 255                         return;
 256                 }
 257
 258                 log_info("Saved brightness %s %s to %s.", old_value,
 259                          new_brightness > brightness ?
 260                          "too low; increasing" : "too high; decreasing",
 261                          *value);
 262
 263                 free(old_value);
 264         }
 265 }
 266
 267 int main(int argc, char *argv[]) {
 268         _cleanup_udev_unref_ struct udev *udev = NULL;
 269         _cleanup_udev_device_unref_ struct udev_device *device = NULL;
 270         _cleanup_free_ char *saved = NULL, *ss = NULL, *escaped_ss = NULL, *escaped_sysname = NULL, *escaped_path_id = NULL;
 271         const char *sysname, *path_id;
 272         unsigned max_brightness;
 273         int r;
 274
 275         if (argc != 3) {
 276                 log_error("This program requires two arguments.");
 277                 return EXIT_FAILURE;
 278         }
 279
 280         log_set_target(LOG_TARGET_AUTO);
 281         log_parse_environment();
 282         log_open();
 283
 284         umask(0022);
 285
 286         r = mkdir_p("/var/lib/systemd/backlight", 0755);
 287         if (r < 0) {
 288                 log_error("Failed to create backlight directory /var/lib/systemd/backlight: %s",
 289                           strerror(-r));
 290                 return EXIT_FAILURE;
 291         }
 292
 293         udev = udev_new();
 294         if (!udev) {
 295                 log_oom();
 296                 return EXIT_FAILURE;
 297         }
 298
 299         sysname = strchr(argv[2], ':');
 300         if (!sysname) {
 301                 log_error("Requires a subsystem and sysname pair specifying a backlight device.");
 302                 return EXIT_FAILURE;
 303         }
 304
 305         ss = strndup(argv[2], sysname - argv[2]);
 306         if (!ss) {
 307                 log_oom();
 308                 return EXIT_FAILURE;
 309         }
 310
 311         sysname++;
 312
 313         if (!streq(ss, "backlight") && !streq(ss, "leds")) {
 314                 log_error("Not a backlight or LED device: '%s:%s'", ss, sysname);
 315                 return EXIT_FAILURE;
 316         }
 317
 318         errno = 0;
 319         device = udev_device_new_from_subsystem_sysname(udev, ss, sysname);
 320         if (!device) {
 321                 if (errno != 0)
 322                         log_error("Failed to get backlight or LED device '%s:%s': %m", ss, sysname);
 323                 else
 324                         log_oom();
 325
 326                 return EXIT_FAILURE;
 327         }
 328
 329         /* If max_brightness is 0, then there is no actual backlight
 330          * device. This happens on desktops with Asus mainboards
 331          * that load the eeepc-wmi module.
 332          */
 333         max_brightness = get_max_brightness(device);
 334         if (max_brightness == 0)
 335                 return EXIT_SUCCESS;
 336
 337         escaped_ss = cescape(ss);
 338         if (!escaped_ss) {
 339                 log_oom();
 340                 return EXIT_FAILURE;
 341         }
 342
 343         escaped_sysname = cescape(sysname);
 344         if (!escaped_sysname) {
 345                 log_oom();
 346                 return EXIT_FAILURE;
 347         }
 348
 349         path_id = udev_device_get_property_value(device, "ID_PATH");
 350         if (path_id) {
 351                 escaped_path_id = cescape(path_id);
 352                 if (!escaped_path_id) {
 353                         log_oom();
 354                         return EXIT_FAILURE;
 355                 }
 356
 357                 saved = strjoin("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_ss, ":", escaped_sysname, NULL);
 358         } else
 359                 saved = strjoin("/var/lib/systemd/backlight/", escaped_ss, ":", escaped_sysname, NULL);
 360
 361         if (!saved) {
 362                 log_oom();
 363                 return EXIT_FAILURE;
 364         }
 365
 366         /* If there are multiple conflicting backlight devices, then
 367          * their probing at boot-time might happen in any order. This
 368          * means the validity checking of the device then is not
 369          * reliable, since it might not see other devices conflicting
 370          * with a specific backlight. To deal with this, we will
 371          * actively delete backlight state files at shutdown (where
 372          * device probing should be complete), so that the validity
 373          * check at boot time doesn't have to be reliable. */
 374
 375         if (streq(argv[1], "load")) {
 376                 _cleanup_free_ char *value = NULL;
 377
 378                 if (!shall_restore_state())
 379                         return EXIT_SUCCESS;
 380
 381                 if (!validate_device(udev, device))
 382                         return EXIT_SUCCESS;
 383
 384                 r = read_one_line_file(saved, &value);
 385                 if (r < 0) {
 386
 387                         if (r == -ENOENT)
 388                                 return EXIT_SUCCESS;
 389
 390                         log_error("Failed to read %s: %s", saved, strerror(-r));
 391                         return EXIT_FAILURE;
 392                 }
 393
 394                 clamp_brightness(device, &value, max_brightness);
 395
 396                 r = udev_device_set_sysattr_value(device, "brightness", value);
 397                 if (r < 0) {
 398                         log_error("Failed to write system 'brightness' attribute: %s",
 399                                   strerror(-r));
 400                         return EXIT_FAILURE;
 401                 }
 402
 403         } else if (streq(argv[1], "save")) {
 404                 const char *value;
 405
 406                 if (!validate_device(udev, device)) {
 407                         unlink(saved);
 408                         return EXIT_SUCCESS;
 409                 }
 410
 411                 value = udev_device_get_sysattr_value(device, "brightness");
 412                 if (!value) {
 413                         log_error("Failed to read system 'brightness' attribute");
 414                         return EXIT_FAILURE;
 415                 }
 416
 417                 r = write_string_file(saved, value);
 418                 if (r < 0) {
 419                         log_error("Failed to write %s: %s", saved, strerror(-r));
 420                         return EXIT_FAILURE;
 421                 }
 422
 423         } else {
 424                 log_error("Unknown verb %s.", argv[1]);
 425                 return EXIT_FAILURE;
 426         }
 427
 428         return EXIT_SUCCESS;
 429 }