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[NAME_SIZE];
  44 };
  45
  46 int sysfs_init(void)
  47 {
  48         const char *env;
  49
  50         env = getenv("SYSFS_PATH");
  51         if (env) {
  52                 strlcpy(sysfs_path, env, sizeof(sysfs_path));
  53                 remove_trailing_chars(sysfs_path, '/');
  54         } else
  55                 strlcpy(sysfs_path, "/sys", sizeof(sysfs_path));
  56         dbg("sysfs_path='%s'", sysfs_path);
  57
  58         INIT_LIST_HEAD(&dev_list);
  59         INIT_LIST_HEAD(&attr_list);
  60         return 0;
  61 }
  62
  63 void sysfs_cleanup(void)
  64 {
  65         struct sysfs_attr *attr_loop;
  66         struct sysfs_attr *attr_temp;
  67         struct sysfs_device *dev_loop;
  68         struct sysfs_device *dev_temp;
  69
  70         list_for_each_entry_safe(attr_loop, attr_temp, &attr_list, node) {
  71                 list_del(&attr_loop->node);
  72                 free(attr_loop);
  73         }
  74
  75         list_for_each_entry_safe(dev_loop, dev_temp, &dev_list, node) {
  76                 list_del(&dev_loop->node);
  77                 free(dev_loop);
  78         }
  79 }
  80
  81 void sysfs_device_set_values(struct sysfs_device *dev, const char *devpath, const char *subsystem)
  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
  89         /* set kernel name */
  90         pos = strrchr(dev->devpath, '/');
  91         if (pos == NULL)
  92                 return;
  93
  94         strlcpy(dev->kernel_name, &pos[1], sizeof(dev->kernel_name));
  95         dbg("kernel_name='%s'", dev->kernel_name);
  96
  97         /* some devices have '!' in their name, change that to '/' */
  98         pos = dev->kernel_name;
  99         while (pos[0] != '\0') {
 100                 if (pos[0] == '!')
 101                         pos[0] = '/';
 102                 pos++;
 103         }
 104
 105         /* get kernel number */
 106         pos = &dev->kernel_name[strlen(dev->kernel_name)];
 107         while (isdigit(pos[-1]))
 108                 pos--;
 109         strlcpy(dev->kernel_number, pos, sizeof(dev->kernel_number));
 110         dbg("kernel_number='%s'", dev->kernel_number);
 111 }
 112
 113 struct sysfs_device *sysfs_device_get(const char *devpath)
 114 {
 115         char path[PATH_SIZE];
 116         char devpath_real[PATH_SIZE];
 117         struct sysfs_device *dev;
 118         struct sysfs_device *dev_loop;
 119         struct stat statbuf;
 120         char link_path[PATH_SIZE];
 121         char link_target[PATH_SIZE];
 122         int len;
 123         char *pos;
 124
 125         dbg("open '%s'", devpath);
 126         strlcpy(devpath_real, devpath, sizeof(devpath_real));
 127         remove_trailing_chars(devpath_real, '/');
 128
 129         strlcpy(path, sysfs_path, sizeof(path));
 130         strlcat(path, devpath_real, sizeof(path));
 131         if (lstat(path, &statbuf) != 0) {
 132                 dbg("stat '%s' failed: %s", path, strerror(errno));
 133                 return NULL;
 134         }
 135
 136         /* if we got a link, resolve it to the real device */
 137         if (S_ISLNK(statbuf.st_mode)) {
 138                 int i;
 139                 int back;
 140
 141                 len = readlink(path, link_target, sizeof(link_target));
 142                 if (len <= 0)
 143                         return NULL;
 144                 link_target[len] = '\0';
 145                 dbg("devpath link '%s' points to '%s'", path, link_target);
 146
 147                 for (back = 0; strncmp(&link_target[back * 3], "../", 3) == 0; back++)
 148                         ;
 149                 dbg("base '%s', tail '%s', back %i", devpath_real, &link_target[back * 3], back);
 150                 for (i = 0; i <= back; i++) {
 151                         pos = strrchr(devpath_real, '/');
 152                         if (pos == NULL)
 153                                 return NULL;
 154                         pos[0] = '\0';
 155                 }
 156                 dbg("after moving back '%s'", devpath_real);
 157                 strlcat(devpath_real, "/", sizeof(devpath_real));
 158                 strlcat(devpath_real, &link_target[back * 3], sizeof(devpath_real));
 159         }
 160
 161         /* look for device in cache */
 162         list_for_each_entry(dev_loop, &dev_list, node) {
 163                 if (strcmp(dev_loop->devpath, devpath_real) == 0) {
 164                         dbg("found in cache '%s'", dev_loop->devpath);
 165                         return dev_loop;
 166                 }
 167         }
 168
 169         /* new device */
 170         dbg("'%s'", devpath_real);
 171         dev = malloc(sizeof(struct sysfs_device));
 172         if (dev == NULL)
 173                 return NULL;
 174         memset(dev, 0x00, sizeof(struct sysfs_device));
 175
 176         sysfs_device_set_values(dev, devpath_real, NULL);
 177
 178         /* get subsystem */
 179         if (strncmp(dev->devpath, "/class/", 7) == 0) {
 180                 strlcpy(dev->subsystem, &dev->devpath[7], sizeof(dev->subsystem));
 181                 pos = strchr(dev->subsystem, '/');
 182                 if (pos != NULL)
 183                         pos[0] = '\0';
 184                 else
 185                         dev->subsystem[0] = '\0';
 186         } else if (strncmp(dev->devpath, "/block/", 7) == 0) {
 187                 strlcpy(dev->subsystem, "block", sizeof(dev->subsystem));
 188         } else if (strncmp(dev->devpath, "/devices/", 9) == 0) {
 189                 /* get subsystem from "bus" link */
 190                 strlcpy(link_path, sysfs_path, sizeof(link_path));
 191                 strlcat(link_path, dev->devpath, sizeof(link_path));
 192                 strlcat(link_path, "/bus", sizeof(link_path));
 193                 len = readlink(link_path, link_target, sizeof(link_target));
 194                 if (len > 0) {
 195                         link_target[len] = '\0';
 196                         dbg("bus link '%s' points to '%s'", link_path, link_target);
 197                         pos = strrchr(link_target, '/');
 198                         if (pos != NULL)
 199                                 strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
 200                 } else {
 201                         /* get subsystem from "subsystem" link */
 202                         strlcpy(link_path, sysfs_path, sizeof(link_path));
 203                         strlcat(link_path, dev->devpath, sizeof(link_path));
 204                         strlcat(link_path, "/subsystem", sizeof(link_path));
 205                         len = readlink(link_path, link_target, sizeof(link_target));
 206                         if (len > 0) {
 207                                 link_target[len] = '\0';
 208                                 dbg("subsystem link '%s' points to '%s'", link_path, link_target);
 209                                 pos = strrchr(link_target, '/');
 210                                 if (pos != NULL)
 211                                         strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
 212                         }
 213                 }
 214                 /* get driver name */
 215                 strlcpy(link_path, sysfs_path, sizeof(link_path));
 216                 strlcat(link_path, dev->devpath, sizeof(link_path));
 217                 strlcat(link_path, "/driver", sizeof(link_path));
 218                 len = readlink(link_path, link_target, sizeof(link_target));
 219                 if (len > 0) {
 220                         link_target[len] = '\0';
 221                         dbg("driver link '%s' points to '%s'", link_path, link_target);
 222                         pos = strrchr(link_target, '/');
 223                         if (pos != NULL)
 224                                 strlcpy(dev->driver, &pos[1], sizeof(dev->driver));
 225                 }
 226         } else if (strncmp(dev->devpath, "/bus/", 5) == 0 && strstr(dev->devpath, "/drivers/")) {
 227                 strlcpy(dev->subsystem, "drivers", sizeof(dev->subsystem));
 228         } else if (strncmp(dev->devpath, "/module/", 8) == 0) {
 229                 strlcpy(dev->subsystem, "module", sizeof(dev->subsystem));
 230         }
 231
 232         dbg("add to cache 'devpath=%s', subsystem='%s', driver='%s'", dev->devpath, dev->subsystem, dev->driver);
 233         list_add(&dev->node, &dev_list);
 234
 235         return dev;
 236 }
 237
 238 struct sysfs_device *sysfs_device_get_parent(struct sysfs_device *dev)
 239 {
 240         char parent_devpath[PATH_SIZE];
 241         char device_link[PATH_SIZE];
 242         char device_link_target[PATH_SIZE];
 243         char *pos;
 244         int i;
 245         int len;
 246         int back;
 247
 248         /* requesting a parent is only valid for devices */
 249         if ((strncmp(dev->devpath, "/devices/", 9) != 0) &&
 250             (strncmp(dev->devpath, "/class/", 7) != 0) &&
 251             (strncmp(dev->devpath, "/block/", 7) != 0))
 252                 return NULL;
 253
 254         strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
 255         dbg("'%s'", parent_devpath);
 256
 257         /* strip last element */
 258         pos = strrchr(parent_devpath, '/');
 259         if (pos == NULL || pos == parent_devpath)
 260                 return NULL;
 261         pos[0] = '\0';
 262
 263         /* are we at the top level */
 264         if (strcmp(parent_devpath, "/devices") == 0) {
 265                 dbg("/devices top level");
 266                 return NULL;
 267         }
 268
 269         /* at the top level we may follow the "device" link */
 270         if (strcmp(parent_devpath, "/block") == 0) {
 271                 dbg("/block top level, look for device link");
 272                 goto device_link;
 273         }
 274
 275         if (strncmp(parent_devpath, "/class", 6) == 0) {
 276                 pos = strrchr(parent_devpath, '/');
 277                 if (pos == &parent_devpath[6] || pos == parent_devpath) {
 278                         dbg("/class top level, look for device link");
 279                         goto device_link;
 280                 }
 281         }
 282         return sysfs_device_get(parent_devpath);
 283
 284 device_link:
 285         strlcpy(device_link, sysfs_path, sizeof(device_link));
 286         strlcat(device_link, dev->devpath, sizeof(device_link));
 287         strlcat(device_link, "/device", sizeof(device_link));
 288         len = readlink(device_link, device_link_target, sizeof(device_link_target));
 289         if (len < 0)
 290                 return NULL;
 291         device_link_target[len] = '\0';
 292         dbg("device link '%s' points to '%s'", device_link, device_link_target);
 293
 294         for (back = 0; strncmp(&device_link_target[back * 3], "../", 3) == 0; back++)
 295                 ;
 296         strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
 297         dbg("base='%s', tail='%s', back=%i", parent_devpath, &device_link_target[back * 3], back);
 298         for (i = 0; i < back; i++) {
 299                 pos = strrchr(parent_devpath, '/');
 300                 if (pos == NULL)
 301                         return NULL;
 302                 pos[0] = '\0';
 303         }
 304         dbg("after moving back '%s'", parent_devpath);
 305         strlcat(parent_devpath, "/", sizeof(parent_devpath));
 306         strlcat(parent_devpath, &device_link_target[back * 3], sizeof(parent_devpath));
 307         return sysfs_device_get(parent_devpath);
 308 }
 309
 310 struct sysfs_device *sysfs_device_get_parent_with_subsystem(struct sysfs_device *dev, const char *subsystem)
 311 {
 312         struct sysfs_device *dev_parent;
 313
 314         dev_parent = sysfs_device_get_parent(dev);
 315         while (dev_parent != NULL) {
 316                 if (strcmp(dev_parent->subsystem, subsystem) == 0)
 317                         return dev_parent;
 318                 dev_parent = sysfs_device_get_parent(dev_parent);
 319         }
 320         return NULL;
 321 }
 322
 323 char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
 324 {
 325         char path_full[PATH_SIZE];
 326         const char *path;
 327         char value[NAME_SIZE];
 328         struct sysfs_attr *attr_loop;
 329         struct sysfs_attr *attr;
 330         int fd;
 331         ssize_t size;
 332         size_t sysfs_len;
 333
 334         sysfs_len = strlcpy(path_full, sysfs_path, sizeof(path_full));
 335         path = &path_full[sysfs_len];
 336         strlcat(path_full, devpath, sizeof(path_full));
 337         strlcat(path_full, "/", sizeof(path_full));
 338         strlcat(path_full, attr_name, sizeof(path_full));
 339
 340         /* look for attribute in cache */
 341         list_for_each_entry(attr_loop, &attr_list, node) {
 342                 if (strcmp(attr_loop->path, path) == 0) {
 343                         dbg("found in cache '%s'", attr_loop->path);
 344                         return attr_loop->value;
 345                 }
 346         }
 347
 348         /* read attribute value */
 349         fd = open(path_full, O_RDONLY);
 350         if (fd < 0)
 351                 return NULL;
 352         size = read(fd, value, sizeof(value));
 353         close(fd);
 354         if (size < 0)
 355                 return NULL;
 356         if (size == sizeof(value))
 357                 return NULL;
 358         value[size] = '\0';
 359         remove_trailing_chars(value, '\n');
 360
 361         /* store attribute in cache */
 362         attr = malloc(sizeof(struct sysfs_attr));
 363         if (attr == NULL)
 364                 return NULL;
 365         strlcpy(attr->path, path, sizeof(attr->path));
 366         strlcpy(attr->value, value, sizeof(attr->value));
 367         dbg("add to cache '%s' '%s'", attr->path, attr->value);
 368         list_add(&attr->node, &attr_list);
 369
 370         return attr->value;
 371 }