systemd-stable/udev/udev_sysfs.c

/*
 * Copyright (C) 2005-2008 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, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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, see <http://www.gnu.org/licenses/>.
 */

#include <stdlib.h>
#include <stdio.h>
#include <stddef.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <ctype.h>
#include <errno.h>
#include <sys/stat.h>

#include "udev.h"

/* device cache */
static LIST_HEAD(dev_list);

/* attribute value cache */
static LIST_HEAD(attr_list);

struct sysfs_attr {
	struct list_head node;
	char path[UTIL_PATH_SIZE];
	char *value;			/* points to value_local if value is cached */
	char value_local[UTIL_NAME_SIZE];
};

static int resolve_sys_link(struct udev *udev, char *path, size_t size)
{
	char link_path[UTIL_PATH_SIZE];
	char link_target[UTIL_PATH_SIZE];

	int len;
	int i;
	int back;

	util_strlcpy(link_path, udev_get_sys_path(udev), sizeof(link_path));
	util_strlcat(link_path, path, sizeof(link_path));
	len = readlink(link_path, link_target, sizeof(link_target));
	if (len <= 0)
		return -1;
	link_target[len] = '\0';
	dbg(udev, "path link '%s' points to '%s'\n", path, link_target);

	for (back = 0; strncmp(&link_target[back * 3], "../", 3) == 0; back++)
		;
	dbg(udev, "base '%s', tail '%s', back %i\n", path, &link_target[back * 3], back);
	for (i = 0; i <= back; i++) {
		char *pos = strrchr(path, '/');

		if (pos == NULL)
			return -1;
		pos[0] = '\0';
	}
	dbg(udev, "after moving back '%s'\n", path);
	util_strlcat(path, "/", size);
	util_strlcat(path, &link_target[back * 3], size);
	return 0;
}

int sysfs_init(void)
{
	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 udev *udev,
			     struct sysfs_device *dev, const char *devpath,
			     const char *subsystem, const char *driver)
{
	char *pos;

	util_strlcpy(dev->devpath, devpath, sizeof(dev->devpath));
	if (subsystem != NULL)
		util_strlcpy(dev->subsystem, subsystem, sizeof(dev->subsystem));
	if (driver != NULL)
		util_strlcpy(dev->driver, driver, sizeof(dev->driver));

	/* set kernel name */
	pos = strrchr(dev->devpath, '/');
	if (pos == NULL)
		return;
	util_strlcpy(dev->kernel, &pos[1], sizeof(dev->kernel));
	dbg(udev, "kernel='%s'\n", 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--;
	util_strlcpy(dev->kernel_number, pos, sizeof(dev->kernel_number));
	dbg(udev, "kernel_number='%s'\n", dev->kernel_number);
}

struct sysfs_device *sysfs_device_get(struct udev *udev, const char *devpath)
{
	char path[UTIL_PATH_SIZE];
	char devpath_real[UTIL_PATH_SIZE];
	struct sysfs_device *dev;
	struct sysfs_device *dev_loop;
	struct stat statbuf;
	char link_path[UTIL_PATH_SIZE];
	char link_target[UTIL_PATH_SIZE];
	int len;
	char *pos;

	/* we handle only these devpathes */
	if (devpath != NULL &&
	    strncmp(devpath, "/devices/", 9) != 0 &&
	    strncmp(devpath, "/subsystem/", 11) != 0 &&
	    strncmp(devpath, "/module/", 8) != 0 &&
	    strncmp(devpath, "/bus/", 5) != 0 &&
	    strncmp(devpath, "/class/", 7) != 0 &&
	    strncmp(devpath, "/block/", 7) != 0)
		return NULL;

	dbg(udev, "open '%s'\n", devpath);
	util_strlcpy(devpath_real, devpath, sizeof(devpath_real));
	util_remove_trailing_chars(devpath_real, '/');
	if (devpath[0] == '\0' )
		return NULL;

	/* 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(udev, "found in cache '%s'\n", dev_loop->devpath);
			return dev_loop;
		}
	}

	/* if we got a link, resolve it to the real device */
	util_strlcpy(path, udev_get_sys_path(udev), sizeof(path));
	util_strlcat(path, devpath_real, sizeof(path));
	if (lstat(path, &statbuf) != 0) {
		dbg(udev, "stat '%s' failed: %m\n", path);
		return NULL;
	}
	if (S_ISLNK(statbuf.st_mode)) {
		if (resolve_sys_link(udev, devpath_real, sizeof(devpath_real)) != 0)
			return NULL;

		/* 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(udev, "found in cache '%s'\n", dev_loop->devpath);
				return dev_loop;
			}
		}
	}

	/* it is a new device */
	dbg(udev, "new uncached device '%s'\n", devpath_real);
	dev = malloc(sizeof(struct sysfs_device));
	if (dev == NULL)
		return NULL;
	memset(dev, 0x00, sizeof(struct sysfs_device));

	sysfs_device_set_values(udev, dev, devpath_real, NULL, NULL);

	/* get subsystem name */
	util_strlcpy(link_path, udev_get_sys_path(udev), sizeof(link_path));
	util_strlcat(link_path, dev->devpath, sizeof(link_path));
	util_strlcat(link_path, "/subsystem", sizeof(link_path));
	len = readlink(link_path, link_target, sizeof(link_target));
	if (len > 0) {
		/* get subsystem from "subsystem" link */
		link_target[len] = '\0';
		dbg(udev, "subsystem link '%s' points to '%s'\n", link_path, link_target);
		pos = strrchr(link_target, '/');
		if (pos != NULL)
			util_strlcpy(dev->subsystem, &pos[1], sizeof(dev->subsystem));
	} else if (strstr(dev->devpath, "/drivers/") != NULL) {
		util_strlcpy(dev->subsystem, "drivers", sizeof(dev->subsystem));
	} else if (strncmp(dev->devpath, "/module/", 8) == 0) {
		util_strlcpy(dev->subsystem, "module", sizeof(dev->subsystem));
	} else if (strncmp(dev->devpath, "/subsystem/", 11) == 0) {
		pos = strrchr(dev->devpath, '/');
		if (pos == &dev->devpath[10])
			util_strlcpy(dev->subsystem, "subsystem", sizeof(dev->subsystem));
	} else if (strncmp(dev->devpath, "/class/", 7) == 0) {
		pos = strrchr(dev->devpath, '/');
		if (pos == &dev->devpath[6])
			util_strlcpy(dev->subsystem, "subsystem", sizeof(dev->subsystem));
	} else if (strncmp(dev->devpath, "/bus/", 5) == 0) {
		pos = strrchr(dev->devpath, '/');
		if (pos == &dev->devpath[4])
			util_strlcpy(dev->subsystem, "subsystem", sizeof(dev->subsystem));
	}

	/* get driver name */
	util_strlcpy(link_path, udev_get_sys_path(udev), sizeof(link_path));
	util_strlcat(link_path, dev->devpath, sizeof(link_path));
	util_strlcat(link_path, "/driver", sizeof(link_path));
	len = readlink(link_path, link_target, sizeof(link_target));
	if (len > 0) {
		link_target[len] = '\0';
		dbg(udev, "driver link '%s' points to '%s'\n", link_path, link_target);
		pos = strrchr(link_target, '/');
		if (pos != NULL)
			util_strlcpy(dev->driver, &pos[1], sizeof(dev->driver));
	}

	dbg(udev, "add to cache 'devpath=%s', subsystem='%s', driver='%s'\n", dev->devpath, dev->subsystem, dev->driver);
	list_add(&dev->node, &dev_list);

	return dev;
}

struct sysfs_device *sysfs_device_get_parent(struct udev *udev, struct sysfs_device *dev)
{
	char parent_devpath[UTIL_PATH_SIZE];
	char *pos;

	dbg(udev, "open '%s'\n", dev->devpath);

	/* look if we already know the parent */
	if (dev->parent != NULL)
		return dev->parent;

	util_strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
	dbg(udev, "'%s'\n", parent_devpath);

	/* strip last element */
	pos = strrchr(parent_devpath, '/');
	if (pos == NULL || pos == parent_devpath)
		return NULL;
	pos[0] = '\0';

	if (strncmp(parent_devpath, "/class", 6) == 0) {
		pos = strrchr(parent_devpath, '/');
		if (pos == &parent_devpath[6] || pos == parent_devpath) {
			dbg(udev, "/class top level, look for device link\n");
			goto device_link;
		}
	}
	if (strcmp(parent_devpath, "/block") == 0) {
		dbg(udev, "/block top level, look for device link\n");
		goto device_link;
	}

	/* are we at the top level? */
	pos = strrchr(parent_devpath, '/');
	if (pos == NULL || pos == parent_devpath)
		return NULL;

	/* get parent and remember it */
	dev->parent = sysfs_device_get(udev, parent_devpath);
	return dev->parent;

device_link:
	util_strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
	util_strlcat(parent_devpath, "/device", sizeof(parent_devpath));
	if (resolve_sys_link(udev, parent_devpath, sizeof(parent_devpath)) != 0)
		return NULL;

	/* get parent and remember it */
	dev->parent = sysfs_device_get(udev, parent_devpath);
	return dev->parent;
}

struct sysfs_device *sysfs_device_get_parent_with_subsystem(struct udev *udev, struct sysfs_device *dev, const char *subsystem)
{
	struct sysfs_device *dev_parent;

	dev_parent = sysfs_device_get_parent(udev, dev);
	while (dev_parent != NULL) {
		if (strcmp(dev_parent->subsystem, subsystem) == 0)
			return dev_parent;
		dev_parent = sysfs_device_get_parent(udev, dev_parent);
	}
	return NULL;
}

char *sysfs_attr_get_value(struct udev *udev, const char *devpath, const char *attr_name)
{
	char path_full[UTIL_PATH_SIZE];
	const char *path;
	char value[UTIL_NAME_SIZE];
	struct sysfs_attr *attr_loop;
	struct sysfs_attr *attr;
	struct stat statbuf;
	int fd;
	ssize_t size;
	size_t sysfs_len;

	dbg(udev, "open '%s'/'%s'\n", devpath, attr_name);
	sysfs_len = util_strlcpy(path_full, udev_get_sys_path(udev), sizeof(path_full));
	if(sysfs_len >= sizeof(path_full))
		sysfs_len = sizeof(path_full) - 1;
	path = &path_full[sysfs_len];
	util_strlcat(path_full, devpath, sizeof(path_full));
	util_strlcat(path_full, "/", sizeof(path_full));
	util_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(udev, "found in cache '%s'\n", attr_loop->path);
			return attr_loop->value;
		}
	}

	/* store attribute in cache (also negatives are kept in cache) */
	dbg(udev, "new uncached attribute '%s'\n", path_full);
	attr = malloc(sizeof(struct sysfs_attr));
	if (attr == NULL)
		return NULL;
	memset(attr, 0x00, sizeof(struct sysfs_attr));
	util_strlcpy(attr->path, path, sizeof(attr->path));
	dbg(udev, "add to cache '%s'\n", path_full);
	list_add(&attr->node, &attr_list);

	if (lstat(path_full, &statbuf) != 0) {
		dbg(udev, "stat '%s' failed: %m\n", path_full);
		goto out;
	}

	if (S_ISLNK(statbuf.st_mode)) {
		/* links return the last element of the target path */
		char link_target[UTIL_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(udev, "cache '%s' with link value '%s'\n", path_full, value);
				util_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(udev, "attribute '%s' can not be opened\n", 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';
	util_remove_trailing_chars(value, '\n');
	dbg(udev, "cache '%s' with attribute value '%s'\n", path_full, value);
	util_strlcpy(attr->value_local, value, sizeof(attr->value_local));
	attr->value = attr->value_local;

out:
	return attr->value;
}

int sysfs_lookup_devpath_by_subsys_id(struct udev *udev, char *devpath_full, size_t len, const char *subsystem, const char *id)
{
	size_t sysfs_len;
	char path_full[UTIL_PATH_SIZE];
	char *path;
	struct stat statbuf;

	sysfs_len = util_strlcpy(path_full, udev_get_sys_path(udev), sizeof(path_full));
	path = &path_full[sysfs_len];

	if (strcmp(subsystem, "subsystem") == 0) {
		util_strlcpy(path, "/subsystem/", sizeof(path_full) - sysfs_len);
		util_strlcat(path, id, sizeof(path_full) - sysfs_len);
		if (stat(path_full, &statbuf) == 0)
			goto found;

		util_strlcpy(path, "/bus/", sizeof(path_full) - sysfs_len);
		util_strlcat(path, id, sizeof(path_full) - sysfs_len);
		if (stat(path_full, &statbuf) == 0)
			goto found;
		goto out;

		util_strlcpy(path, "/class/", sizeof(path_full) - sysfs_len);
		util_strlcat(path, id, sizeof(path_full) - sysfs_len);
		if (stat(path_full, &statbuf) == 0)
			goto found;
	}

	if (strcmp(subsystem, "module") == 0) {
		util_strlcpy(path, "/module/", sizeof(path_full) - sysfs_len);
		util_strlcat(path, id, sizeof(path_full) - sysfs_len);
		if (stat(path_full, &statbuf) == 0)
			goto found;
		goto out;
	}

	if (strcmp(subsystem, "drivers") == 0) {
		char subsys[UTIL_NAME_SIZE];
		char *driver;

		util_strlcpy(subsys, id, sizeof(subsys));
		driver = strchr(subsys, ':');
		if (driver != NULL) {
			driver[0] = '\0';
			driver = &driver[1];
			util_strlcpy(path, "/subsystem/", sizeof(path_full) - sysfs_len);
			util_strlcat(path, subsys, sizeof(path_full) - sysfs_len);
			util_strlcat(path, "/drivers/", sizeof(path_full) - sysfs_len);
			util_strlcat(path, driver, sizeof(path_full) - sysfs_len);
			if (stat(path_full, &statbuf) == 0)
				goto found;

			util_strlcpy(path, "/bus/", sizeof(path_full) - sysfs_len);
			util_strlcat(path, subsys, sizeof(path_full) - sysfs_len);
			util_strlcat(path, "/drivers/", sizeof(path_full) - sysfs_len);
			util_strlcat(path, driver, sizeof(path_full) - sysfs_len);
			if (stat(path_full, &statbuf) == 0)
				goto found;
		}
		goto out;
	}

	util_strlcpy(path, "/subsystem/", sizeof(path_full) - sysfs_len);
	util_strlcat(path, subsystem, sizeof(path_full) - sysfs_len);
	util_strlcat(path, "/devices/", sizeof(path_full) - sysfs_len);
	util_strlcat(path, id, sizeof(path_full) - sysfs_len);
	if (stat(path_full, &statbuf) == 0)
		goto found;

	util_strlcpy(path, "/bus/", sizeof(path_full) - sysfs_len);
	util_strlcat(path, subsystem, sizeof(path_full) - sysfs_len);
	util_strlcat(path, "/devices/", sizeof(path_full) - sysfs_len);
	util_strlcat(path, id, sizeof(path_full) - sysfs_len);
	if (stat(path_full, &statbuf) == 0)
		goto found;

	util_strlcpy(path, "/class/", sizeof(path_full) - sysfs_len);
	util_strlcat(path, subsystem, sizeof(path_full) - sysfs_len);
	util_strlcat(path, "/", sizeof(path_full) - sysfs_len);
	util_strlcat(path, id, sizeof(path_full) - sysfs_len);
	if (stat(path_full, &statbuf) == 0)
		goto found;
out:
	return 0;
found:
	if (S_ISLNK(statbuf.st_mode))
		resolve_sys_link(udev, path, sizeof(path_full) - sysfs_len);
	util_strlcpy(devpath_full, path, len);
	return 1;
}