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, const char *subsystem)
  83 {
  84         char *pos;
  85
  86         strlcpy(dev->devpath, devpath, sizeof(dev->devpath));
  87         if (subsystem != NULL)
  88                 strlcpy(dev->subsystem, subsystem, sizeof(dev->subsystem));
  89
  90         /* set kernel name */
  91         pos = strrchr(dev->devpath, '/');
  92         if (pos == NULL)
  93                 return;
  94
  95         strlcpy(dev->kernel_name, &pos[1], sizeof(dev->kernel_name));
  96         dbg("kernel_name='%s'", dev->kernel_name);
  97
  98         /* some devices have '!' in their name, change that to '/' */
  99         pos = dev->kernel_name;
 100         while (pos[0] != '\0') {
 101                 if (pos[0] == '!')
 102                         pos[0] = '/';
 103                 pos++;
 104         }
 105
 106         /* get kernel number */
 107         pos = &dev->kernel_name[strlen(dev->kernel_name)];
 108         while (isdigit(pos[-1]))
 109                 pos--;
 110         strlcpy(dev->kernel_number, pos, sizeof(dev->kernel_number));
 111         dbg("kernel_number='%s'", dev->kernel_number);
 112 }
 113
 114 struct sysfs_device *sysfs_device_get(const char *devpath)
 115 {
 116         char path[PATH_SIZE];
 117         char devpath_real[PATH_SIZE];
 118         struct sysfs_device *dev;
 119         struct sysfs_device *dev_loop;
 120         struct stat statbuf;
 121         char link_path[PATH_SIZE];
 122         char link_target[PATH_SIZE];
 123         int len;
 124         char *pos;
 125
 126         dbg("open '%s'", devpath);
 127         strlcpy(devpath_real, devpath, sizeof(devpath_real));
 128         remove_trailing_chars(devpath_real, '/');
 129
 130         /* look for device already in cache (we never put an untranslated path in the cache) */
 131         list_for_each_entry(dev_loop, &dev_list, node) {
 132                 if (strcmp(dev_loop->devpath, devpath_real) == 0) {
 133                         dbg("found in cache '%s'", dev_loop->devpath);
 134                         return dev_loop;
 135                 }
 136         }
 137
 138         /* if we got a link, resolve it to the real device */
 139         strlcpy(path, sysfs_path, sizeof(path));
 140         strlcat(path, devpath_real, sizeof(path));
 141         if (lstat(path, &statbuf) != 0) {
 142                 dbg("stat '%s' failed: %s", path, strerror(errno));
 143                 return NULL;
 144         }
 145         if (S_ISLNK(statbuf.st_mode)) {
 146                 int i;
 147                 int back;
 148
 149                 len = readlink(path, link_target, sizeof(link_target));
 150                 if (len <= 0)
 151                         return NULL;
 152                 link_target[len] = '\0';
 153                 dbg("devpath link '%s' points to '%s'", path, link_target);
 154
 155                 for (back = 0; strncmp(&link_target[back * 3], "../", 3) == 0; back++)
 156                         ;
 157                 dbg("base '%s', tail '%s', back %i", devpath_real, &link_target[back * 3], back);
 158                 for (i = 0; i <= back; i++) {
 159                         pos = strrchr(devpath_real, '/');
 160                         if (pos == NULL)
 161                                 return NULL;
 162                         pos[0] = '\0';
 163                 }
 164                 dbg("after moving back '%s'", devpath_real);
 165                 strlcat(devpath_real, "/", sizeof(devpath_real));
 166                 strlcat(devpath_real, &link_target[back * 3], sizeof(devpath_real));
 167
 168                 /* now look for device in cache after path translation */
 169                 list_for_each_entry(dev_loop, &dev_list, node) {
 170                         if (strcmp(dev_loop->devpath, devpath_real) == 0) {
 171                                 dbg("found in cache '%s'", dev_loop->devpath);
 172                                 return dev_loop;
 173                         }
 174                 }
 175         }
 176
 177         /* it is a new device */
 178         dbg("'%s'", devpath_real);
 179         dev = malloc(sizeof(struct sysfs_device));
 180         if (dev == NULL)
 181                 return NULL;
 182         memset(dev, 0x00, sizeof(struct sysfs_device));
 183
 184         sysfs_device_set_values(dev, devpath_real, NULL);
 185
 186         /* get subsystem */
 187         if (strncmp(dev->devpath, "/class/", 7) == 0) {
 188                 strlcpy(dev->subsystem, &dev->devpath[7], sizeof(dev->subsystem));
 189                 pos = strchr(dev->subsystem, '/');
 190                 if (pos != NULL)
 191                         pos[0] = '\0';
 192                 else
 193                         dev->subsystem[0] = '\0';
 194         } else if (strncmp(dev->devpath, "/block/", 7) == 0) {
 195                 strlcpy(dev->subsystem, "block", sizeof(dev->subsystem));
 196         } else if (strncmp(dev->devpath, "/devices/", 9) == 0) {
 197                 /* get subsystem from "bus" link */
 198                 strlcpy(link_path, sysfs_path, sizeof(link_path));
 199                 strlcat(link_path, dev->devpath, sizeof(link_path));
 200                 strlcat(link_path, "/bus", sizeof(link_path));
 201                 len = readlink(link_path, link_target, sizeof(link_target));
 202                 if (len > 0) {
 203                         link_target[len] = '\0';
 204                         dbg("bus link '%s' points to '%s'", link_path, link_target);
 205                         pos = strrchr(link_target, '/');
 206                         if (pos != NULL)
 207                                 strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
 208                 } else {
 209                         /* get subsystem from "subsystem" link */
 210                         strlcpy(link_path, sysfs_path, sizeof(link_path));
 211                         strlcat(link_path, dev->devpath, sizeof(link_path));
 212                         strlcat(link_path, "/subsystem", sizeof(link_path));
 213                         len = readlink(link_path, link_target, sizeof(link_target));
 214                         if (len > 0) {
 215                                 link_target[len] = '\0';
 216                                 dbg("subsystem link '%s' points to '%s'", link_path, link_target);
 217                                 pos = strrchr(link_target, '/');
 218                                 if (pos != NULL)
 219                                         strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
 220                         }
 221                 }
 222                 /* get driver name */
 223                 strlcpy(link_path, sysfs_path, sizeof(link_path));
 224                 strlcat(link_path, dev->devpath, sizeof(link_path));
 225                 strlcat(link_path, "/driver", sizeof(link_path));
 226                 len = readlink(link_path, link_target, sizeof(link_target));
 227                 if (len > 0) {
 228                         link_target[len] = '\0';
 229                         dbg("driver link '%s' points to '%s'", link_path, link_target);
 230                         pos = strrchr(link_target, '/');
 231                         if (pos != NULL)
 232                                 strlcpy(dev->driver, &pos[1], sizeof(dev->driver));
 233                 }
 234         } else if (strncmp(dev->devpath, "/bus/", 5) == 0 && strstr(dev->devpath, "/drivers/")) {
 235                 strlcpy(dev->subsystem, "drivers", sizeof(dev->subsystem));
 236         } else if (strncmp(dev->devpath, "/module/", 8) == 0) {
 237                 strlcpy(dev->subsystem, "module", sizeof(dev->subsystem));
 238         }
 239
 240         dbg("add to cache 'devpath=%s', subsystem='%s', driver='%s'", dev->devpath, dev->subsystem, dev->driver);
 241         list_add(&dev->node, &dev_list);
 242
 243         return dev;
 244 }
 245
 246 struct sysfs_device *sysfs_device_get_parent(struct sysfs_device *dev)
 247 {
 248         char parent_devpath[PATH_SIZE];
 249         char device_link[PATH_SIZE];
 250         char device_link_target[PATH_SIZE];
 251         char *pos;
 252         int i;
 253         int len;
 254         int back;
 255
 256         if (dev->parent != NULL)
 257                 return dev->parent;
 258
 259         /* requesting a parent is only valid for devices */
 260         if ((strncmp(dev->devpath, "/devices/", 9) != 0) &&
 261             (strncmp(dev->devpath, "/class/", 7) != 0) &&
 262             (strncmp(dev->devpath, "/block/", 7) != 0))
 263                 return NULL;
 264
 265         strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
 266         dbg("'%s'", parent_devpath);
 267
 268         /* strip last element */
 269         pos = strrchr(parent_devpath, '/');
 270         if (pos == NULL || pos == parent_devpath)
 271                 return NULL;
 272         pos[0] = '\0';
 273
 274         /* are we at the top level */
 275         if (strcmp(parent_devpath, "/devices") == 0) {
 276                 dbg("/devices top level");
 277                 return NULL;
 278         }
 279
 280         /* at the top level of class/block we want to follow the "device" link */
 281         if (strcmp(parent_devpath, "/block") == 0) {
 282                 dbg("/block top level, look for device link");
 283                 goto device_link;
 284         }
 285         if (strncmp(parent_devpath, "/class", 6) == 0) {
 286                 pos = strrchr(parent_devpath, '/');
 287                 if (pos == &parent_devpath[6] || pos == parent_devpath) {
 288                         dbg("/class top level, look for device link");
 289                         goto device_link;
 290                 }
 291         }
 292         dev->parent = sysfs_device_get(parent_devpath);
 293         return dev->parent;
 294
 295 device_link:
 296         strlcpy(device_link, sysfs_path, sizeof(device_link));
 297         strlcat(device_link, dev->devpath, sizeof(device_link));
 298         strlcat(device_link, "/device", sizeof(device_link));
 299         len = readlink(device_link, device_link_target, sizeof(device_link_target));
 300         if (len < 0)
 301                 return NULL;
 302         device_link_target[len] = '\0';
 303         dbg("device link '%s' points to '%s'", device_link, device_link_target);
 304
 305         for (back = 0; strncmp(&device_link_target[back * 3], "../", 3) == 0; back++)
 306                 ;
 307         strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
 308         dbg("base='%s', tail='%s', back=%i", parent_devpath, &device_link_target[back * 3], back);
 309         for (i = 0; i < back; i++) {
 310                 pos = strrchr(parent_devpath, '/');
 311                 if (pos == NULL)
 312                         return NULL;
 313                 pos[0] = '\0';
 314         }
 315         dbg("after moving back '%s'", parent_devpath);
 316         strlcat(parent_devpath, "/", sizeof(parent_devpath));
 317         strlcat(parent_devpath, &device_link_target[back * 3], sizeof(parent_devpath));
 318
 319         dev->parent = sysfs_device_get(parent_devpath);
 320         return dev->parent;
 321 }
 322
 323 struct sysfs_device *sysfs_device_get_parent_with_subsystem(struct sysfs_device *dev, const char *subsystem)
 324 {
 325         struct sysfs_device *dev_parent;
 326
 327         dev_parent = sysfs_device_get_parent(dev);
 328         while (dev_parent != NULL) {
 329                 if (strcmp(dev_parent->subsystem, subsystem) == 0)
 330                         return dev_parent;
 331                 dev_parent = sysfs_device_get_parent(dev_parent);
 332         }
 333         return NULL;
 334 }
 335
 336 char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
 337 {
 338         char path_full[PATH_SIZE];
 339         const char *path;
 340         char value[NAME_SIZE];
 341         struct sysfs_attr *attr_loop;
 342         struct sysfs_attr *attr;
 343         int fd;
 344         ssize_t size;
 345         size_t sysfs_len;
 346
 347         sysfs_len = strlcpy(path_full, sysfs_path, sizeof(path_full));
 348         path = &path_full[sysfs_len];
 349         strlcat(path_full, devpath, sizeof(path_full));
 350         strlcat(path_full, "/", sizeof(path_full));
 351         strlcat(path_full, attr_name, sizeof(path_full));
 352
 353         /* look for attribute in cache */
 354         list_for_each_entry(attr_loop, &attr_list, node) {
 355                 if (strcmp(attr_loop->path, path) == 0) {
 356                         dbg("found in cache '%s'", attr_loop->path);
 357                         return attr_loop->value;
 358                 }
 359         }
 360
 361         /* store attribute in cache (also negatives are kept in cache) */
 362         attr = malloc(sizeof(struct sysfs_attr));
 363         if (attr == NULL)
 364                 return NULL;
 365         memset(attr, 0x00, sizeof(struct sysfs_attr));
 366         strlcpy(attr->path, path, sizeof(attr->path));
 367         dbg("add to cache '%s' '%s'", attr->path, attr->value);
 368         list_add(&attr->node, &attr_list);
 369
 370         /* read attribute value */
 371         fd = open(path_full, O_RDONLY);
 372         if (fd < 0)
 373                 goto out;
 374         size = read(fd, value, sizeof(value));
 375         close(fd);
 376         if (size < 0)
 377                 goto out;
 378         if (size == sizeof(value))
 379                 goto out;
 380
 381         /* got a valid value, store and return it */
 382         value[size] = '\0';
 383         remove_trailing_chars(value, '\n');
 384         strlcpy(attr->value_local, value, sizeof(attr->value_local));
 385         attr->value = attr->value_local;
 386
 387 out:
 388         return attr->value;
 389 }