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
  28 static struct udev_device *find_pci_or_platform_parent(struct udev_device *device) {
  29         struct udev_device *parent;
  30         const char *subsystem, *sysname;
  31
  32         assert(device);
  33
  34         parent = udev_device_get_parent(device);
  35         if (!parent)
  36                 return NULL;
  37
  38         subsystem = udev_device_get_subsystem(parent);
  39         if (!subsystem)
  40                 return NULL;
  41
  42         sysname = udev_device_get_sysname(parent);
  43         if (!sysname)
  44                 return NULL;
  45
  46         if (streq(subsystem, "drm")) {
  47                 const char *c;
  48
  49                 c = startswith(sysname, "card");
  50                 if (!c)
  51                         return NULL;
  52
  53                 c += strspn(c, "0123456789");
  54                 if (*c == '-') {
  55                         /* A connector DRM device, let's ignore all but LVDS and eDP! */
  56
  57                         if (!startswith(c, "-LVDS-") &&
  58                             !startswith(c, "-Embedded DisplayPort-"))
  59                                 return NULL;
  60                 }
  61
  62         } else if (streq(subsystem, "pci")) {
  63                 const char *value;
  64
  65                 value = udev_device_get_sysattr_value(parent, "class");
  66                 if (value) {
  67                         unsigned long class = 0;
  68
  69                         if (safe_atolu(value, &class) < 0) {
  70                                 log_warning("Cannot parse PCI class %s of device %s:%s.", value, subsystem, sysname);
  71                                 return NULL;
  72                         }
  73
  74                         /* Graphics card */
  75                         if (class == 0x30000)
  76                                 return parent;
  77                 }
  78
  79         } else if (streq(subsystem, "platform"))
  80                 return parent;
  81
  82         return find_pci_or_platform_parent(parent);
  83 }
  84
  85 static bool same_device(struct udev_device *a, struct udev_device *b) {
  86         assert(a);
  87         assert(b);
  88
  89         if (!streq_ptr(udev_device_get_subsystem(a), udev_device_get_subsystem(b)))
  90                 return false;
  91
  92         if (!streq_ptr(udev_device_get_sysname(a), udev_device_get_sysname(b)))
  93                 return false;
  94
  95         return true;
  96 }
  97
  98 static bool validate_device(struct udev *udev, struct udev_device *device) {
  99         _cleanup_udev_enumerate_unref_ struct udev_enumerate *enumerate = NULL;
 100         struct udev_list_entry *item = NULL, *first = NULL;
 101         struct udev_device *parent;
 102         const char *v, *subsystem;
 103         int r;
 104
 105         assert(udev);
 106         assert(device);
 107
 108         /* Verify whether we should actually care for a specific
 109          * backlight device. For backlight devices there might be
 110          * multiple ways to access the same control: "firmware"
 111          * (i.e. ACPI), "platform" (i.e. via the machine's EC) and
 112          * "raw" (via the graphics card). In general we should prefer
 113          * "firmware" (i.e. ACPI) or "platform" access over "raw"
 114          * access, in order not to confuse the BIOS/EC, and
 115          * compatibility with possible low-level hotkey handling of
 116          * screen brightness. The kernel will already make sure to
 117          * expose only one of "firmware" and "platform" for the same
 118          * device to userspace. However, we still need to make sure
 119          * that we use "raw" only if no "firmware" or "platform"
 120          * device for the same device exists. */
 121
 122         subsystem = udev_device_get_subsystem(device);
 123         if (!streq_ptr(subsystem, "backlight"))
 124                 return true;
 125
 126         v = udev_device_get_sysattr_value(device, "type");
 127         if (!streq_ptr(v, "raw"))
 128                 return true;
 129
 130         parent = find_pci_or_platform_parent(device);
 131         if (!parent)
 132                 return true;
 133
 134         subsystem = udev_device_get_subsystem(parent);
 135         if (!subsystem)
 136                 return true;
 137
 138         enumerate = udev_enumerate_new(udev);
 139         if (!enumerate)
 140                 return true;
 141
 142         r = udev_enumerate_add_match_subsystem(enumerate, "backlight");
 143         if (r < 0)
 144                 return true;
 145
 146         r = udev_enumerate_scan_devices(enumerate);
 147         if (r < 0)
 148                 return true;
 149
 150         first = udev_enumerate_get_list_entry(enumerate);
 151         udev_list_entry_foreach(item, first) {
 152                 _cleanup_udev_device_unref_ struct udev_device *other;
 153                 struct udev_device *other_parent;
 154                 const char *other_subsystem;
 155
 156                 other = udev_device_new_from_syspath(udev, udev_list_entry_get_name(item));
 157                 if (!other)
 158                         return true;
 159
 160                 if (same_device(device, other))
 161                         continue;
 162
 163                 v = udev_device_get_sysattr_value(other, "type");
 164                 if (!streq_ptr(v, "platform") && !streq_ptr(v, "firmware"))
 165                         continue;
 166
 167                 /* OK, so there's another backlight device, and it's a
 168                  * platform or firmware device, so, let's see if we
 169                  * can verify it belongs to the same device as
 170                  * ours. */
 171                 other_parent = find_pci_or_platform_parent(other);
 172                 if (!other_parent)
 173                         continue;
 174
 175                 if (same_device(parent, other_parent)) {
 176                         /* Both have the same PCI parent, that means
 177                          * we are out. */
 178                         log_debug("Skipping backlight device %s, since backlight device %s is on same PCI device and, takes precedence.", udev_device_get_sysname(device), udev_device_get_sysname(other));
 179                         return false;
 180                 }
 181
 182                 other_subsystem = udev_device_get_subsystem(other_parent);
 183                 if (streq_ptr(other_subsystem, "platform") && streq_ptr(subsystem, "pci")) {
 184                         /* The other is connected to the platform bus
 185                          * and we are a PCI device, that also means we
 186                          * are out. */
 187                         log_debug("Skipping backlight device %s, since backlight device %s is a platform device and takes precedence.", udev_device_get_sysname(device), udev_device_get_sysname(other));
 188                         return false;
 189                 }
 190         }
 191
 192         return true;
 193 }
 194
 195 int main(int argc, char *argv[]) {
 196         _cleanup_udev_unref_ struct udev *udev = NULL;
 197         _cleanup_udev_device_unref_ struct udev_device *device = NULL;
 198         _cleanup_free_ char *saved = NULL, *ss = NULL, *escaped_ss = NULL, *escaped_sysname = NULL, *escaped_path_id = NULL;
 199         const char *sysname, *path_id;
 200         int r;
 201
 202         if (argc != 3) {
 203                 log_error("This program requires two arguments.");
 204                 return EXIT_FAILURE;
 205         }
 206
 207         log_set_target(LOG_TARGET_AUTO);
 208         log_parse_environment();
 209         log_open();
 210
 211         umask(0022);
 212
 213         r = mkdir_p("/var/lib/systemd/backlight", 0755);
 214         if (r < 0) {
 215                 log_error("Failed to create backlight directory: %s", strerror(-r));
 216                 return EXIT_FAILURE;
 217         }
 218
 219         udev = udev_new();
 220         if (!udev) {
 221                 log_oom();
 222                 return EXIT_FAILURE;
 223         }
 224
 225         sysname = strchr(argv[2], ':');
 226         if (!sysname) {
 227                 log_error("Requires pair of subsystem and sysname for specifying backlight device.");
 228                 return EXIT_FAILURE;
 229         }
 230
 231         ss = strndup(argv[2], sysname - argv[2]);
 232         if (!ss) {
 233                 log_oom();
 234                 return EXIT_FAILURE;
 235         }
 236
 237         sysname++;
 238
 239         if (!streq(ss, "backlight") && !streq(ss, "leds")) {
 240                 log_error("Not a backlight or LED device: '%s:%s'", ss, sysname);
 241                 return EXIT_FAILURE;
 242         }
 243
 244         errno = 0;
 245         device = udev_device_new_from_subsystem_sysname(udev, ss, sysname);
 246         if (!device) {
 247                 if (errno != 0)
 248                         log_error("Failed to get backlight or LED device '%s:%s': %m", ss, sysname);
 249                 else
 250                         log_oom();
 251
 252                 return EXIT_FAILURE;
 253         }
 254
 255         escaped_ss = cescape(ss);
 256         if (!escaped_ss) {
 257                 log_oom();
 258                 return EXIT_FAILURE;
 259         }
 260
 261         escaped_sysname = cescape(sysname);
 262         if (!escaped_sysname) {
 263                 log_oom();
 264                 return EXIT_FAILURE;
 265         }
 266
 267         path_id = udev_device_get_property_value(device, "ID_PATH");
 268         if (path_id) {
 269                 escaped_path_id = cescape(path_id);
 270                 if (!escaped_path_id) {
 271                         log_oom();
 272                         return EXIT_FAILURE;
 273                 }
 274
 275                 saved = strjoin("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_ss, ":", escaped_sysname, NULL);
 276         } else
 277                 saved = strjoin("/var/lib/systemd/backlight/", escaped_ss, ":", escaped_sysname, NULL);
 278
 279         if (!saved) {
 280                 log_oom();
 281                 return EXIT_FAILURE;
 282         }
 283
 284         /* If there are multiple conflicting backlight devices, then
 285          * their probing at boot-time might happen in any order. This
 286          * means the validity checking of the device then is not
 287          * reliable, since it might not see other devices conflicting
 288          * with a specific backlight. To deal with this, we will
 289          * actively delete backlight state files at shutdown (where
 290          * device probing should be complete), so that the validity
 291          * check at boot time doesn't have to be reliable. */
 292
 293         if (streq(argv[1], "load") && shall_restore_state()) {
 294                 _cleanup_free_ char *value = NULL;
 295
 296                 if (!validate_device(udev, device))
 297                         return EXIT_SUCCESS;
 298
 299                 r = read_one_line_file(saved, &value);
 300                 if (r < 0) {
 301
 302                         if (r == -ENOENT)
 303                                 return EXIT_SUCCESS;
 304
 305                         log_error("Failed to read %s: %s", saved, strerror(-r));
 306                         return EXIT_FAILURE;
 307                 }
 308
 309                 r = udev_device_set_sysattr_value(device, "brightness", value);
 310                 if (r < 0) {
 311                         log_error("Failed to write system attribute: %s", strerror(-r));
 312                         return EXIT_FAILURE;
 313                 }
 314
 315         } else if (streq(argv[1], "save")) {
 316                 const char *value;
 317
 318                 if (!validate_device(udev, device)) {
 319                         unlink(saved);
 320                         return EXIT_SUCCESS;
 321                 }
 322
 323                 value = udev_device_get_sysattr_value(device, "brightness");
 324                 if (!value) {
 325                         log_error("Failed to read system attribute");
 326                         return EXIT_FAILURE;
 327                 }
 328
 329                 r = write_string_file(saved, value);
 330                 if (r < 0) {
 331                         log_error("Failed to write %s: %s", saved, strerror(-r));
 332                         return EXIT_FAILURE;
 333                 }
 334
 335         } else {
 336                 log_error("Unknown verb %s.", argv[1]);
 337                 return EXIT_FAILURE;
 338         }
 339
 340         return EXIT_SUCCESS;
 341 }