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 int sysfs_resolve_link(char *devpath, size_t size)
 116 {
 117         char link_path[PATH_SIZE];
 118         char link_target[PATH_SIZE];
 119         int len;
 120         int i;
 121         int back;
 122
 123         strlcpy(link_path, sysfs_path, sizeof(link_path));
 124         strlcat(link_path, devpath, sizeof(link_path));
 125         len = readlink(link_path, link_target, sizeof(link_target));
 126         if (len <= 0)
 127                 return -1;
 128         link_target[len] = '\0';
 129         dbg("path link '%s' points to '%s'", devpath, link_target);
 130
 131         for (back = 0; strncmp(&link_target[back * 3], "../", 3) == 0; back++)
 132                 ;
 133         dbg("base '%s', tail '%s', back %i", devpath, &link_target[back * 3], back);
 134         for (i = 0; i <= back; i++) {
 135                 char *pos = strrchr(devpath, '/');
 136
 137                 if (pos == NULL)
 138                         return -1;
 139                 pos[0] = '\0';
 140         }
 141         dbg("after moving back '%s'", devpath);
 142         strlcat(devpath, "/", size);
 143         strlcat(devpath, &link_target[back * 3], size);
 144         return 0;
 145 }
 146
 147 struct sysfs_device *sysfs_device_get(const char *devpath)
 148 {
 149         char path[PATH_SIZE];
 150         char devpath_real[PATH_SIZE];
 151         struct sysfs_device *dev;
 152         struct sysfs_device *dev_loop;
 153         struct stat statbuf;
 154         char link_path[PATH_SIZE];
 155         char link_target[PATH_SIZE];
 156         int len;
 157         char *pos;
 158
 159         dbg("open '%s'", devpath);
 160         strlcpy(devpath_real, devpath, sizeof(devpath_real));
 161         remove_trailing_chars(devpath_real, '/');
 162
 163         /* look for device already in cache (we never put an untranslated path in the cache) */
 164         list_for_each_entry(dev_loop, &dev_list, node) {
 165                 if (strcmp(dev_loop->devpath, devpath_real) == 0) {
 166                         dbg("found in cache '%s'", dev_loop->devpath);
 167                         return dev_loop;
 168                 }
 169         }
 170
 171         /* if we got a link, resolve it to the real device */
 172         strlcpy(path, sysfs_path, sizeof(path));
 173         strlcat(path, devpath_real, sizeof(path));
 174         if (lstat(path, &statbuf) != 0) {
 175                 dbg("stat '%s' failed: %s", path, strerror(errno));
 176                 return NULL;
 177         }
 178         if (S_ISLNK(statbuf.st_mode)) {
 179                 if (sysfs_resolve_link(devpath_real, sizeof(devpath_real)) != 0)
 180                         return NULL;
 181
 182                 /* now look for device in cache after path translation */
 183                 list_for_each_entry(dev_loop, &dev_list, node) {
 184                         if (strcmp(dev_loop->devpath, devpath_real) == 0) {
 185                                 dbg("found in cache '%s'", dev_loop->devpath);
 186                                 return dev_loop;
 187                         }
 188                 }
 189         }
 190
 191         /* it is a new device */
 192         dbg("new uncached device '%s'", devpath_real);
 193         dev = malloc(sizeof(struct sysfs_device));
 194         if (dev == NULL)
 195                 return NULL;
 196         memset(dev, 0x00, sizeof(struct sysfs_device));
 197
 198         sysfs_device_set_values(dev, devpath_real, NULL, NULL);
 199
 200         /* get subsystem */
 201         if (strncmp(dev->devpath, "/class/", 7) == 0) {
 202                 strlcpy(dev->subsystem, &dev->devpath[7], sizeof(dev->subsystem));
 203                 pos = strchr(dev->subsystem, '/');
 204                 if (pos != NULL)
 205                         pos[0] = '\0';
 206                 else
 207                         dev->subsystem[0] = '\0';
 208         } else if (strncmp(dev->devpath, "/block/", 7) == 0) {
 209                 strlcpy(dev->subsystem, "block", sizeof(dev->subsystem));
 210         } else if (strncmp(dev->devpath, "/devices/", 9) == 0) {
 211                 /* get subsystem from "bus" link */
 212                 strlcpy(link_path, sysfs_path, sizeof(link_path));
 213                 strlcat(link_path, dev->devpath, sizeof(link_path));
 214                 strlcat(link_path, "/bus", sizeof(link_path));
 215                 len = readlink(link_path, link_target, sizeof(link_target));
 216                 if (len > 0) {
 217                         link_target[len] = '\0';
 218                         dbg("bus link '%s' points to '%s'", link_path, link_target);
 219                         pos = strrchr(link_target, '/');
 220                         if (pos != NULL)
 221                                 strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
 222                 } else {
 223                         /* get subsystem from "subsystem" link */
 224                         strlcpy(link_path, sysfs_path, sizeof(link_path));
 225                         strlcat(link_path, dev->devpath, sizeof(link_path));
 226                         strlcat(link_path, "/subsystem", sizeof(link_path));
 227                         len = readlink(link_path, link_target, sizeof(link_target));
 228                         if (len > 0) {
 229                                 link_target[len] = '\0';
 230                                 dbg("subsystem link '%s' points to '%s'", link_path, link_target);
 231                                 pos = strrchr(link_target, '/');
 232                                 if (pos != NULL)
 233                                         strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
 234                         }
 235                 }
 236                 /* get driver name */
 237                 strlcpy(link_path, sysfs_path, sizeof(link_path));
 238                 strlcat(link_path, dev->devpath, sizeof(link_path));
 239                 strlcat(link_path, "/driver", sizeof(link_path));
 240                 len = readlink(link_path, link_target, sizeof(link_target));
 241                 if (len > 0) {
 242                         link_target[len] = '\0';
 243                         dbg("driver link '%s' points to '%s'", link_path, link_target);
 244                         pos = strrchr(link_target, '/');
 245                         if (pos != NULL)
 246                                 strlcpy(dev->driver, &pos[1], sizeof(dev->driver));
 247                 }
 248         } else if (strncmp(dev->devpath, "/bus/", 5) == 0 && strstr(dev->devpath, "/drivers/")) {
 249                 strlcpy(dev->subsystem, "drivers", sizeof(dev->subsystem));
 250         } else if (strncmp(dev->devpath, "/module/", 8) == 0) {
 251                 strlcpy(dev->subsystem, "module", sizeof(dev->subsystem));
 252         }
 253
 254         dbg("add to cache 'devpath=%s', subsystem='%s', driver='%s'", dev->devpath, dev->subsystem, dev->driver);
 255         list_add(&dev->node, &dev_list);
 256
 257         return dev;
 258 }
 259
 260 struct sysfs_device *sysfs_device_get_parent(struct sysfs_device *dev)
 261 {
 262         char parent_devpath[PATH_SIZE];
 263         char *pos;
 264
 265         dbg("open '%s'", dev->devpath);
 266
 267         /* look if we already know the parent */
 268         if (dev->parent != NULL)
 269                 return dev->parent;
 270
 271         /* requesting a parent is only valid for devices */
 272         if ((strncmp(dev->devpath, "/devices/", 9) != 0) &&
 273             (strncmp(dev->devpath, "/class/", 7) != 0) &&
 274             (strncmp(dev->devpath, "/block/", 7) != 0))
 275                 return NULL;
 276
 277         strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
 278         dbg("'%s'", parent_devpath);
 279
 280         /* strip last element */
 281         pos = strrchr(parent_devpath, '/');
 282         if (pos == NULL || pos == parent_devpath)
 283                 return NULL;
 284         pos[0] = '\0';
 285
 286         /* are we at the top level of /devices */
 287         if (strcmp(parent_devpath, "/devices") == 0) {
 288                 dbg("/devices top level");
 289                 return NULL;
 290         }
 291
 292         /* at the top level of class/block we want to follow the "device" link */
 293         if (strcmp(parent_devpath, "/block") == 0) {
 294                 dbg("/block top level, look for device link");
 295                 goto device_link;
 296         }
 297         if (strncmp(parent_devpath, "/class", 6) == 0) {
 298                 pos = strrchr(parent_devpath, '/');
 299                 if (pos == &parent_devpath[6] || pos == parent_devpath) {
 300                         dbg("/class top level, look for device link");
 301                         goto device_link;
 302                 }
 303         }
 304         /* get parent and remember it */
 305         dev->parent = sysfs_device_get(parent_devpath);
 306         return dev->parent;
 307
 308 device_link:
 309         strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
 310         strlcat(parent_devpath, "/device", sizeof(parent_devpath));
 311         if (sysfs_resolve_link(parent_devpath, sizeof(parent_devpath)) != 0)
 312                 return NULL;
 313
 314         /* get parent and remember it */
 315         dev->parent = sysfs_device_get(parent_devpath);
 316         return dev->parent;
 317 }
 318
 319 struct sysfs_device *sysfs_device_get_parent_with_subsystem(struct sysfs_device *dev, const char *subsystem)
 320 {
 321         struct sysfs_device *dev_parent;
 322
 323         dev_parent = sysfs_device_get_parent(dev);
 324         while (dev_parent != NULL) {
 325                 if (strcmp(dev_parent->subsystem, subsystem) == 0)
 326                         return dev_parent;
 327                 dev_parent = sysfs_device_get_parent(dev_parent);
 328         }
 329         return NULL;
 330 }
 331
 332 char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
 333 {
 334         char path_full[PATH_SIZE];
 335         const char *path;
 336         char value[NAME_SIZE];
 337         struct sysfs_attr *attr_loop;
 338         struct sysfs_attr *attr;
 339         struct stat statbuf;
 340         int fd;
 341         ssize_t size;
 342         size_t sysfs_len;
 343
 344         dbg("open '%s'/'%s'", devpath, attr_name);
 345         sysfs_len = strlcpy(path_full, sysfs_path, sizeof(path_full));
 346         path = &path_full[sysfs_len];
 347         strlcat(path_full, devpath, sizeof(path_full));
 348         strlcat(path_full, "/", sizeof(path_full));
 349         strlcat(path_full, attr_name, sizeof(path_full));
 350
 351         /* look for attribute in cache */
 352         list_for_each_entry(attr_loop, &attr_list, node) {
 353                 if (strcmp(attr_loop->path, path) == 0) {
 354                         dbg("found in cache '%s'", attr_loop->path);
 355                         return attr_loop->value;
 356                 }
 357         }
 358
 359         /* store attribute in cache (also negatives are kept in cache) */
 360         dbg("new uncached attribute '%s'", path_full);
 361         attr = malloc(sizeof(struct sysfs_attr));
 362         if (attr == NULL)
 363                 return NULL;
 364         memset(attr, 0x00, sizeof(struct sysfs_attr));
 365         strlcpy(attr->path, path, sizeof(attr->path));
 366         dbg("add to cache '%s'", path_full);
 367         list_add(&attr->node, &attr_list);
 368
 369         if (lstat(path_full, &statbuf) != 0) {
 370                 dbg("stat '%s' failed: %s", path_full, strerror(errno));
 371                 goto out;
 372         }
 373
 374         if (S_ISLNK(statbuf.st_mode)) {
 375                 /* links return the last element of the target path */
 376                 char link_target[PATH_SIZE];
 377                 int len;
 378                 const char *pos;
 379
 380                 len = readlink(path_full, link_target, sizeof(link_target));
 381                 if (len > 0) {
 382                         link_target[len] = '\0';
 383                         pos = strrchr(link_target, '/');
 384                         if (pos != NULL) {
 385                                 dbg("cache '%s' with link value '%s'", path_full, value);
 386                                 strlcpy(attr->value_local, &pos[1], sizeof(attr->value_local));
 387                                 attr->value = attr->value_local;
 388                         }
 389                 }
 390                 goto out;
 391         }
 392
 393         /* skip directories */
 394         if (S_ISDIR(statbuf.st_mode))
 395                 goto out;
 396
 397         /* skip non-readable files */
 398         if ((statbuf.st_mode & S_IRUSR) == 0)
 399                 goto out;
 400
 401         /* read attribute value */
 402         fd = open(path_full, O_RDONLY);
 403         if (fd < 0) {
 404                 dbg("attribute '%s' does not exist", path_full);
 405                 goto out;
 406         }
 407         size = read(fd, value, sizeof(value));
 408         close(fd);
 409         if (size < 0)
 410                 goto out;
 411         if (size == sizeof(value))
 412                 goto out;
 413
 414         /* got a valid value, store and return it */
 415         value[size] = '\0';
 416         remove_trailing_chars(value, '\n');
 417         dbg("cache '%s' with attribute value '%s'", path_full, value);
 418         strlcpy(attr->value_local, value, sizeof(attr->value_local));
 419         attr->value = attr->value_local;
 420
 421 out:
 422         return attr->value;
 423 }