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
  30 #include "udev.h"
  31
  32 char sysfs_path[PATH_SIZE];
  33
  34 /* device cache */
  35 static LIST_HEAD(dev_list);
  36
  37 /* attribute value cache */
  38 static LIST_HEAD(attr_list);
  39 struct sysfs_attr {
  40         struct list_head node;
  41         char path[PATH_SIZE];
  42         char value[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, const char *subsystem)
  81 {
  82         char *pos;
  83
  84         strlcpy(dev->devpath, devpath, sizeof(dev->devpath));
  85         if (subsystem != NULL)
  86                 strlcpy(dev->subsystem, subsystem, sizeof(dev->subsystem));
  87
  88         /* set kernel name */
  89         pos = strrchr(dev->devpath, '/');
  90         if (pos == NULL)
  91                 return;
  92
  93         strlcpy(dev->kernel_name, &pos[1], sizeof(dev->kernel_name));
  94         dbg("kernel_name='%s'", dev->kernel_name);
  95
  96         /* some devices have '!' in their name, change that to '/' */
  97         pos = dev->kernel_name;
  98         while (pos[0] != '\0') {
  99                 if (pos[0] == '!')
 100                         pos[0] = '/';
 101                 pos++;
 102         }
 103
 104         /* get kernel number */
 105         pos = &dev->kernel_name[strlen(dev->kernel_name)];
 106         while (isdigit(pos[-1]))
 107                 pos--;
 108         strlcpy(dev->kernel_number, pos, sizeof(dev->kernel_number));
 109         dbg("kernel_number='%s'", dev->kernel_number);
 110 }
 111
 112 struct sysfs_device *sysfs_device_get(const char *devpath)
 113 {
 114         char path[PATH_SIZE];
 115         char devpath_real[PATH_SIZE];
 116         struct sysfs_device *dev;
 117         struct sysfs_device *dev_loop;
 118         struct stat statbuf;
 119         char link_path[PATH_SIZE];
 120         char link_target[PATH_SIZE];
 121         int len;
 122         char *pos;
 123
 124         dbg("open '%s'", devpath);
 125         strlcpy(devpath_real, devpath, sizeof(devpath_real));
 126         remove_trailing_chars(devpath_real, '/');
 127
 128         strlcpy(path, sysfs_path, sizeof(path));
 129         strlcat(path, devpath_real, sizeof(path));
 130         if (lstat(path, &statbuf) != 0) {
 131                 dbg("stat '%s' failed: %s", devpath, strerror(errno));
 132                 return NULL;
 133         }
 134
 135         /* if we got a link, resolve it to the real device */
 136         if (S_ISLNK(statbuf.st_mode)) {
 137                 int i;
 138                 int back;
 139
 140                 len = readlink(path, link_target, sizeof(link_target));
 141                 if (len <= 0)
 142                         return NULL;
 143                 link_target[len] = '\0';
 144                 dbg("devpath link '%s' points to '%s'", path, link_target);
 145
 146                 for (back = 0; strncmp(&link_target[back * 3], "../", 3) == 0; back++)
 147                         ;
 148                 dbg("base '%s', tail '%s', back %i", devpath_real, &link_target[back * 3], back);
 149                 for (i = 0; i <= back; i++) {
 150                         pos = strrchr(devpath_real, '/');
 151                         if (pos == NULL)
 152                                 return NULL;
 153                         pos[0] = '\0';
 154                 }
 155                 dbg("after moving back '%s'", devpath_real);
 156                 strlcat(devpath_real, "/", sizeof(devpath_real));
 157                 strlcat(devpath_real, &link_target[back * 3], sizeof(devpath_real));
 158         }
 159
 160         /* look for device in cache */
 161         list_for_each_entry(dev_loop, &dev_list, node) {
 162                 if (strcmp(dev_loop->devpath, devpath_real) == 0) {
 163                         dbg("found in cache '%s'", dev_loop->devpath);
 164                         return dev_loop;
 165                 }
 166         }
 167
 168         /* new device */
 169         dbg("'%s'", devpath_real);
 170         dev = malloc(sizeof(struct sysfs_device));
 171         if (dev == NULL)
 172                 return NULL;
 173         memset(dev, 0x00, sizeof(struct sysfs_device));
 174
 175         sysfs_device_set_values(dev, devpath_real, NULL);
 176
 177         /* get subsystem */
 178         if (strncmp(dev->devpath, "/class/", 7) == 0) {
 179                 strlcpy(dev->subsystem, &dev->devpath[7], sizeof(dev->subsystem));
 180                 pos = strchr(dev->subsystem, '/');
 181                 if (pos != NULL)
 182                         pos[0] = '\0';
 183                 else
 184                         dev->subsystem[0] = '\0';
 185         } else if (strncmp(devpath, "/block/", 7) == 0) {
 186                 strlcpy(dev->subsystem, "block", sizeof(dev->subsystem));
 187         } else if (strncmp(devpath, "/devices/", 9) == 0) {
 188                 /* get subsystem from bus name */
 189                 strlcpy(link_path, sysfs_path, sizeof(link_path));
 190                 strlcat(link_path, dev->devpath, sizeof(link_path));
 191                 strlcat(link_path, "/bus", sizeof(link_path));
 192                 len = readlink(link_path, link_target, sizeof(link_target));
 193                 if (len > 0) {
 194                         link_target[len] = '\0';
 195                         dbg("bus link '%s' points to '%s'", link_path, link_target);
 196                         pos = strrchr(link_target, '/');
 197                         if (pos != NULL)
 198                                 strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
 199                 }
 200
 201                 /* get driver name */
 202                 strlcpy(link_path, sysfs_path, sizeof(link_path));
 203                 strlcat(link_path, dev->devpath, sizeof(link_path));
 204                 strlcat(link_path, "/driver", sizeof(link_path));
 205                 len = readlink(link_path, link_target, sizeof(link_target));
 206                 if (len > 0) {
 207                         link_target[len] = '\0';
 208                         dbg("driver link '%s' points to '%s'", link_path, link_target);
 209                         pos = strrchr(link_target, '/');
 210                         if (pos != NULL)
 211                                 strlcpy(dev->driver, &pos[1], sizeof(dev->driver));
 212                 }
 213         } else if (strncmp(devpath, "/bus/", 5) == 0 && strstr(devpath, "/drivers/")) {
 214                 strlcpy(dev->subsystem, "drivers", sizeof(dev->subsystem));
 215         } else if (strncmp(devpath, "/module/", 8) == 0) {
 216                 strlcpy(dev->subsystem, "module", sizeof(dev->subsystem));
 217         }
 218
 219         dbg("add to cache 'devpath=%s', subsystem='%s', driver='%s'", dev->devpath, dev->subsystem, dev->driver);
 220         list_add(&dev->node, &dev_list);
 221
 222         return dev;
 223 }
 224
 225 struct sysfs_device *sysfs_device_get_parent(struct sysfs_device *dev)
 226 {
 227         char parent_devpath[PATH_SIZE];
 228         char device_link[PATH_SIZE];
 229         char device_link_target[PATH_SIZE];
 230         char *pos;
 231         int i;
 232         int len;
 233         int back;
 234
 235         /* requesting a parent is only valid for devices */
 236         if ((strncmp(dev->devpath, "/devices/", 9) != 0) &&
 237             (strncmp(dev->devpath, "/class/", 7) != 0) &&
 238             (strncmp(dev->devpath, "/block/", 7) != 0))
 239                 return NULL;
 240
 241         strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
 242         dbg("'%s'", parent_devpath);
 243
 244         /* strip last element */
 245         pos = strrchr(parent_devpath, '/');
 246         if (pos == NULL || pos == parent_devpath)
 247                 return NULL;
 248         pos[0] = '\0';
 249
 250         /* are we at the top level */
 251         if (strcmp(parent_devpath, "/devices") == 0) {
 252                 dbg("/devices top level");
 253                 return NULL;
 254         }
 255
 256         /* at the top level we may follow the "device" link */
 257         if (strcmp(parent_devpath, "/block") == 0) {
 258                 dbg("/block top level, look for device link");
 259                 goto device_link;
 260         }
 261
 262         if (strncmp(parent_devpath, "/class", 6) == 0) {
 263                 pos = strrchr(parent_devpath, '/');
 264                 if (pos == &parent_devpath[6] || pos == parent_devpath) {
 265                         dbg("class top level, look for device link");
 266                         goto device_link;
 267                 }
 268         }
 269         return sysfs_device_get(parent_devpath);
 270
 271 device_link:
 272         strlcpy(device_link, sysfs_path, sizeof(device_link));
 273         strlcat(device_link, dev->devpath, sizeof(device_link));
 274         strlcat(device_link, "/device", sizeof(device_link));
 275         len = readlink(device_link, device_link_target, sizeof(device_link_target));
 276         if (len < 0)
 277                 return NULL;
 278         device_link_target[len] = '\0';
 279         dbg("device link '%s' points to '%s'", device_link, device_link_target);
 280
 281         for (back = 0; strncmp(&device_link_target[back * 3], "../", 3) == 0; back++)
 282                 ;
 283         strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
 284         dbg("base='%s', tail='%s', back=%i", parent_devpath, &device_link_target[back * 3], back);
 285         for (i = 0; i < back; i++) {
 286                 pos = strrchr(parent_devpath, '/');
 287                 if (pos == NULL)
 288                         return NULL;
 289                 pos[0] = '\0';
 290         }
 291         dbg("after moving back '%s'", parent_devpath);
 292         strlcat(parent_devpath, "/", sizeof(parent_devpath));
 293         strlcat(parent_devpath, &device_link_target[back * 3], sizeof(parent_devpath));
 294         return sysfs_device_get(parent_devpath);
 295 }
 296
 297 char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
 298 {
 299         char path_full[PATH_SIZE];
 300         const char *path;
 301         char value[NAME_SIZE];
 302         struct sysfs_attr *attr_loop;
 303         struct sysfs_attr *attr;
 304         int fd;
 305         ssize_t size;
 306         size_t sysfs_len;
 307
 308         sysfs_len = strlcpy(path_full, sysfs_path, sizeof(path_full));
 309         path = &path_full[sysfs_len];
 310         strlcat(path_full, devpath, sizeof(path_full));
 311         strlcat(path_full, "/", sizeof(path_full));
 312         strlcat(path_full, attr_name, sizeof(path_full));
 313
 314         /* look for attribute in cache */
 315         list_for_each_entry(attr_loop, &attr_list, node) {
 316                 if (strcmp(attr_loop->path, path) == 0) {
 317                         dbg("found in cache '%s'", attr_loop->path);
 318                         return attr_loop->value;
 319                 }
 320         }
 321
 322         /* read attribute value */
 323         fd = open(path_full, O_RDONLY);
 324         if (fd < 0)
 325                 return NULL;
 326         size = read(fd, value, sizeof(value));
 327         close(fd);
 328         if (size < 0)
 329                 return NULL;
 330         if (size == sizeof(value))
 331                 return NULL;
 332         value[size] = '\0';
 333         remove_trailing_chars(value, '\n');
 334
 335         /* store attribute in cache */
 336         attr = malloc(sizeof(struct sysfs_attr));
 337         if (attr == NULL)
 338                 return NULL;
 339         strlcpy(attr->path, path, sizeof(attr->path));
 340         strlcpy(attr->value, value, sizeof(attr->value));
 341         dbg("add to cache '%s' '%s'", attr->path, attr->value);
 342         list_add(&attr->node, &attr_list);
 343
 344         return attr->value;
 345 }