src/backlight/backlight.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include "sd-device.h"
   4
   5 #include "alloc-util.h"
   6 #include "def.h"
   7 #include "device-util.h"
   8 #include "escape.h"
   9 #include "fileio.h"
  10 #include "mkdir.h"
  11 #include "parse-util.h"
  12 #include "proc-cmdline.h"
  13 #include "string-util.h"
  14 #include "strv.h"
  15 #include "util.h"
  16
  17 static int find_pci_or_platform_parent(sd_device *device, sd_device **ret) {
  18         const char *subsystem, *sysname, *value;
  19         sd_device *parent;
  20         int r;
  21
  22         assert(device);
  23         assert(ret);
  24
  25         r = sd_device_get_parent(device, &parent);
  26         if (r < 0)
  27                 return r;
  28
  29         r = sd_device_get_subsystem(parent, &subsystem);
  30         if (r < 0)
  31                 return r;
  32
  33         r = sd_device_get_sysname(parent, &sysname);
  34         if (r < 0)
  35                 return r;
  36
  37         if (streq(subsystem, "drm")) {
  38                 const char *c;
  39
  40                 c = startswith(sysname, "card");
  41                 if (!c)
  42                         return -ENODATA;
  43
  44                 c += strspn(c, DIGITS);
  45                 if (*c == '-') {
  46                         /* A connector DRM device, let's ignore all but LVDS and eDP! */
  47
  48                         if (!startswith(c, "-LVDS-") &&
  49                             !startswith(c, "-Embedded DisplayPort-"))
  50                                 return -EOPNOTSUPP;
  51                 }
  52
  53         } else if (streq(subsystem, "pci") &&
  54                    sd_device_get_sysattr_value(parent, "class", &value) >= 0) {
  55                 unsigned long class = 0;
  56
  57                 r = safe_atolu(value, &class);
  58                 if (r < 0)
  59                         return log_warning_errno(r, "Cannot parse PCI class '%s' of device %s:%s: %m",
  60                                                  value, subsystem, sysname);
  61
  62                 /* Graphics card */
  63                 if (class == 0x30000) {
  64                         *ret = parent;
  65                         return 0;
  66                 }
  67
  68         } else if (streq(subsystem, "platform")) {
  69                 *ret = parent;
  70                 return 0;
  71         }
  72
  73         return find_pci_or_platform_parent(parent, ret);
  74 }
  75
  76 static int same_device(sd_device *a, sd_device *b) {
  77         const char *a_val, *b_val;
  78         int r;
  79
  80         assert(a);
  81         assert(b);
  82
  83         r = sd_device_get_subsystem(a, &a_val);
  84         if (r < 0)
  85                 return r;
  86
  87         r = sd_device_get_subsystem(b, &b_val);
  88         if (r < 0)
  89                 return r;
  90
  91         if (!streq(a_val, b_val))
  92                 return false;
  93
  94         r = sd_device_get_sysname(a, &a_val);
  95         if (r < 0)
  96                 return r;
  97
  98         r = sd_device_get_sysname(b, &b_val);
  99         if (r < 0)
 100                 return r;
 101
 102         return streq(a_val, b_val);
 103 }
 104
 105 static int validate_device(sd_device *device) {
 106         _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *enumerate = NULL;
 107         const char *v, *subsystem;
 108         sd_device *parent, *other;
 109         int r;
 110
 111         assert(device);
 112
 113         /* Verify whether we should actually care for a specific
 114          * backlight device. For backlight devices there might be
 115          * multiple ways to access the same control: "firmware"
 116          * (i.e. ACPI), "platform" (i.e. via the machine's EC) and
 117          * "raw" (via the graphics card). In general we should prefer
 118          * "firmware" (i.e. ACPI) or "platform" access over "raw"
 119          * access, in order not to confuse the BIOS/EC, and
 120          * compatibility with possible low-level hotkey handling of
 121          * screen brightness. The kernel will already make sure to
 122          * expose only one of "firmware" and "platform" for the same
 123          * device to userspace. However, we still need to make sure
 124          * that we use "raw" only if no "firmware" or "platform"
 125          * device for the same device exists. */
 126
 127         r = sd_device_get_subsystem(device, &subsystem);
 128         if (r < 0)
 129                 return r;
 130         if (!streq(subsystem, "backlight"))
 131                 return true;
 132
 133         r = sd_device_get_sysattr_value(device, "type", &v);
 134         if (r < 0)
 135                 return r;
 136         if (!streq(v, "raw"))
 137                 return true;
 138
 139         r = find_pci_or_platform_parent(device, &parent);
 140         if (r < 0)
 141                 return r;
 142
 143         r = sd_device_get_subsystem(parent, &subsystem);
 144         if (r < 0)
 145                 return r;
 146
 147         r = sd_device_enumerator_new(&enumerate);
 148         if (r < 0)
 149                 return r;
 150
 151         r = sd_device_enumerator_allow_uninitialized(enumerate);
 152         if (r < 0)
 153                 return r;
 154
 155         r = sd_device_enumerator_add_match_subsystem(enumerate, "backlight", true);
 156         if (r < 0)
 157                 return r;
 158
 159         FOREACH_DEVICE(enumerate, other) {
 160                 const char *other_subsystem;
 161                 sd_device *other_parent;
 162
 163                 if (same_device(device, other) > 0)
 164                         continue;
 165
 166                 if (sd_device_get_sysattr_value(other, "type", &v) < 0 ||
 167                     !STR_IN_SET(v, "platform", "firmware"))
 168                         continue;
 169
 170                 /* OK, so there's another backlight device, and it's a
 171                  * platform or firmware device, so, let's see if we
 172                  * can verify it belongs to the same device as ours. */
 173                 if (find_pci_or_platform_parent(other, &other_parent) < 0)
 174                         continue;
 175
 176                 if (same_device(parent, other_parent)) {
 177                         const char *device_sysname = NULL, *other_sysname = NULL;
 178
 179                         /* Both have the same PCI parent, that means we are out. */
 180
 181                         (void) sd_device_get_sysname(device, &device_sysname);
 182                         (void) sd_device_get_sysname(other, &other_sysname);
 183
 184                         log_debug("Skipping backlight device %s, since device %s is on same PCI device and takes precedence.",
 185                                   device_sysname, other_sysname);
 186                         return false;
 187                 }
 188
 189                 if (sd_device_get_subsystem(other_parent, &other_subsystem) < 0)
 190                         continue;
 191
 192                 if (streq(other_subsystem, "platform") && streq(subsystem, "pci")) {
 193                         const char *device_sysname = NULL, *other_sysname = NULL;
 194
 195                         /* The other is connected to the platform bus and we are a PCI device, that also means we are out. */
 196
 197                         (void) sd_device_get_sysname(device, &device_sysname);
 198                         (void) sd_device_get_sysname(other, &other_sysname);
 199
 200                         log_debug("Skipping backlight device %s, since device %s is a platform device and takes precedence.",
 201                                   device_sysname, other_sysname);
 202                         return false;
 203                 }
 204         }
 205
 206         return true;
 207 }
 208
 209 static int get_max_brightness(sd_device *device, unsigned *ret) {
 210         const char *max_brightness_str;
 211         unsigned max_brightness;
 212         int r;
 213
 214         assert(device);
 215         assert(ret);
 216
 217         r = sd_device_get_sysattr_value(device, "max_brightness", &max_brightness_str);
 218         if (r < 0)
 219                 return log_warning_errno(r, "Failed to read 'max_brightness' attribute: %m");
 220
 221         r = safe_atou(max_brightness_str, &max_brightness);
 222         if (r < 0)
 223                 return log_warning_errno(r, "Failed to parse 'max_brightness' \"%s\": %m", max_brightness_str);
 224
 225         if (max_brightness <= 0) {
 226                 log_warning("Maximum brightness is 0, ignoring device.");
 227                 return -EINVAL;
 228         }
 229
 230         *ret = max_brightness;
 231         return 0;
 232 }
 233
 234 /* Some systems turn the backlight all the way off at the lowest levels.
 235  * clamp_brightness clamps the saved brightness to at least 1 or 5% of
 236  * max_brightness in case of 'backlight' subsystem. This avoids preserving
 237  * an unreadably dim screen, which would otherwise force the user to
 238  * disable state restoration. */
 239 static int clamp_brightness(sd_device *device, char **value, unsigned max_brightness) {
 240         unsigned brightness, new_brightness, min_brightness;
 241         const char *subsystem;
 242         int r;
 243
 244         assert(value);
 245         assert(*value);
 246
 247         r = safe_atou(*value, &brightness);
 248         if (r < 0)
 249                 return log_warning_errno(r, "Failed to parse brightness \"%s\": %m", *value);
 250
 251         r = sd_device_get_subsystem(device, &subsystem);
 252         if (r < 0)
 253                 return log_warning_errno(r, "Failed to get device subsystem: %m");
 254
 255         if (streq(subsystem, "backlight"))
 256                 min_brightness = MAX(1U, max_brightness/20);
 257         else
 258                 min_brightness = 0;
 259
 260         new_brightness = CLAMP(brightness, min_brightness, max_brightness);
 261         if (new_brightness != brightness) {
 262                 char *new_value;
 263
 264                 r = asprintf(&new_value, "%u", new_brightness);
 265                 if (r < 0)
 266                         return log_oom();
 267
 268                 log_info("Saved brightness %s %s to %s.", *value,
 269                          new_brightness > brightness ?
 270                          "too low; increasing" : "too high; decreasing",
 271                          new_value);
 272
 273                 free_and_replace(*value, new_value);
 274         }
 275
 276         return 0;
 277 }
 278
 279 static bool shall_clamp(sd_device *d) {
 280         const char *s;
 281         int r;
 282
 283         assert(d);
 284
 285         r = sd_device_get_property_value(d, "ID_BACKLIGHT_CLAMP", &s);
 286         if (r < 0)
 287                 return true;
 288
 289         r = parse_boolean(s);
 290         if (r < 0) {
 291                 log_debug_errno(r, "Failed to parse ID_BACKLIGHT_CLAMP property, ignoring: %m");
 292                 return true;
 293         }
 294
 295         return r;
 296 }
 297
 298 int main(int argc, char *argv[]) {
 299         _cleanup_(sd_device_unrefp) sd_device *device = NULL;
 300         _cleanup_free_ char *escaped_ss = NULL, *escaped_sysname = NULL, *escaped_path_id = NULL;
 301         const char *sysname, *path_id, *ss, *saved;
 302         unsigned max_brightness;
 303         int r;
 304
 305         if (argc != 3) {
 306                 log_error("This program requires two arguments.");
 307                 return EXIT_FAILURE;
 308         }
 309
 310         log_set_target(LOG_TARGET_AUTO);
 311         log_parse_environment();
 312         log_open();
 313
 314         umask(0022);
 315
 316         r = mkdir_p("/var/lib/systemd/backlight", 0755);
 317         if (r < 0) {
 318                 log_error_errno(r, "Failed to create backlight directory /var/lib/systemd/backlight: %m");
 319                 return EXIT_FAILURE;
 320         }
 321
 322         sysname = strchr(argv[2], ':');
 323         if (!sysname) {
 324                 log_error("Requires a subsystem and sysname pair specifying a backlight device.");
 325                 return EXIT_FAILURE;
 326         }
 327
 328         ss = strndupa(argv[2], sysname - argv[2]);
 329
 330         sysname++;
 331
 332         if (!STR_IN_SET(ss, "backlight", "leds")) {
 333                 log_error("Not a backlight or LED device: '%s:%s'", ss, sysname);
 334                 return EXIT_FAILURE;
 335         }
 336
 337         r = sd_device_new_from_subsystem_sysname(&device, ss, sysname);
 338         if (r < 0) {
 339                 log_error_errno(r, "Failed to get backlight or LED device '%s:%s': %m", ss, sysname);
 340                 return EXIT_FAILURE;
 341         }
 342
 343         /* If max_brightness is 0, then there is no actual backlight
 344          * device. This happens on desktops with Asus mainboards
 345          * that load the eeepc-wmi module. */
 346         r = get_max_brightness(device, &max_brightness);
 347         if (r < 0)
 348                 return EXIT_SUCCESS;
 349
 350         escaped_ss = cescape(ss);
 351         if (!escaped_ss) {
 352                 log_oom();
 353                 return EXIT_FAILURE;
 354         }
 355
 356         escaped_sysname = cescape(sysname);
 357         if (!escaped_sysname) {
 358                 log_oom();
 359                 return EXIT_FAILURE;
 360         }
 361
 362         if (sd_device_get_property_value(device, "ID_PATH", &path_id) >= 0) {
 363                 escaped_path_id = cescape(path_id);
 364                 if (!escaped_path_id) {
 365                         log_oom();
 366                         return EXIT_FAILURE;
 367                 }
 368
 369                 saved = strjoina("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_ss, ":", escaped_sysname);
 370         } else
 371                 saved = strjoina("/var/lib/systemd/backlight/", escaped_ss, ":", escaped_sysname);
 372
 373         /* If there are multiple conflicting backlight devices, then
 374          * their probing at boot-time might happen in any order. This
 375          * means the validity checking of the device then is not
 376          * reliable, since it might not see other devices conflicting
 377          * with a specific backlight. To deal with this, we will
 378          * actively delete backlight state files at shutdown (where
 379          * device probing should be complete), so that the validity
 380          * check at boot time doesn't have to be reliable. */
 381
 382         if (streq(argv[1], "load")) {
 383                 _cleanup_free_ char *value = NULL;
 384                 bool clamp;
 385
 386                 if (shall_restore_state() == 0)
 387                         return EXIT_SUCCESS;
 388
 389                 if (validate_device(device) == 0)
 390                         return EXIT_SUCCESS;
 391
 392                 clamp = shall_clamp(device);
 393
 394                 r = read_one_line_file(saved, &value);
 395                 if (r == -ENOENT) {
 396                         const char *curval;
 397
 398                         /* Fallback to clamping current brightness or exit early if
 399                          * clamping is not supported/enabled. */
 400                         if (!clamp)
 401                                 return EXIT_SUCCESS;
 402
 403                         r = sd_device_get_sysattr_value(device, "brightness", &curval);
 404                         if (r < 0) {
 405                                 log_warning_errno(r, "Failed to read 'brightness' attribute: %m");
 406                                 return EXIT_FAILURE;
 407                         }
 408
 409                         value = strdup(curval);
 410                         if (!value) {
 411                                 log_oom();
 412                                 return EXIT_FAILURE;
 413                         }
 414                 } else if (r < 0) {
 415                         log_error_errno(r, "Failed to read %s: %m", saved);
 416                         return EXIT_FAILURE;
 417                 }
 418
 419                 if (clamp)
 420                         (void) clamp_brightness(device, &value, max_brightness);
 421
 422                 r = sd_device_set_sysattr_value(device, "brightness", value);
 423                 if (r < 0) {
 424                         log_error_errno(r, "Failed to write system 'brightness' attribute: %m");
 425                         return EXIT_FAILURE;
 426                 }
 427
 428         } else if (streq(argv[1], "save")) {
 429                 const char *value;
 430
 431                 if (validate_device(device) == 0) {
 432                         unlink(saved);
 433                         return EXIT_SUCCESS;
 434                 }
 435
 436                 r = sd_device_get_sysattr_value(device, "brightness", &value);
 437                 if (r < 0) {
 438                         log_error_errno(r, "Failed to read system 'brightness' attribute: %m");
 439                         return EXIT_FAILURE;
 440                 }
 441
 442                 r = write_string_file(saved, value, WRITE_STRING_FILE_CREATE);
 443                 if (r < 0) {
 444                         log_error_errno(r, "Failed to write %s: %m", saved);
 445                         return EXIT_FAILURE;
 446                 }
 447
 448         } else {
 449                 log_error("Unknown verb %s.", argv[1]);
 450                 return EXIT_FAILURE;
 451         }
 452
 453         return EXIT_SUCCESS;
 454 }