/[soft]/ldetect/trunk/sysfs_attr.c
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Contents of /ldetect/trunk/sysfs_attr.c

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Revision 1357 - (show annotations) (download)
Tue May 17 09:21:22 2011 UTC (10 years ago) by dmorgan
File MIME type: text/plain
File size: 6058 byte(s)
Import  ldetect
1 /*
2 * sysfs_dir.c
3 *
4 * Directory utility functions for libsysfs
5 *
6 * Copyright (C) IBM Corp. 2003-2005
7 *
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with this library; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21 *
22 */
23 #include "libsysfs.h"
24 #include "sysfs.h"
25
26 /**
27 * sysfs_close_attribute: closes and cleans up attribute
28 * @sysattr: attribute to close.
29 */
30 void sysfs_close_attribute(struct sysfs_attribute *sysattr)
31 {
32 if (sysattr) {
33 if (sysattr->value)
34 free(sysattr->value);
35 free(sysattr);
36 }
37 }
38
39 /**
40 * alloc_attribute: allocates and initializes attribute structure
41 * returns struct sysfs_attribute with success and NULL with error.
42 */
43 static struct sysfs_attribute *alloc_attribute(void)
44 {
45 return (struct sysfs_attribute *)
46 calloc(1, sizeof(struct sysfs_attribute));
47 }
48
49 /**
50 * sysfs_open_attribute: creates sysfs_attribute structure
51 * @path: path to attribute.
52 * returns sysfs_attribute struct with success and NULL with error.
53 */
54 struct sysfs_attribute *sysfs_open_attribute(const char *path)
55 {
56 struct sysfs_attribute *sysattr = NULL;
57 struct stat fileinfo;
58
59 if (!path) {
60 errno = EINVAL;
61 return NULL;
62 }
63 sysattr = alloc_attribute();
64 if (!sysattr) {
65 dprintf("Error allocating attribute at %s\n", path);
66 return NULL;
67 }
68 if (sysfs_get_name_from_path(path, sysattr->name,
69 SYSFS_NAME_LEN) != 0) {
70 dprintf("Error retrieving attrib name from path: %s\n", path);
71 sysfs_close_attribute(sysattr);
72 return NULL;
73 }
74 safestrcpy(sysattr->path, path);
75 if ((stat(sysattr->path, &fileinfo)) != 0) {
76 dprintf("Stat failed: No such attribute?\n");
77 sysattr->method = 0;
78 free(sysattr);
79 sysattr = NULL;
80 } else {
81 if (fileinfo.st_mode & S_IRUSR)
82 sysattr->method |= SYSFS_METHOD_SHOW;
83 if (fileinfo.st_mode & S_IWUSR)
84 sysattr->method |= SYSFS_METHOD_STORE;
85 }
86
87 return sysattr;
88 }
89
90 /**
91 * sysfs_read_attribute: reads value from attribute
92 * @sysattr: attribute to read
93 * returns 0 with success and -1 with error.
94 */
95 int sysfs_read_attribute(struct sysfs_attribute *sysattr)
96 {
97 char *fbuf = NULL;
98 char *vbuf = NULL;
99 ssize_t length = 0;
100 long pgsize = 0;
101 int fd;
102
103 if (!sysattr) {
104 errno = EINVAL;
105 return -1;
106 }
107 if (!(sysattr->method & SYSFS_METHOD_SHOW)) {
108 dprintf("Show method not supported for attribute %s\n",
109 sysattr->path);
110 errno = EACCES;
111 return -1;
112 }
113 pgsize = getpagesize();
114 fbuf = (char *)calloc(1, pgsize+1);
115 if (!fbuf) {
116 dprintf("calloc failed\n");
117 return -1;
118 }
119 if ((fd = open(sysattr->path, O_RDONLY)) < 0) {
120 dprintf("Error reading attribute %s\n", sysattr->path);
121 free(fbuf);
122 return -1;
123 }
124 length = read(fd, fbuf, pgsize);
125 if (length < 0) {
126 dprintf("Error reading from attribute %s\n", sysattr->path);
127 close(fd);
128 free(fbuf);
129 return -1;
130 }
131 if (sysattr->len > 0) {
132 if ((sysattr->len == length) &&
133 (!(strncmp(sysattr->value, fbuf, length)))) {
134 close(fd);
135 free(fbuf);
136 return 0;
137 }
138 free(sysattr->value);
139 }
140 sysattr->len = length;
141 close(fd);
142 vbuf = (char *)realloc(fbuf, length+1);
143 if (!vbuf) {
144 dprintf("realloc failed\n");
145 free(fbuf);
146 return -1;
147 }
148 sysattr->value = vbuf;
149
150 return 0;
151 }
152
153 /**
154 * sysfs_write_attribute: write value to the attribute
155 * @sysattr: attribute to write
156 * @new_value: value to write
157 * @len: length of "new_value"
158 * returns 0 with success and -1 with error.
159 */
160 int sysfs_write_attribute(struct sysfs_attribute *sysattr,
161 const char *new_value, size_t len)
162 {
163 int fd;
164 int length;
165
166 if (!sysattr || !new_value || len == 0) {
167 errno = EINVAL;
168 return -1;
169 }
170
171 if (!(sysattr->method & SYSFS_METHOD_STORE)) {
172 dprintf ("Store method not supported for attribute %s\n",
173 sysattr->path);
174 errno = EACCES;
175 return -1;
176 }
177 if (sysattr->method & SYSFS_METHOD_SHOW) {
178 /*
179 * read attribute again to see if we can get an updated value
180 */
181 if ((sysfs_read_attribute(sysattr))) {
182 dprintf("Error reading attribute\n");
183 return -1;
184 }
185 if ((strncmp(sysattr->value, new_value, sysattr->len)) == 0 &&
186 (len == sysattr->len)) {
187 dprintf("Attr %s already has the requested value %s\n",
188 sysattr->name, new_value);
189 return 0;
190 }
191 }
192 /*
193 * open O_WRONLY since some attributes have no "read" but only
194 * "write" permission
195 */
196 if ((fd = open(sysattr->path, O_WRONLY)) < 0) {
197 dprintf("Error reading attribute %s\n", sysattr->path);
198 return -1;
199 }
200
201 length = write(fd, new_value, len);
202 if (length < 0) {
203 dprintf("Error writing to the attribute %s - invalid value?\n",
204 sysattr->name);
205 close(fd);
206 return -1;
207 } else if ((unsigned int)length != len) {
208 dprintf("Could not write %zd bytes to attribute %s\n",
209 len, sysattr->name);
210 /*
211 * since we could not write user supplied number of bytes,
212 * restore the old value if one available
213 */
214 if (sysattr->method & SYSFS_METHOD_SHOW) {
215 length = write(fd, sysattr->value, sysattr->len);
216 close(fd);
217 return -1;
218 }
219 }
220
221 /*
222 * Validate length that has been copied. Alloc appropriate area
223 * in sysfs_attribute. Verify first if the attribute supports reading
224 * (show method). If it does not, do not bother
225 */
226 if (sysattr->method & SYSFS_METHOD_SHOW) {
227 if (length != sysattr->len) {
228 sysattr->value = (char *)realloc
229 (sysattr->value, length);
230 sysattr->len = length;
231 safestrcpymax(sysattr->value, new_value, length);
232 } else {
233 /*"length" of the new value is same as old one */
234 safestrcpymax(sysattr->value, new_value, length);
235 }
236 }
237
238 close(fd);
239 return 0;
240 }
241

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