udev_sysfs.c

   1 /*
   2  * Copyright (C) 2005-2006 Kay Sievers <kay.sievers@vrfy.org>
   3  *
   4  *      This program is free software; you can redistribute it and/or modify it
   5  *      under the terms of the GNU General Public License as published by the
   6  *      Free Software Foundation version 2 of the License.
   7  *
   8  *      This program is distributed in the hope that it will be useful, but
   9  *      WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  *      General Public License for more details.
  12  *
  13  *      You should have received a copy of the GNU General Public License along
  14  *      with this program; if not, write to the Free Software Foundation, Inc.,
  15  *      51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  16  *
  17  */
  18
  19
  20 #include <stdlib.h>
  21 #include <stdio.h>
  22 #include <stddef.h>
  23 #include <unistd.h>
  24 #include <fcntl.h>
  25 #include <ctype.h>
  26 #include <errno.h>
  27 #include <sys/stat.h>
  28
  29 #include "udev.h"
  30
  31 char sysfs_path[PATH_SIZE];
  32
  33 /* device cache */
  34 static LIST_HEAD(dev_list);
  35
  36 /* attribute value cache */
  37 static LIST_HEAD(attr_list);
  38 struct sysfs_attr {
  39         struct list_head node;
  40         char path[PATH_SIZE];
  41         char *value;                    /* points to value_local if value is cached */
  42         char value_local[NAME_SIZE];
  43 };
  44
  45 int sysfs_init(void)
  46 {
  47         const char *env;
  48
  49         env = getenv("SYSFS_PATH");
  50         if (env) {
  51                 strlcpy(sysfs_path, env, sizeof(sysfs_path));
  52                 remove_trailing_chars(sysfs_path, '/');
  53         } else
  54                 strlcpy(sysfs_path, "/sys", sizeof(sysfs_path));
  55         dbg("sysfs_path='%s'", sysfs_path);
  56
  57         INIT_LIST_HEAD(&dev_list);
  58         INIT_LIST_HEAD(&attr_list);
  59         return 0;
  60 }
  61
  62 void sysfs_cleanup(void)
  63 {
  64         struct sysfs_attr *attr_loop;
  65         struct sysfs_attr *attr_temp;
  66         struct sysfs_device *dev_loop;
  67         struct sysfs_device *dev_temp;
  68
  69         list_for_each_entry_safe(attr_loop, attr_temp, &attr_list, node) {
  70                 list_del(&attr_loop->node);
  71                 free(attr_loop);
  72         }
  73
  74         list_for_each_entry_safe(dev_loop, dev_temp, &dev_list, node) {
  75                 list_del(&dev_loop->node);
  76                 free(dev_loop);
  77         }
  78 }
  79
  80 void sysfs_device_set_values(struct sysfs_device *dev, const char *devpath,
  81                              const char *subsystem, const char *driver)
  82 {
  83         char *pos;
  84
  85         strlcpy(dev->devpath, devpath, sizeof(dev->devpath));
  86         if (subsystem != NULL)
  87                 strlcpy(dev->subsystem, subsystem, sizeof(dev->subsystem));
  88         if (driver != NULL)
  89                 strlcpy(dev->driver, driver, sizeof(dev->driver));
  90
  91         /* set kernel name */
  92         pos = strrchr(dev->devpath, '/');
  93         if (pos == NULL)
  94                 return;
  95
  96         strlcpy(dev->kernel, &pos[1], sizeof(dev->kernel));
  97         dbg("kernel='%s'", dev->kernel);
  98
  99         /* some devices have '!' in their name, change that to '/' */
 100         pos = dev->kernel;
 101         while (pos[0] != '\0') {
 102                 if (pos[0] == '!')
 103                         pos[0] = '/';
 104                 pos++;
 105         }
 106
 107         /* get kernel number */
 108         pos = &dev->kernel[strlen(dev->kernel)];
 109         while (isdigit(pos[-1]))
 110                 pos--;
 111         strlcpy(dev->kernel_number, pos, sizeof(dev->kernel_number));
 112         dbg("kernel_number='%s'", dev->kernel_number);
 113 }
 114
 115 struct sysfs_device *sysfs_device_get(const char *devpath)
 116 {
 117         char path[PATH_SIZE];
 118         char devpath_real[PATH_SIZE];
 119         struct sysfs_device *dev;
 120         struct sysfs_device *dev_loop;
 121         struct stat statbuf;
 122         char link_path[PATH_SIZE];
 123         char link_target[PATH_SIZE];
 124         int len;
 125         char *pos;
 126
 127         dbg("open '%s'", devpath);
 128         strlcpy(devpath_real, devpath, sizeof(devpath_real));
 129         remove_trailing_chars(devpath_real, '/');
 130
 131         /* look for device already in cache (we never put an untranslated path in the cache) */
 132         list_for_each_entry(dev_loop, &dev_list, node) {
 133                 if (strcmp(dev_loop->devpath, devpath_real) == 0) {
 134                         dbg("found in cache '%s'", dev_loop->devpath);
 135                         return dev_loop;
 136                 }
 137         }
 138
 139         /* if we got a link, resolve it to the real device */
 140         strlcpy(path, sysfs_path, sizeof(path));
 141         strlcat(path, devpath_real, sizeof(path));
 142         if (lstat(path, &statbuf) != 0) {
 143                 dbg("stat '%s' failed: %s", path, strerror(errno));
 144                 return NULL;
 145         }
 146         if (S_ISLNK(statbuf.st_mode)) {
 147                 int i;
 148                 int back;
 149
 150                 len = readlink(path, link_target, sizeof(link_target));
 151                 if (len <= 0)
 152                         return NULL;
 153                 link_target[len] = '\0';
 154                 dbg("devpath link '%s' points to '%s'", path, link_target);
 155
 156                 for (back = 0; strncmp(&link_target[back * 3], "../", 3) == 0; back++)
 157                         ;
 158                 dbg("base '%s', tail '%s', back %i", devpath_real, &link_target[back * 3], back);
 159                 for (i = 0; i <= back; i++) {
 160                         pos = strrchr(devpath_real, '/');
 161                         if (pos == NULL)
 162                                 return NULL;
 163                         pos[0] = '\0';
 164                 }
 165                 dbg("after moving back '%s'", devpath_real);
 166                 strlcat(devpath_real, "/", sizeof(devpath_real));
 167                 strlcat(devpath_real, &link_target[back * 3], sizeof(devpath_real));
 168
 169                 /* now look for device in cache after path translation */
 170                 list_for_each_entry(dev_loop, &dev_list, node) {
 171                         if (strcmp(dev_loop->devpath, devpath_real) == 0) {
 172                                 dbg("found in cache '%s'", dev_loop->devpath);
 173                                 return dev_loop;
 174                         }
 175                 }
 176         }
 177
 178         /* it is a new device */
 179         dbg("new uncached device '%s'", devpath_real);
 180         dev = malloc(sizeof(struct sysfs_device));
 181         if (dev == NULL)
 182                 return NULL;
 183         memset(dev, 0x00, sizeof(struct sysfs_device));
 184
 185         sysfs_device_set_values(dev, devpath_real, NULL, NULL);
 186
 187         /* get subsystem */
 188         if (strncmp(dev->devpath, "/class/", 7) == 0) {
 189                 strlcpy(dev->subsystem, &dev->devpath[7], sizeof(dev->subsystem));
 190                 pos = strchr(dev->subsystem, '/');
 191                 if (pos != NULL)
 192                         pos[0] = '\0';
 193                 else
 194                         dev->subsystem[0] = '\0';
 195         } else if (strncmp(dev->devpath, "/block/", 7) == 0) {
 196                 strlcpy(dev->subsystem, "block", sizeof(dev->subsystem));
 197         } else if (strncmp(dev->devpath, "/devices/", 9) == 0) {
 198                 /* get subsystem from "bus" link */
 199                 strlcpy(link_path, sysfs_path, sizeof(link_path));
 200                 strlcat(link_path, dev->devpath, sizeof(link_path));
 201                 strlcat(link_path, "/bus", sizeof(link_path));
 202                 len = readlink(link_path, link_target, sizeof(link_target));
 203                 if (len > 0) {
 204                         link_target[len] = '\0';
 205                         dbg("bus link '%s' points to '%s'", link_path, link_target);
 206                         pos = strrchr(link_target, '/');
 207                         if (pos != NULL)
 208                                 strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
 209                 } else {
 210                         /* get subsystem from "subsystem" link */
 211                         strlcpy(link_path, sysfs_path, sizeof(link_path));
 212                         strlcat(link_path, dev->devpath, sizeof(link_path));
 213                         strlcat(link_path, "/subsystem", sizeof(link_path));
 214                         len = readlink(link_path, link_target, sizeof(link_target));
 215                         if (len > 0) {
 216                                 link_target[len] = '\0';
 217                                 dbg("subsystem link '%s' points to '%s'", link_path, link_target);
 218                                 pos = strrchr(link_target, '/');
 219                                 if (pos != NULL)
 220                                         strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
 221                         }
 222                 }
 223                 /* get driver name */
 224                 strlcpy(link_path, sysfs_path, sizeof(link_path));
 225                 strlcat(link_path, dev->devpath, sizeof(link_path));
 226                 strlcat(link_path, "/driver", sizeof(link_path));
 227                 len = readlink(link_path, link_target, sizeof(link_target));
 228                 if (len > 0) {
 229                         link_target[len] = '\0';
 230                         dbg("driver link '%s' points to '%s'", link_path, link_target);
 231                         pos = strrchr(link_target, '/');
 232                         if (pos != NULL)
 233                                 strlcpy(dev->driver, &pos[1], sizeof(dev->driver));
 234                 }
 235         } else if (strncmp(dev->devpath, "/bus/", 5) == 0 && strstr(dev->devpath, "/drivers/")) {
 236                 strlcpy(dev->subsystem, "drivers", sizeof(dev->subsystem));
 237         } else if (strncmp(dev->devpath, "/module/", 8) == 0) {
 238                 strlcpy(dev->subsystem, "module", sizeof(dev->subsystem));
 239         }
 240
 241         dbg("add to cache 'devpath=%s', subsystem='%s', driver='%s'", dev->devpath, dev->subsystem, dev->driver);
 242         list_add(&dev->node, &dev_list);
 243
 244         return dev;
 245 }
 246
 247 struct sysfs_device *sysfs_device_get_parent(struct sysfs_device *dev)
 248 {
 249         char parent_devpath[PATH_SIZE];
 250         char device_link[PATH_SIZE];
 251         char device_link_target[PATH_SIZE];
 252         char *pos;
 253         int i;
 254         int len;
 255         int back;
 256
 257         dbg("open '%s'", dev->devpath);
 258
 259         /* look if we already know the parent */
 260         if (dev->parent != NULL)
 261                 return dev->parent;
 262
 263         /* requesting a parent is only valid for devices */
 264         if ((strncmp(dev->devpath, "/devices/", 9) != 0) &&
 265             (strncmp(dev->devpath, "/class/", 7) != 0) &&
 266             (strncmp(dev->devpath, "/block/", 7) != 0))
 267                 return NULL;
 268
 269         strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
 270         dbg("'%s'", parent_devpath);
 271
 272         /* strip last element */
 273         pos = strrchr(parent_devpath, '/');
 274         if (pos == NULL || pos == parent_devpath)
 275                 return NULL;
 276         pos[0] = '\0';
 277
 278         /* are we at the top level of /devices */
 279         if (strcmp(parent_devpath, "/devices") == 0) {
 280                 dbg("/devices top level");
 281                 return NULL;
 282         }
 283
 284         /* at the top level of class/block we want to follow the "device" link */
 285         if (strcmp(parent_devpath, "/block") == 0) {
 286                 dbg("/block top level, look for device link");
 287                 goto device_link;
 288         }
 289         if (strncmp(parent_devpath, "/class", 6) == 0) {
 290                 pos = strrchr(parent_devpath, '/');
 291                 if (pos == &parent_devpath[6] || pos == parent_devpath) {
 292                         dbg("/class top level, look for device link");
 293                         goto device_link;
 294                 }
 295         }
 296         /* get parent and remember it */
 297         dev->parent = sysfs_device_get(parent_devpath);
 298         return dev->parent;
 299
 300 device_link:
 301         strlcpy(device_link, sysfs_path, sizeof(device_link));
 302         strlcat(device_link, dev->devpath, sizeof(device_link));
 303         strlcat(device_link, "/device", sizeof(device_link));
 304         len = readlink(device_link, device_link_target, sizeof(device_link_target));
 305         if (len < 0)
 306                 return NULL;
 307         device_link_target[len] = '\0';
 308         dbg("device link '%s' points to '%s'", device_link, device_link_target);
 309
 310         for (back = 0; strncmp(&device_link_target[back * 3], "../", 3) == 0; back++)
 311                 ;
 312         strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
 313         dbg("base='%s', tail='%s', back=%i", parent_devpath, &device_link_target[back * 3], back);
 314         for (i = 0; i < back; i++) {
 315                 pos = strrchr(parent_devpath, '/');
 316                 if (pos == NULL)
 317                         return NULL;
 318                 pos[0] = '\0';
 319         }
 320         dbg("after moving back '%s'", parent_devpath);
 321         strlcat(parent_devpath, "/", sizeof(parent_devpath));
 322         strlcat(parent_devpath, &device_link_target[back * 3], sizeof(parent_devpath));
 323
 324         /* get parent and remember it */
 325         dev->parent = sysfs_device_get(parent_devpath);
 326         return dev->parent;
 327 }
 328
 329 struct sysfs_device *sysfs_device_get_parent_with_subsystem(struct sysfs_device *dev, const char *subsystem)
 330 {
 331         struct sysfs_device *dev_parent;
 332
 333         dev_parent = sysfs_device_get_parent(dev);
 334         while (dev_parent != NULL) {
 335                 if (strcmp(dev_parent->subsystem, subsystem) == 0)
 336                         return dev_parent;
 337                 dev_parent = sysfs_device_get_parent(dev_parent);
 338         }
 339         return NULL;
 340 }
 341
 342 char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
 343 {
 344         char path_full[PATH_SIZE];
 345         const char *path;
 346         char value[NAME_SIZE];
 347         struct sysfs_attr *attr_loop;
 348         struct sysfs_attr *attr;
 349         struct stat statbuf;
 350         int fd;
 351         ssize_t size;
 352         size_t sysfs_len;
 353
 354         dbg("open '%s'/'%s'", devpath, attr_name);
 355         sysfs_len = strlcpy(path_full, sysfs_path, sizeof(path_full));
 356         path = &path_full[sysfs_len];
 357         strlcat(path_full, devpath, sizeof(path_full));
 358         strlcat(path_full, "/", sizeof(path_full));
 359         strlcat(path_full, attr_name, sizeof(path_full));
 360
 361         /* look for attribute in cache */
 362         list_for_each_entry(attr_loop, &attr_list, node) {
 363                 if (strcmp(attr_loop->path, path) == 0) {
 364                         dbg("found in cache '%s'", attr_loop->path);
 365                         return attr_loop->value;
 366                 }
 367         }
 368
 369         /* store attribute in cache (also negatives are kept in cache) */
 370         dbg("new uncached attribute '%s'", path_full);
 371         attr = malloc(sizeof(struct sysfs_attr));
 372         if (attr == NULL)
 373                 return NULL;
 374         memset(attr, 0x00, sizeof(struct sysfs_attr));
 375         strlcpy(attr->path, path, sizeof(attr->path));
 376         dbg("add to cache '%s'", path_full);
 377         list_add(&attr->node, &attr_list);
 378
 379         if (lstat(path_full, &statbuf) != 0) {
 380                 dbg("stat '%s' failed: %s", path_full, strerror(errno));
 381                 goto out;
 382         }
 383
 384         if (S_ISLNK(statbuf.st_mode)) {
 385                 /* links return the last element of the target path */
 386                 char link_target[PATH_SIZE];
 387                 int len;
 388                 const char *pos;
 389
 390                 len = readlink(path_full, link_target, sizeof(link_target));
 391                 if (len > 0) {
 392                         link_target[len] = '\0';
 393                         pos = strrchr(link_target, '/');
 394                         if (pos != NULL) {
 395                                 dbg("cache '%s' with link value '%s'", path_full, value);
 396                                 strlcpy(attr->value_local, &pos[1], sizeof(attr->value_local));
 397                                 attr->value = attr->value_local;
 398                         }
 399                 }
 400                 goto out;
 401         }
 402
 403         /* skip directories */
 404         if (S_ISDIR(statbuf.st_mode))
 405                 goto out;
 406
 407         /* skip non-readable files */
 408         if ((statbuf.st_mode & S_IRUSR) == 0)
 409                 goto out;
 410
 411         /* read attribute value */
 412         fd = open(path_full, O_RDONLY);
 413         if (fd < 0) {
 414                 dbg("attribute '%s' does not exist", path_full);
 415                 goto out;
 416         }
 417         size = read(fd, value, sizeof(value));
 418         close(fd);
 419         if (size < 0)
 420                 goto out;
 421         if (size == sizeof(value))
 422                 goto out;
 423
 424         /* got a valid value, store and return it */
 425         value[size] = '\0';
 426         remove_trailing_chars(value, '\n');
 427         dbg("cache '%s' with attribute value '%s'", path_full, value);
 428         strlcpy(attr->value_local, value, sizeof(attr->value_local));
 429         attr->value = attr->value_local;
 430
 431 out:
 432         return attr->value;
 433 }