src/backlight/backlight.c

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