1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
|
/*
* 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];
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_helper", sizeof(sysfs_test));
if (access(sysfs_test, F_OK)) {
error("sysfs path '%s' is invalid\n", sysfs_path);
return -errno;
}
INIT_LIST_HEAD(&attr_list);
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];
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, 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;
}
|
