X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=udev_sysfs.c;h=c4cd4ab75dd7146a3c22f3814c350075863b9306;hp=172f0ce1fdd4b3e95999c4f9f5c1ee0043c9bdd4;hb=661a0bea80d129d5df708e36dbaed745c9d8392e;hpb=6ecd4d1e364ea8104c83e36b82d1c23835fb104b

diff --git a/udev_sysfs.c b/udev_sysfs.c
index 172f0ce1f..c4cd4ab75 100644
--- a/udev_sysfs.c
+++ b/udev_sysfs.c
@@ -1,7 +1,5 @@
 /*
- * udev_sysfs.c - sysfs access
- *
- * Copyright (C) 2005 Kay Sievers <kay.sievers@vrfy.org>
+ * 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
@@ -14,7 +12,7 @@
  * 
  *	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.,
- *	675 Mass Ave, Cambridge, MA 02139, USA.
+ *	51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  *
  */
 
@@ -26,6 +24,7 @@
 #include <fcntl.h>
 #include <ctype.h>
 #include <errno.h>
+#include <sys/stat.h>
 
 #include "udev.h"
 
@@ -39,7 +38,8 @@ static LIST_HEAD(attr_list);
 struct sysfs_attr {
 	struct list_head node;
 	char path[PATH_SIZE];
-	char value[NAME_SIZE];
+	char *value;			/* points to value_local if value is cached */
+	char value_local[NAME_SIZE];
 };
 
 int sysfs_init(void)
@@ -52,7 +52,7 @@ int sysfs_init(void)
 		remove_trailing_chars(sysfs_path, '/');
 	} else
 		strlcpy(sysfs_path, "/sys", sizeof(sysfs_path));
-	dbg("sysfs_path='%s'", sysfs_path);
+	dbg("sysfs_path='%s'\n", sysfs_path);
 
 	INIT_LIST_HEAD(&dev_list);
 	INIT_LIST_HEAD(&attr_list);
@@ -77,24 +77,26 @@ void sysfs_cleanup(void)
 	}
 }
 
-void sysfs_device_set_values(struct sysfs_device *dev, const char *devpath, const char *subsystem)
+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_name, &pos[1], sizeof(dev->kernel_name));
-	dbg("kernel_name='%s'", dev->kernel_name);
+	strlcpy(dev->kernel, &pos[1], sizeof(dev->kernel));
+	dbg("kernel='%s'\n", dev->kernel);
 
 	/* some devices have '!' in their name, change that to '/' */
-	pos = dev->kernel_name;
+	pos = dev->kernel;
 	while (pos[0] != '\0') {
 		if (pos[0] == '!')
 			pos[0] = '/';
@@ -102,11 +104,43 @@ void sysfs_device_set_values(struct sysfs_device *dev, const char *devpath, cons
 	}
 
 	/* get kernel number */
-	pos = &dev->kernel_name[strlen(dev->kernel_name)];
+	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);
+	dbg("kernel_number='%s'\n", dev->kernel_number);
+}
+
+int sysfs_resolve_link(char *devpath, size_t size)
+{
+	char link_path[PATH_SIZE];
+	char link_target[PATH_SIZE];
+	int len;
+	int i;
+	int back;
+
+	strlcpy(link_path, sysfs_path, sizeof(link_path));
+	strlcat(link_path, devpath, sizeof(link_path));
+	len = readlink(link_path, link_target, sizeof(link_target));
+	if (len <= 0)
+		return -1;
+	link_target[len] = '\0';
+	dbg("path link '%s' points to '%s'\n", devpath, link_target);
+
+	for (back = 0; strncmp(&link_target[back * 3], "../", 3) == 0; back++)
+		;
+	dbg("base '%s', tail '%s', back %i\n", devpath, &link_target[back * 3], back);
+	for (i = 0; i <= back; i++) {
+		char *pos = strrchr(devpath, '/');
+
+		if (pos == NULL)
+			return -1;
+		pos[0] = '\0';
+	}
+	dbg("after moving back '%s'\n", devpath);
+	strlcat(devpath, "/", size);
+	strlcat(devpath, &link_target[back * 3], size);
+	return 0;
 }
 
 struct sysfs_device *sysfs_device_get(const char *devpath)
@@ -121,114 +155,103 @@ struct sysfs_device *sysfs_device_get(const char *devpath)
 	int len;
 	char *pos;
 
-	dbg("open '%s'", devpath);
+	/* 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("open '%s'\n", devpath);
 	strlcpy(devpath_real, devpath, sizeof(devpath_real));
 	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("found in cache '%s'\n", 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));
+		dbg("stat '%s' failed: %s\n", path, strerror(errno));
 		return NULL;
 	}
-
-	/* if we got a link, resolve it to the real device */
 	if (S_ISLNK(statbuf.st_mode)) {
-		int i;
-		int back;
-
-		len = readlink(path, link_target, sizeof(link_target));
-		if (len <= 0)
+		if (sysfs_resolve_link(devpath_real, sizeof(devpath_real)) != 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));
-	}
 
-	/* look for device in 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;
+		/* 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'\n", dev_loop->devpath);
+				return dev_loop;
+			}
 		}
 	}
 
-	/* new device */
-	dbg("'%s'", devpath_real);
+	/* it is a new device */
+	dbg("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(dev, devpath_real, NULL);
+	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, '/');
+	/* get subsystem name */
+	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) {
+		/* get subsystem from "subsystem" link */
+		link_target[len] = '\0';
+		dbg("subsystem link '%s' points to '%s'\n", link_path, link_target);
+		pos = strrchr(link_target, '/');
 		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, &pos[1], sizeof(dev->subsystem));
+	} else if (strstr(dev->devpath, "/drivers/") != NULL) {
 		strlcpy(dev->subsystem, "drivers", sizeof(dev->subsystem));
 	} else if (strncmp(dev->devpath, "/module/", 8) == 0) {
 		strlcpy(dev->subsystem, "module", sizeof(dev->subsystem));
+	} else if (strncmp(dev->devpath, "/subsystem/", 11) == 0) {
+		pos = strrchr(dev->devpath, '/');
+		if (pos == &dev->devpath[10])
+			strlcpy(dev->subsystem, "subsystem", sizeof(dev->subsystem));
+	} else if (strncmp(dev->devpath, "/class/", 7) == 0) {
+		pos = strrchr(dev->devpath, '/');
+		if (pos == &dev->devpath[6])
+			strlcpy(dev->subsystem, "subsystem", sizeof(dev->subsystem));
+	} else if (strncmp(dev->devpath, "/bus/", 5) == 0) {
+		pos = strrchr(dev->devpath, '/');
+		if (pos == &dev->devpath[4])
+			strlcpy(dev->subsystem, "subsystem", sizeof(dev->subsystem));
 	}
 
-	dbg("add to cache 'devpath=%s', subsystem='%s', driver='%s'", dev->devpath, dev->subsystem, dev->driver);
+	/* 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'\n", link_path, link_target);
+		pos = strrchr(link_target, '/');
+		if (pos != NULL)
+			strlcpy(dev->driver, &pos[1], sizeof(dev->driver));
+	}
+
+	dbg("add to cache 'devpath=%s', subsystem='%s', driver='%s'\n", dev->devpath, dev->subsystem, dev->driver);
 	list_add(&dev->node, &dev_list);
 
 	return dev;
@@ -237,21 +260,16 @@ struct sysfs_device *sysfs_device_get(const char *devpath)
 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;
 
-	/* 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;
+	dbg("open '%s'\n", dev->devpath);
+
+	/* look if we already know the parent */
+	if (dev->parent != NULL)
+		return dev->parent;
 
 	strlcpy(parent_devpath, dev->devpath, sizeof(parent_devpath));
-	dbg("'%s'", parent_devpath);
+	dbg("'%s'\n", parent_devpath);
 
 	/* strip last element */
 	pos = strrchr(parent_devpath, '/');
@@ -259,51 +277,36 @@ struct sysfs_device *sysfs_device_get_parent(struct sysfs_device *dev)
 		return NULL;
 	pos[0] = '\0';
 
-	/* are we at the top level */
-	if (strcmp(parent_devpath, "/devices") == 0) {
-		dbg("/devices top level");
-		return NULL;
-	}
-
-	/* at the top level we may 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");
+			dbg("/class top level, look for device link\n");
 			goto device_link;
 		}
 	}
-	return sysfs_device_get(parent_devpath);
+	if (strcmp(parent_devpath, "/block") == 0) {
+		dbg("/block top level, look for device link\n");
+		goto device_link;
+	}
 
-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)
+	/* are we at the top level? */
+	pos = strrchr(parent_devpath, '/');
+	if (pos == NULL || pos == parent_devpath)
 		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++)
-		;
+	/* get parent and remember it */
+	dev->parent = sysfs_device_get(parent_devpath);
+	return dev->parent;
+
+device_link:
 	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));
-	return sysfs_device_get(parent_devpath);
+	strlcat(parent_devpath, "/device", sizeof(parent_devpath));
+	if (sysfs_resolve_link(parent_devpath, sizeof(parent_devpath)) != 0)
+		return NULL;
+
+	/* 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)
@@ -326,11 +329,15 @@ char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
 	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'\n", devpath, attr_name);
 	sysfs_len = strlcpy(path_full, sysfs_path, sizeof(path_full));
+	if(sysfs_len >= sizeof(path_full))
+		sysfs_len = sizeof(path_full) - 1;
 	path = &path_full[sysfs_len];
 	strlcat(path_full, devpath, sizeof(path_full));
 	strlcat(path_full, "/", sizeof(path_full));
@@ -339,32 +346,164 @@ char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
 	/* 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);
+			dbg("found in cache '%s'\n", attr_loop->path);
 			return attr_loop->value;
 		}
 	}
 
+	/* store attribute in cache (also negatives are kept in cache) */
+	dbg("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));
+	strlcpy(attr->path, path, sizeof(attr->path));
+	dbg("add to cache '%s'\n", path_full);
+	list_add(&attr->node, &attr_list);
+
+	if (lstat(path_full, &statbuf) != 0) {
+		dbg("stat '%s' failed: %s\n", 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'\n", path_full, value);
+				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)
-		return NULL;
+	if (fd < 0) {
+		dbg("attribute '%s' can not be opened\n", path_full);
+		goto out;
+	}
 	size = read(fd, value, sizeof(value));
 	close(fd);
 	if (size < 0)
-		return NULL;
+		goto out;
 	if (size == sizeof(value))
-		return NULL;
+		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'\n", path_full, value);
+	strlcpy(attr->value_local, value, sizeof(attr->value_local));
+	attr->value = attr->value_local;
 
-	/* store attribute in cache */
-	attr = malloc(sizeof(struct sysfs_attr));
-	if (attr == NULL)
-		return NULL;
-	strlcpy(attr->path, path, sizeof(attr->path));
-	strlcpy(attr->value, value, sizeof(attr->value));
-	dbg("add to cache '%s' '%s'", attr->path, attr->value);
-	list_add(&attr->node, &attr_list);
-
+out:
 	return attr->value;
 }
+
+int sysfs_lookup_devpath_by_subsys_id(char *devpath_full, size_t len, const char *subsystem, const char *id)
+{
+	size_t sysfs_len;
+	char path_full[PATH_SIZE];
+	char *path;
+	struct stat statbuf;
+
+	sysfs_len = strlcpy(path_full, sysfs_path, sizeof(path_full));
+	path = &path_full[sysfs_len];
+
+	if (strcmp(subsystem, "subsystem") == 0) {
+		strlcpy(path, "/subsystem/", sizeof(path_full) - sysfs_len);
+		strlcat(path, id, sizeof(path_full) - sysfs_len);
+		if (stat(path_full, &statbuf) == 0)
+			goto found;
+
+		strlcpy(path, "/bus/", sizeof(path_full) - sysfs_len);
+		strlcat(path, id, sizeof(path_full) - sysfs_len);
+		if (stat(path_full, &statbuf) == 0)
+			goto found;
+		goto out;
+
+		strlcpy(path, "/class/", sizeof(path_full) - sysfs_len);
+		strlcat(path, id, sizeof(path_full) - sysfs_len);
+		if (stat(path_full, &statbuf) == 0)
+			goto found;
+	}
+
+	if (strcmp(subsystem, "module") == 0) {
+		strlcpy(path, "/module/", sizeof(path_full) - sysfs_len);
+		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[NAME_SIZE];
+		char *driver;
+
+		strlcpy(subsys, id, sizeof(subsys));
+		driver = strchr(subsys, ':');
+		if (driver != NULL) {
+			driver[0] = '\0';
+			driver = &driver[1];
+			strlcpy(path, "/subsystem/", sizeof(path_full) - sysfs_len);
+			strlcat(path, subsys, sizeof(path_full) - sysfs_len);
+			strlcat(path, "/drivers/", sizeof(path_full) - sysfs_len);
+			strlcat(path, driver, sizeof(path_full) - sysfs_len);
+			if (stat(path_full, &statbuf) == 0)
+				goto found;
+
+			strlcpy(path, "/bus/", sizeof(path_full) - sysfs_len);
+			strlcat(path, subsys, sizeof(path_full) - sysfs_len);
+			strlcat(path, "/drivers/", sizeof(path_full) - sysfs_len);
+			strlcat(path, driver, sizeof(path_full) - sysfs_len);
+			if (stat(path_full, &statbuf) == 0)
+				goto found;
+		}
+		goto out;
+	}
+
+	strlcpy(path, "/subsystem/", sizeof(path_full) - sysfs_len);
+	strlcat(path, subsystem, sizeof(path_full) - sysfs_len);
+	strlcat(path, "/devices/", sizeof(path_full) - sysfs_len);
+	strlcat(path, id, sizeof(path_full) - sysfs_len);
+	if (stat(path_full, &statbuf) == 0)
+		goto found;
+
+	strlcpy(path, "/bus/", sizeof(path_full) - sysfs_len);
+	strlcat(path, subsystem, sizeof(path_full) - sysfs_len);
+	strlcat(path, "/devices/", sizeof(path_full) - sysfs_len);
+	strlcat(path, id, sizeof(path_full) - sysfs_len);
+	if (stat(path_full, &statbuf) == 0)
+		goto found;
+
+	strlcpy(path, "/class/", sizeof(path_full) - sysfs_len);
+	strlcat(path, subsystem, sizeof(path_full) - sysfs_len);
+	strlcat(path, "/", sizeof(path_full) - sysfs_len);
+	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))
+		sysfs_resolve_link(path, sizeof(path_full) - sysfs_len);
+	strlcpy(devpath_full, path, len);
+	return 1;
+}