udev_sysfs.c

   1 /*
   2  * udev_sysfs.c - sysfs access
   3  *
   4  * Copyright (C) 2005 Kay Sievers <kay.sievers@vrfy.org>
   5  *
   6  *      This program is free software; you can redistribute it and/or modify it
   7  *      under the terms of the GNU General Public License as published by the
   8  *      Free Software Foundation version 2 of the License.
   9  *
  10  *      This program is distributed in the hope that it will be useful, but
  11  *      WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  *      General Public License for more details.
  14  *
  15  *      You should have received a copy of the GNU General Public License along
  16  *      with this program; if not, write to the Free Software Foundation, Inc.,
  17  *      675 Mass Ave, Cambridge, MA 02139, USA.
  18  *
  19  */
  20
  21
  22 #include <stdlib.h>
  23 #include <stdio.h>
  24 #include <stddef.h>
  25 #include <unistd.h>
  26 #include <fcntl.h>
  27 #include <ctype.h>
  28 #include <errno.h>
  29 #include <sys/stat.h>
  30
  31 #include "udev.h"
  32
  33 char sysfs_path[PATH_SIZE];
  34
  35 /* device cache */
  36 static LIST_HEAD(dev_list);
  37
  38 /* attribute value cache */
  39 static LIST_HEAD(attr_list);
  40 struct sysfs_attr {
  41         struct list_head node;
  42         char path[PATH_SIZE];
  43         char *value;                    /* points to value_local if value is cached */
  44         char value_local[NAME_SIZE];
  45 };
  46
  47 int sysfs_init(void)
  48 {
  49         const char *env;
  50
  51         env = getenv("SYSFS_PATH");
  52         if (env) {
  53                 strlcpy(sysfs_path, env, sizeof(sysfs_path));
  54                 remove_trailing_chars(sysfs_path, '/');
  55         } else
  56                 strlcpy(sysfs_path, "/sys", sizeof(sysfs_path));
  57         dbg("sysfs_path='%s'", sysfs_path);
  58
  59         INIT_LIST_HEAD(&dev_list);
  60         INIT_LIST_HEAD(&attr_list);
  61         return 0;
  62 }
  63
  64 void sysfs_cleanup(void)
  65 {
  66         struct sysfs_attr *attr_loop;
  67         struct sysfs_attr *attr_temp;
  68         struct sysfs_device *dev_loop;
  69         struct sysfs_device *dev_temp;
  70
  71         list_for_each_entry_safe(attr_loop, attr_temp, &attr_list, node) {
  72                 list_del(&attr_loop->node);
  73                 free(attr_loop);
  74         }
  75
  76         list_for_each_entry_safe(dev_loop, dev_temp, &dev_list, node) {
  77                 list_del(&dev_loop->node);
  78                 free(dev_loop);
  79         }
  80 }
  81
  82 void sysfs_device_set_values(struct sysfs_device *dev, const char *devpath,
  83                              const char *subsystem, const char *driver)
  84 {
  85         char *pos;
  86
  87         strlcpy(dev->devpath, devpath, sizeof(dev->devpath));
  88         if (subsystem != NULL)
  89                 strlcpy(dev->subsystem, subsystem, sizeof(dev->subsystem));
  90         if (driver != NULL)
  91                 strlcpy(dev->driver, driver, sizeof(dev->driver));
  92
  93         /* set kernel name */
  94         pos = strrchr(dev->devpath, '/');
  95         if (pos == NULL)
  96                 return;
  97
  98         strlcpy(dev->kernel, &pos[1], sizeof(dev->kernel));
  99         dbg("kernel='%s'", dev->kernel);
 100
 101         /* some devices have '!' in their name, change that to '/' */
 102         pos = dev->kernel;
 103         while (pos[0] != '\0') {
 104                 if (pos[0] == '!')
 105                         pos[0] = '/';
 106                 pos++;
 107         }
 108
 109         /* get kernel number */
 110         pos = &dev->kernel[strlen(dev->kernel)];
 111         while (isdigit(pos[-1]))
 112                 pos--;
 113         strlcpy(dev->kernel_number, pos, sizeof(dev->kernel_number));
 114         dbg("kernel_number='%s'", dev->kernel_number);
 115 }
 116
 117 struct sysfs_device *sysfs_device_get(const char *devpath)
 118 {
 119         char path[PATH_SIZE];
 120         char devpath_real[PATH_SIZE];
 121         struct sysfs_device *dev;
 122         struct sysfs_device *dev_loop;
 123         struct stat statbuf;
 124         char link_path[PATH_SIZE];
 125         char link_target[PATH_SIZE];
 126         int len;
 127         char *pos;
 128
 129         dbg("open '%s'", devpath);
 130         strlcpy(devpath_real, devpath, sizeof(devpath_real));
 131         remove_trailing_chars(devpath_real, '/');
 132
 133         /* look for device already in cache (we never put an untranslated path in the cache) */
 134         list_for_each_entry(dev_loop, &dev_list, node) {
 135                 if (strcmp(dev_loop->devpath, devpath_real) == 0) {
 136                         dbg("found in cache '%s'", dev_loop->devpath);
 137                         return dev_loop;
 138                 }
 139         }
 140
 141         /* if we got a link, resolve it to the real device */
 142         strlcpy(path, sysfs_path, sizeof(path));
 143         strlcat(path, devpath_real, sizeof(path));
 144         if (lstat(path, &statbuf) != 0) {
 145                 dbg("stat '%s' failed: %s", path, strerror(errno));
 146                 return NULL;
 147         }
 148         if (S_ISLNK(statbuf.st_mode)) {
 149                 int i;
 150                 int back;
 151
 152                 len = readlink(path, link_target, sizeof(link_target));
 153                 if (len <= 0)
 154                         return NULL;
 155                 link_target[len] = '\0';
 156                 dbg("devpath link '%s' points to '%s'", path, link_target);
 157
 158                 for (back = 0; strncmp(&link_target[back * 3], "../", 3) == 0; back++)
 159                         ;
 160                 dbg("base '%s', tail '%s', back %i", devpath_real, &link_target[back * 3], back);
 161                 for (i = 0; i <= back; i++) {
 162                         pos = strrchr(devpath_real, '/');
 163                         if (pos == NULL)
 164                                 return NULL;
 165                         pos[0] = '\0';
 166                 }
 167                 dbg("after moving back '%s'", devpath_real);
 168                 strlcat(devpath_real, "/", sizeof(devpath_real));
 169                 strlcat(devpath_real, &link_target[back * 3], sizeof(devpath_real));
 170
 171                 /* now look for device in cache after path translation */
 172                 list_for_each_entry(dev_loop, &dev_list, node) {
 173                         if (strcmp(dev_loop->devpath, devpath_real) == 0) {
 174                                 dbg("found in cache '%s'", dev_loop->devpath);
 175                                 return dev_loop;
 176                         }
 177                 }
 178         }
 179
 180         /* it is a new device */
 181         dbg("new uncached device '%s'", devpath_real);
 182         dev = malloc(sizeof(struct sysfs_device));
 183         if (dev == NULL)
 184                 return NULL;
 185         memset(dev, 0x00, sizeof(struct sysfs_device));
 186
 187         sysfs_device_set_values(dev, devpath_real, NULL, NULL);
 188
 189         /* get subsystem */
 190         if (strncmp(dev->devpath, "/class/", 7) == 0) {
 191                 strlcpy(dev->subsystem, &dev->devpath[7], sizeof(dev->subsystem));
 192                 pos = strchr(dev->subsystem, '/');
 193                 if (pos != NULL)
 194                         pos[0] = '\0';
 195                 else
 196                         dev->subsystem[0] = '\0';
 197         } else if (strncmp(dev->devpath, "/block/", 7) == 0) {
 198                 strlcpy(dev->subsystem, "block", sizeof(dev->subsystem));
 199         } else if (strncmp(dev->devpath, "/devices/", 9) == 0) {
 200                 /* get subsystem from "bus" link */
 201                 strlcpy(link_path, sysfs_path, sizeof(link_path));
 202                 strlcat(link_path, dev->devpath, sizeof(link_path));
 203                 strlcat(link_path, "/bus", sizeof(link_path));
 204                 len = readlink(link_path, link_target, sizeof(link_target));
 205                 if (len > 0) {
 206                         link_target[len] = '\0';
 207                         dbg("bus link '%s' points to '%s'", link_path, link_target);
 208                         pos = strrchr(link_target, '/');
 209                         if (pos != NULL)
 210                                 strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
 211                 } else {
 212                         /* get subsystem from "subsystem" link */
 213                         strlcpy(link_path, sysfs_path, sizeof(link_path));
 214                         strlcat(link_path, dev->devpath, sizeof(link_path));
 215                         strlcat(link_path, "/subsystem", sizeof(link_path));
 216                         len = readlink(link_path, link_target, sizeof(link_target));
 217                         if (len > 0) {
 218                                 link_target[len] = '\0';
 219                                 dbg("subsystem link '%s' points to '%s'", link_path, link_target);
 220                                 pos = strrchr(link_target, '/');
 221                                 if (pos != NULL)
 222                                         strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
 223                         }
 224                 }
 225                 /* get driver name */
 226                 strlcpy(link_path, sysfs_path, sizeof(link_path));
 227                 strlcat(link_path, dev->devpath, sizeof(link_path));
 228                 strlcat(link_path, "/driver", sizeof(link_path));
 229                 len = readlink(link_path, link_target, sizeof(link_target));
 230                 if (len > 0) {
 231                         link_target[len] = '\0';
 232                         dbg("driver link '%s' points to '%s'", link_path, link_target);
 233                         pos = strrchr(link_target, '/');
 234                         if (pos != NULL)
 235                                 strlcpy(dev->driver, &pos[1], sizeof(dev->driver));
 236                 }
 237         } else if (strncmp(dev->devpath, "/bus/", 5) == 0 && strstr(dev->devpath, "/drivers/")) {
 238                 strlcpy(dev->subsystem, "drivers", sizeof(dev->subsystem));
 239         } else if (strncmp(dev->devpath, "/module/", 8) == 0) {
 240                 strlcpy(dev->subsystem, "module", sizeof(dev->subsystem));
 241         }
 242
 243         dbg("add to cache 'devpath=%s', subsystem='%s', driver='%s'", dev->devpath, dev->subsystem, dev->driver);
 244         list_add(&dev->node, &dev_list);
 245
 246         return dev;
 247 }
 248
 249 struct sysfs_device *sysfs_device_get_parent(struct sysfs_device *dev)
 250 {
 251         char parent_devpath[PATH_SIZE];
 252         char device_link[PATH_SIZE];
 253         char device_link_target[PATH_SIZE];
 254         char *pos;
 255         int i;
 256         int len;
 257         int back;
 258
 259         dbg("open '%s'", dev->devpath);
 260
 261         /* look if we already know the parent */
 262         if (dev->parent != NULL)
 263                 return dev->parent;
 264
 265         /* requesting a parent is only valid for devices */
 266         if ((strncmp(dev->devpath, "/devices/", 9) != 0) &&
 267             (strncmp(dev->devpath, "/class/", 7) != 0) &&
 268             (strncmp(dev->devpath, "/block/", 7) != 0))
 269                 return NULL;
 270
 271         strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
 272         dbg("'%s'", parent_devpath);
 273
 274         /* strip last element */
 275         pos = strrchr(parent_devpath, '/');
 276         if (pos == NULL || pos == parent_devpath)
 277                 return NULL;
 278         pos[0] = '\0';
 279
 280         /* are we at the top level of /devices */
 281         if (strcmp(parent_devpath, "/devices") == 0) {
 282                 dbg("/devices top level");
 283                 return NULL;
 284         }
 285
 286         /* at the top level of class/block we want to follow the "device" link */
 287         if (strcmp(parent_devpath, "/block") == 0) {
 288                 dbg("/block top level, look for device link");
 289                 goto device_link;
 290         }
 291         if (strncmp(parent_devpath, "/class", 6) == 0) {
 292                 pos = strrchr(parent_devpath, '/');
 293                 if (pos == &parent_devpath[6] || pos == parent_devpath) {
 294                         dbg("/class top level, look for device link");
 295                         goto device_link;
 296                 }
 297         }
 298         /* get parent and remember it */
 299         dev->parent = sysfs_device_get(parent_devpath);
 300         return dev->parent;
 301
 302 device_link:
 303         strlcpy(device_link, sysfs_path, sizeof(device_link));
 304         strlcat(device_link, dev->devpath, sizeof(device_link));
 305         strlcat(device_link, "/device", sizeof(device_link));
 306         len = readlink(device_link, device_link_target, sizeof(device_link_target));
 307         if (len < 0)
 308                 return NULL;
 309         device_link_target[len] = '\0';
 310         dbg("device link '%s' points to '%s'", device_link, device_link_target);
 311
 312         for (back = 0; strncmp(&device_link_target[back * 3], "../", 3) == 0; back++)
 313                 ;
 314         strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
 315         dbg("base='%s', tail='%s', back=%i", parent_devpath, &device_link_target[back * 3], back);
 316         for (i = 0; i < back; i++) {
 317                 pos = strrchr(parent_devpath, '/');
 318                 if (pos == NULL)
 319                         return NULL;
 320                 pos[0] = '\0';
 321         }
 322         dbg("after moving back '%s'", parent_devpath);
 323         strlcat(parent_devpath, "/", sizeof(parent_devpath));
 324         strlcat(parent_devpath, &device_link_target[back * 3], sizeof(parent_devpath));
 325
 326         /* get parent and remember it */
 327         dev->parent = sysfs_device_get(parent_devpath);
 328         return dev->parent;
 329 }
 330
 331 struct sysfs_device *sysfs_device_get_parent_with_subsystem(struct sysfs_device *dev, const char *subsystem)
 332 {
 333         struct sysfs_device *dev_parent;
 334
 335         dev_parent = sysfs_device_get_parent(dev);
 336         while (dev_parent != NULL) {
 337                 if (strcmp(dev_parent->subsystem, subsystem) == 0)
 338                         return dev_parent;
 339                 dev_parent = sysfs_device_get_parent(dev_parent);
 340         }
 341         return NULL;
 342 }
 343
 344 char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
 345 {
 346         char path_full[PATH_SIZE];
 347         const char *path;
 348         char value[NAME_SIZE];
 349         struct sysfs_attr *attr_loop;
 350         struct sysfs_attr *attr;
 351         int fd;
 352         ssize_t size;
 353         size_t sysfs_len;
 354
 355         dbg("open '%s'/'%s'", devpath, attr_name);
 356         sysfs_len = strlcpy(path_full, sysfs_path, sizeof(path_full));
 357         path = &path_full[sysfs_len];
 358         strlcat(path_full, devpath, sizeof(path_full));
 359         strlcat(path_full, "/", sizeof(path_full));
 360         strlcat(path_full, attr_name, sizeof(path_full));
 361
 362         /* look for attribute in cache */
 363         list_for_each_entry(attr_loop, &attr_list, node) {
 364                 if (strcmp(attr_loop->path, path) == 0) {
 365                         dbg("found in cache '%s'", attr_loop->path);
 366                         return attr_loop->value;
 367                 }
 368         }
 369
 370         /* store attribute in cache (also negatives are kept in cache) */
 371         dbg("new uncached attribute '%s'", path_full);
 372         attr = malloc(sizeof(struct sysfs_attr));
 373         if (attr == NULL)
 374                 return NULL;
 375         memset(attr, 0x00, sizeof(struct sysfs_attr));
 376         strlcpy(attr->path, path, sizeof(attr->path));
 377         dbg("add to cache '%s'", path_full);
 378         list_add(&attr->node, &attr_list);
 379
 380         /* read attribute value */
 381         fd = open(path_full, O_RDONLY);
 382         if (fd < 0) {
 383                 dbg("attribute '%s' does not exist", path_full);
 384                 goto out;
 385         }
 386         size = read(fd, value, sizeof(value));
 387         close(fd);
 388         if (size < 0)
 389                 goto out;
 390         if (size == sizeof(value))
 391                 goto out;
 392
 393         /* got a valid value, store and return it */
 394         value[size] = '\0';
 395         remove_trailing_chars(value, '\n');
 396         dbg("cache '%s' with value '%s'", path_full, value);
 397         strlcpy(attr->value_local, value, sizeof(attr->value_local));
 398         attr->value = attr->value_local;
 399
 400 out:
 401         return attr->value;
 402 }