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/*
* Copyright (C) 2005-2006 Kay Sievers <kay.sievers@vrfy.org>
* 2008 Jaroslav Kysela <perex@perex.cz>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation version 2 of the License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*/
static char sysfs_path[PATH_SIZE];
/* attribute value cache */
static LIST_HEAD(attr_list);
struct sysfs_attr {
struct list_head node;
char path[PATH_SIZE];
char *value; /* points to value_local if value is cached */
char value_local[NAME_SIZE];
};
static int sysfs_init(void)
{
const char *env;
char sysfs_test[PATH_SIZE];
INIT_LIST_HEAD(&attr_list);
env = getenv("SYSFS_PATH");
if (env) {
strlcpy(sysfs_path, env, sizeof(sysfs_path));
remove_trailing_chars(sysfs_path, '/');
} else
strlcpy(sysfs_path, "/sys", sizeof(sysfs_path));
dbg("sysfs_path='%s'", sysfs_path);
strlcpy(sysfs_test, sysfs_path, sizeof(sysfs_test));
strlcat(sysfs_test, "/kernel/uevent_seqnum", sizeof(sysfs_test));
if (access(sysfs_test, F_OK)) {
strlcpy(sysfs_test, sysfs_path, sizeof(sysfs_test));
strlcat(sysfs_test, "/kernel/uevent_helper", sizeof(sysfs_test));
if (access(sysfs_test, F_OK)) {
error("sysfs path '%s' is invalid", sysfs_path);
return -errno;
}
}
return 0;
}
static void sysfs_cleanup(void)
{
struct sysfs_attr *attr_loop;
struct sysfs_attr *attr_temp;
list_for_each_entry_safe(attr_loop, attr_temp, &attr_list, node) {
list_del(&attr_loop->node);
free(attr_loop);
}
}
static char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
{
char path_full[PATH_SIZE];
const char *path;
char value[NAME_SIZE];
struct sysfs_attr *attr_loop;
struct sysfs_attr *attr;
struct stat statbuf;
int fd;
ssize_t size;
size_t sysfs_len;
dbg("open '%s'/'%s'", devpath, attr_name);
sysfs_len = strlcpy(path_full, sysfs_path, sizeof(path_full));
path = &path_full[sysfs_len];
strlcat(path_full, devpath, sizeof(path_full));
strlcat(path_full, "/", sizeof(path_full));
strlcat(path_full, attr_name, sizeof(path_full));
/* look for attribute in cache */
list_for_each_entry(attr_loop, &attr_list, node) {
if (strcmp(attr_loop->path, path) == 0) {
dbg("found in cache '%s'", attr_loop->path);
return attr_loop->value;
}
}
/* store attribute in cache (also negatives are kept in cache) */
dbg("new uncached attribute '%s'", path_full);
attr = malloc(sizeof(struct sysfs_attr));
if (attr == NULL)
return NULL;
memset(attr, 0x00, sizeof(struct sysfs_attr));
strlcpy(attr->path, path, sizeof(attr->path));
dbg("add to cache '%s'", path_full);
list_add(&attr->node, &attr_list);
if (lstat(path_full, &statbuf) != 0) {
dbg("stat '%s' failed: %s", path_full, strerror(errno));
goto out;
}
if (S_ISLNK(statbuf.st_mode)) {
/* links return the last element of the target path */
char link_target[PATH_SIZE + 1];
int len;
const char *pos;
len = readlink(path_full, link_target, sizeof(link_target) - 1);
if (len > 0) {
link_target[len] = '\0';
pos = strrchr(link_target, '/');
if (pos != NULL) {
dbg("cache '%s' with link value '%s'", path_full, pos+1);
strlcpy(attr->value_local, &pos[1], sizeof(attr->value_local));
attr->value = attr->value_local;
}
}
goto out;
}
/* skip directories */
if (S_ISDIR(statbuf.st_mode))
goto out;
/* skip non-readable files */
if ((statbuf.st_mode & S_IRUSR) == 0)
goto out;
/* read attribute value */
fd = open(path_full, O_RDONLY);
if (fd < 0) {
dbg("attribute '%s' does not exist", path_full);
goto out;
}
size = read(fd, value, sizeof(value));
close(fd);
if (size < 0)
goto out;
if (size == sizeof(value))
goto out;
/* got a valid value, store and return it */
value[size] = '\0';
remove_trailing_chars(value, '\n');
dbg("cache '%s' with attribute value '%s'", path_full, value);
strlcpy(attr->value_local, value, sizeof(attr->value_local));
attr->value = attr->value_local;
out:
return attr->value;
}
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