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