1/*
2 * Copyright (C) 2005-2006 Kay Sievers <kay.sievers@vrfy.org>
3 *	              2008 Jaroslav Kysela <perex@perex.cz>
4 *
5 *	This program is free software; you can redistribute it and/or modify it
6 *	under the terms of the GNU General Public License as published by the
7 *	Free Software Foundation version 2 of the License.
8 *
9 *	This program is distributed in the hope that it will be useful, but
10 *	WITHOUT ANY WARRANTY; without even the implied warranty of
11 *	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12 *	General Public License for more details.
13 *
14 *	You should have received a copy of the GNU General Public License along
15 *	with this program; if not, write to the Free Software Foundation, Inc.,
16 *	51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
17 *
18 */
19
20
21static char sysfs_path[PATH_SIZE];
22
23/* attribute value cache */
24static LIST_HEAD(attr_list);
25struct sysfs_attr {
26	struct list_head node;
27	char path[PATH_SIZE];
28	char *value;			/* points to value_local if value is cached */
29	char value_local[NAME_SIZE];
30};
31
32static int sysfs_init(void)
33{
34	const char *env;
35	char sysfs_test[PATH_SIZE];
36
37	INIT_LIST_HEAD(&attr_list);
38
39	env = getenv("SYSFS_PATH");
40	if (env) {
41		strlcpy(sysfs_path, env, sizeof(sysfs_path));
42		remove_trailing_chars(sysfs_path, '/');
43	} else
44		strlcpy(sysfs_path, "/sys", sizeof(sysfs_path));
45	dbg("sysfs_path='%s'", sysfs_path);
46
47	strlcpy(sysfs_test, sysfs_path, sizeof(sysfs_test));
48	strlcat(sysfs_test, "/kernel/uevent_seqnum", sizeof(sysfs_test));
49	if (access(sysfs_test, F_OK)) {
50		strlcpy(sysfs_test, sysfs_path, sizeof(sysfs_test));
51		strlcat(sysfs_test, "/kernel/uevent_helper", sizeof(sysfs_test));
52		if (access(sysfs_test, F_OK)) {
53			error("sysfs path '%s' is invalid", sysfs_path);
54			return -errno;
55		}
56	}
57
58	return 0;
59}
60
61static void sysfs_cleanup(void)
62{
63	struct sysfs_attr *attr_loop;
64	struct sysfs_attr *attr_temp;
65
66	list_for_each_entry_safe(attr_loop, attr_temp, &attr_list, node) {
67		list_del(&attr_loop->node);
68		free(attr_loop);
69	}
70}
71
72static char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
73{
74	char path_full[PATH_SIZE];
75	const char *path;
76	char value[NAME_SIZE];
77	struct sysfs_attr *attr_loop;
78	struct sysfs_attr *attr;
79	struct stat statbuf;
80	int fd;
81	ssize_t size;
82	size_t sysfs_len;
83
84	dbg("open '%s'/'%s'", devpath, attr_name);
85	sysfs_len = strlcpy(path_full, sysfs_path, sizeof(path_full));
86	path = &path_full[sysfs_len];
87	strlcat(path_full, devpath, sizeof(path_full));
88	strlcat(path_full, "/", sizeof(path_full));
89	strlcat(path_full, attr_name, sizeof(path_full));
90
91	/* look for attribute in cache */
92	list_for_each_entry(attr_loop, &attr_list, node) {
93		if (strcmp(attr_loop->path, path) == 0) {
94			dbg("found in cache '%s'", attr_loop->path);
95			return attr_loop->value;
96		}
97	}
98
99	/* store attribute in cache (also negatives are kept in cache) */
100	dbg("new uncached attribute '%s'", path_full);
101	attr = malloc(sizeof(struct sysfs_attr));
102	if (attr == NULL)
103		return NULL;
104	memset(attr, 0x00, sizeof(struct sysfs_attr));
105	strlcpy(attr->path, path, sizeof(attr->path));
106	dbg("add to cache '%s'", path_full);
107	list_add(&attr->node, &attr_list);
108
109	if (lstat(path_full, &statbuf) != 0) {
110		dbg("stat '%s' failed: %s", path_full, strerror(errno));
111		goto out;
112	}
113
114	if (S_ISLNK(statbuf.st_mode)) {
115		/* links return the last element of the target path */
116		char link_target[PATH_SIZE + 1];
117		int len;
118		const char *pos;
119
120		len = readlink(path_full, link_target, sizeof(link_target) - 1);
121		if (len > 0) {
122			link_target[len] = '\0';
123			pos = strrchr(link_target, '/');
124			if (pos != NULL) {
125				dbg("cache '%s' with link value '%s'", path_full, pos+1);
126				strlcpy(attr->value_local, &pos[1], sizeof(attr->value_local));
127				attr->value = attr->value_local;
128			}
129		}
130		goto out;
131	}
132
133	/* skip directories */
134	if (S_ISDIR(statbuf.st_mode))
135		goto out;
136
137	/* skip non-readable files */
138	if ((statbuf.st_mode & S_IRUSR) == 0)
139		goto out;
140
141	/* read attribute value */
142	fd = open(path_full, O_RDONLY);
143	if (fd < 0) {
144		dbg("attribute '%s' does not exist", path_full);
145		goto out;
146	}
147	size = read(fd, value, sizeof(value));
148	close(fd);
149	if (size < 0)
150		goto out;
151	if (size == sizeof(value))
152		goto out;
153
154	/* got a valid value, store and return it */
155	value[size] = '\0';
156	remove_trailing_chars(value, '\n');
157	dbg("cache '%s' with attribute value '%s'", path_full, value);
158	strlcpy(attr->value_local, value, sizeof(attr->value_local));
159	attr->value = attr->value_local;
160
161out:
162	return attr->value;
163}
164