udev_sysfs.c revision eef5447934a07279bc76f3f65b0302ddea8556ab
/*
* Copyright (C) 2005-2006 Kay Sievers <kay.sievers@vrfy.org>
*
* 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.
*
*/
#include <stdlib.h>
#include <stdio.h>
#include <stddef.h>
#include <unistd.h>
#include <fcntl.h>
#include <ctype.h>
#include <errno.h>
#include <sys/stat.h>
#include "udev.h"
char sysfs_path[PATH_SIZE];
/* device cache */
static LIST_HEAD(dev_list);
/* 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];
};
int sysfs_init(void)
{
const char *env;
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);
INIT_LIST_HEAD(&dev_list);
INIT_LIST_HEAD(&attr_list);
return 0;
}
void sysfs_cleanup(void)
{
struct sysfs_attr *attr_loop;
struct sysfs_attr *attr_temp;
struct sysfs_device *dev_loop;
struct sysfs_device *dev_temp;
list_for_each_entry_safe(attr_loop, attr_temp, &attr_list, node) {
list_del(&attr_loop->node);
free(attr_loop);
}
list_for_each_entry_safe(dev_loop, dev_temp, &dev_list, node) {
list_del(&dev_loop->node);
free(dev_loop);
}
}
void sysfs_device_set_values(struct sysfs_device *dev, const char *devpath,
const char *subsystem, const char *driver)
{
char *pos;
strlcpy(dev->devpath, devpath, sizeof(dev->devpath));
if (subsystem != NULL)
strlcpy(dev->subsystem, subsystem, sizeof(dev->subsystem));
if (driver != NULL)
strlcpy(dev->driver, driver, sizeof(dev->driver));
/* set kernel name */
pos = strrchr(dev->devpath, '/');
if (pos == NULL)
return;
strlcpy(dev->kernel, &pos[1], sizeof(dev->kernel));
dbg("kernel='%s'", dev->kernel);
/* some devices have '!' in their name, change that to '/' */
pos = dev->kernel;
while (pos[0] != '\0') {
if (pos[0] == '!')
pos[0] = '/';
pos++;
}
/* get kernel number */
pos = &dev->kernel[strlen(dev->kernel)];
while (isdigit(pos[-1]))
pos--;
strlcpy(dev->kernel_number, pos, sizeof(dev->kernel_number));
dbg("kernel_number='%s'", dev->kernel_number);
}
struct sysfs_device *sysfs_device_get(const char *devpath)
{
char path[PATH_SIZE];
char devpath_real[PATH_SIZE];
struct sysfs_device *dev;
struct sysfs_device *dev_loop;
struct stat statbuf;
char link_path[PATH_SIZE];
char link_target[PATH_SIZE];
int len;
char *pos;
dbg("open '%s'", devpath);
strlcpy(devpath_real, devpath, sizeof(devpath_real));
remove_trailing_chars(devpath_real, '/');
/* look for device already in cache (we never put an untranslated path in the cache) */
list_for_each_entry(dev_loop, &dev_list, node) {
if (strcmp(dev_loop->devpath, devpath_real) == 0) {
dbg("found in cache '%s'", dev_loop->devpath);
return dev_loop;
}
}
/* if we got a link, resolve it to the real device */
strlcpy(path, sysfs_path, sizeof(path));
strlcat(path, devpath_real, sizeof(path));
if (lstat(path, &statbuf) != 0) {
dbg("stat '%s' failed: %s", path, strerror(errno));
return NULL;
}
if (S_ISLNK(statbuf.st_mode)) {
int i;
int back;
len = readlink(path, link_target, sizeof(link_target));
if (len <= 0)
return NULL;
link_target[len] = '\0';
dbg("devpath link '%s' points to '%s'", path, link_target);
for (back = 0; strncmp(&link_target[back * 3], "../", 3) == 0; back++)
;
dbg("base '%s', tail '%s', back %i", devpath_real, &link_target[back * 3], back);
for (i = 0; i <= back; i++) {
pos = strrchr(devpath_real, '/');
if (pos == NULL)
return NULL;
pos[0] = '\0';
}
dbg("after moving back '%s'", devpath_real);
strlcat(devpath_real, "/", sizeof(devpath_real));
strlcat(devpath_real, &link_target[back * 3], sizeof(devpath_real));
/* now look for device in cache after path translation */
list_for_each_entry(dev_loop, &dev_list, node) {
if (strcmp(dev_loop->devpath, devpath_real) == 0) {
dbg("found in cache '%s'", dev_loop->devpath);
return dev_loop;
}
}
}
/* it is a new device */
dbg("new uncached device '%s'", devpath_real);
dev = malloc(sizeof(struct sysfs_device));
if (dev == NULL)
return NULL;
memset(dev, 0x00, sizeof(struct sysfs_device));
sysfs_device_set_values(dev, devpath_real, NULL, NULL);
/* get subsystem */
if (strncmp(dev->devpath, "/class/", 7) == 0) {
strlcpy(dev->subsystem, &dev->devpath[7], sizeof(dev->subsystem));
pos = strchr(dev->subsystem, '/');
if (pos != NULL)
pos[0] = '\0';
else
dev->subsystem[0] = '\0';
} else if (strncmp(dev->devpath, "/block/", 7) == 0) {
strlcpy(dev->subsystem, "block", sizeof(dev->subsystem));
} else if (strncmp(dev->devpath, "/devices/", 9) == 0) {
/* get subsystem from "bus" link */
strlcpy(link_path, sysfs_path, sizeof(link_path));
strlcat(link_path, dev->devpath, sizeof(link_path));
strlcat(link_path, "/bus", sizeof(link_path));
len = readlink(link_path, link_target, sizeof(link_target));
if (len > 0) {
link_target[len] = '\0';
dbg("bus link '%s' points to '%s'", link_path, link_target);
pos = strrchr(link_target, '/');
if (pos != NULL)
strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
} else {
/* get subsystem from "subsystem" link */
strlcpy(link_path, sysfs_path, sizeof(link_path));
strlcat(link_path, dev->devpath, sizeof(link_path));
strlcat(link_path, "/subsystem", sizeof(link_path));
len = readlink(link_path, link_target, sizeof(link_target));
if (len > 0) {
link_target[len] = '\0';
dbg("subsystem link '%s' points to '%s'", link_path, link_target);
pos = strrchr(link_target, '/');
if (pos != NULL)
strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
}
}
/* get driver name */
strlcpy(link_path, sysfs_path, sizeof(link_path));
strlcat(link_path, dev->devpath, sizeof(link_path));
strlcat(link_path, "/driver", sizeof(link_path));
len = readlink(link_path, link_target, sizeof(link_target));
if (len > 0) {
link_target[len] = '\0';
dbg("driver link '%s' points to '%s'", link_path, link_target);
pos = strrchr(link_target, '/');
if (pos != NULL)
strlcpy(dev->driver, &pos[1], sizeof(dev->driver));
}
} else if (strncmp(dev->devpath, "/bus/", 5) == 0 && strstr(dev->devpath, "/drivers/")) {
strlcpy(dev->subsystem, "drivers", sizeof(dev->subsystem));
} else if (strncmp(dev->devpath, "/module/", 8) == 0) {
strlcpy(dev->subsystem, "module", sizeof(dev->subsystem));
}
dbg("add to cache 'devpath=%s', subsystem='%s', driver='%s'", dev->devpath, dev->subsystem, dev->driver);
list_add(&dev->node, &dev_list);
return dev;
}
struct sysfs_device *sysfs_device_get_parent(struct sysfs_device *dev)
{
char parent_devpath[PATH_SIZE];
char device_link[PATH_SIZE];
char device_link_target[PATH_SIZE];
char *pos;
int i;
int len;
int back;
dbg("open '%s'", dev->devpath);
/* look if we already know the parent */
if (dev->parent != NULL)
return dev->parent;
/* requesting a parent is only valid for devices */
if ((strncmp(dev->devpath, "/devices/", 9) != 0) &&
(strncmp(dev->devpath, "/class/", 7) != 0) &&
(strncmp(dev->devpath, "/block/", 7) != 0))
return NULL;
strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
dbg("'%s'", parent_devpath);
/* strip last element */
pos = strrchr(parent_devpath, '/');
if (pos == NULL || pos == parent_devpath)
return NULL;
pos[0] = '\0';
/* are we at the top level of /devices */
if (strcmp(parent_devpath, "/devices") == 0) {
dbg("/devices top level");
return NULL;
}
/* at the top level of class/block we want to follow the "device" link */
if (strcmp(parent_devpath, "/block") == 0) {
dbg("/block top level, look for device link");
goto device_link;
}
if (strncmp(parent_devpath, "/class", 6) == 0) {
pos = strrchr(parent_devpath, '/');
if (pos == &parent_devpath[6] || pos == parent_devpath) {
dbg("/class top level, look for device link");
goto device_link;
}
}
/* get parent and remember it */
dev->parent = sysfs_device_get(parent_devpath);
return dev->parent;
device_link:
strlcpy(device_link, sysfs_path, sizeof(device_link));
strlcat(device_link, dev->devpath, sizeof(device_link));
strlcat(device_link, "/device", sizeof(device_link));
len = readlink(device_link, device_link_target, sizeof(device_link_target));
if (len < 0)
return NULL;
device_link_target[len] = '\0';
dbg("device link '%s' points to '%s'", device_link, device_link_target);
for (back = 0; strncmp(&device_link_target[back * 3], "../", 3) == 0; back++)
;
strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
dbg("base='%s', tail='%s', back=%i", parent_devpath, &device_link_target[back * 3], back);
for (i = 0; i < back; i++) {
pos = strrchr(parent_devpath, '/');
if (pos == NULL)
return NULL;
pos[0] = '\0';
}
dbg("after moving back '%s'", parent_devpath);
strlcat(parent_devpath, "/", sizeof(parent_devpath));
strlcat(parent_devpath, &device_link_target[back * 3], sizeof(parent_devpath));
/* get parent and remember it */
dev->parent = sysfs_device_get(parent_devpath);
return dev->parent;
}
struct sysfs_device *sysfs_device_get_parent_with_subsystem(struct sysfs_device *dev, const char *subsystem)
{
struct sysfs_device *dev_parent;
dev_parent = sysfs_device_get_parent(dev);
while (dev_parent != NULL) {
if (strcmp(dev_parent->subsystem, subsystem) == 0)
return dev_parent;
dev_parent = sysfs_device_get_parent(dev_parent);
}
return NULL;
}
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];
int len;
const char *pos;
len = readlink(path_full, link_target, sizeof(link_target));
if (len > 0) {
link_target[len] = '\0';
pos = strrchr(link_target, '/');
if (pos != NULL) {
dbg("cache '%s' with link value '%s'", path_full, value);
strlcpy(attr->value_local, &pos[1], sizeof(attr->value_local));
attr->value = attr->value_local;
}
}
} else {
/* 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;
}