ldetect/trunk/sysfs_attr.c

/*
 * sysfs_dir.c
 *
 * Directory utility functions for libsysfs
 *
 * Copyright (C) IBM Corp. 2003-2005
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library 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
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */
#include "libsysfs.h"
#include "sysfs.h"

/**
 * sysfs_close_attribute: closes and cleans up attribute
 * @sysattr: attribute to close.
 */
void sysfs_close_attribute(struct sysfs_attribute *sysattr)
{
        if (sysattr) {
                if (sysattr->value)
                        free(sysattr->value);
                free(sysattr);
        }
}

/**
 * alloc_attribute: allocates and initializes attribute structure
 * returns struct sysfs_attribute with success and NULL with error.
 */
static struct sysfs_attribute *alloc_attribute(void)
{
        return (struct sysfs_attribute *)
                        calloc(1, sizeof(struct sysfs_attribute));
}

/**
 * sysfs_open_attribute: creates sysfs_attribute structure
 * @path: path to attribute.
 * returns sysfs_attribute struct with success and NULL with error.
 */
struct sysfs_attribute *sysfs_open_attribute(const char *path)
{
        struct sysfs_attribute *sysattr = NULL;
        struct stat fileinfo;

        if (!path) {
                errno = EINVAL;
                return NULL;
        }
        sysattr = alloc_attribute();
        if (!sysattr) {
                dprintf("Error allocating attribute at %s\n", path);
                return NULL;
        }
        if (sysfs_get_name_from_path(path, sysattr->name,
                                SYSFS_NAME_LEN) != 0) {
                dprintf("Error retrieving attrib name from path: %s\n", path);
                sysfs_close_attribute(sysattr);
                return NULL;
        }
        safestrcpy(sysattr->path, path);
        if ((stat(sysattr->path, &fileinfo)) != 0) {
                dprintf("Stat failed: No such attribute?\n");
                sysattr->method = 0;
                free(sysattr);
                sysattr = NULL;
        } else {
                if (fileinfo.st_mode & S_IRUSR)
                        sysattr->method |= SYSFS_METHOD_SHOW;
                if (fileinfo.st_mode & S_IWUSR)
                        sysattr->method |= SYSFS_METHOD_STORE;
        }

        return sysattr;
}

/**
 * sysfs_read_attribute: reads value from attribute
 * @sysattr: attribute to read
 * returns 0 with success and -1 with error.
 */
int sysfs_read_attribute(struct sysfs_attribute *sysattr)
{
        char *fbuf = NULL;
        char *vbuf = NULL;
        ssize_t length = 0;
        long pgsize = 0;
        int fd;

        if (!sysattr) {
                errno = EINVAL;
                return -1;
        }
        if (!(sysattr->method & SYSFS_METHOD_SHOW)) {
                dprintf("Show method not supported for attribute %s\n",
                        sysattr->path);
                errno = EACCES;
                return -1;
        }
        pgsize = getpagesize();
        fbuf = (char *)calloc(1, pgsize+1);
        if (!fbuf) {
                dprintf("calloc failed\n");
                return -1;
        }
        if ((fd = open(sysattr->path, O_RDONLY)) < 0) {
                dprintf("Error reading attribute %s\n", sysattr->path);
                free(fbuf);
                return -1;
        }
        length = read(fd, fbuf, pgsize);
        if (length < 0) {
                dprintf("Error reading from attribute %s\n", sysattr->path);
                close(fd);
                free(fbuf);
                return -1;
        }
        if (sysattr->len > 0) {
                if ((sysattr->len == length) &&
                                (!(strncmp(sysattr->value, fbuf, length)))) {
                        close(fd);
                        free(fbuf);
                        return 0;
                }
                free(sysattr->value);
        }
        sysattr->len = length;
        close(fd);
        vbuf = (char *)realloc(fbuf, length+1);
        if (!vbuf) {
                dprintf("realloc failed\n");
                free(fbuf);
                return -1;
        }
        sysattr->value = vbuf;

        return 0;
}

/**
 * sysfs_write_attribute: write value to the attribute
 * @sysattr: attribute to write
 * @new_value: value to write
 * @len: length of "new_value"
 * returns 0 with success and -1 with error.
 */
int sysfs_write_attribute(struct sysfs_attribute *sysattr,
                const char *new_value, size_t len)
{
        int fd;
        int length;

        if (!sysattr || !new_value || len == 0) {
                errno = EINVAL;
                return -1;
        }

        if (!(sysattr->method & SYSFS_METHOD_STORE)) {
                dprintf ("Store method not supported for attribute %s\n",
                        sysattr->path);
                errno = EACCES;
                return -1;
        }
        if (sysattr->method & SYSFS_METHOD_SHOW) {
                /*
                 * read attribute again to see if we can get an updated value
                 */
                if ((sysfs_read_attribute(sysattr))) {
                        dprintf("Error reading attribute\n");
                        return -1;
                }
                if ((strncmp(sysattr->value, new_value, sysattr->len)) == 0 &&
                                (len == sysattr->len)) {
                        dprintf("Attr %s already has the requested value %s\n",
                                        sysattr->name, new_value);
                        return 0;
                }
        }
        /*
         * open O_WRONLY since some attributes have no "read" but only
         * "write" permission
         */
        if ((fd = open(sysattr->path, O_WRONLY)) < 0) {
                dprintf("Error reading attribute %s\n", sysattr->path);
                return -1;
        }

        length = write(fd, new_value, len);
        if (length < 0) {
                dprintf("Error writing to the attribute %s - invalid value?\n",
                        sysattr->name);
                close(fd);
                return -1;
        } else if ((unsigned int)length != len) {
                dprintf("Could not write %zd bytes to attribute %s\n",
                                        len, sysattr->name);
                /*
                 * since we could not write user supplied number of bytes,
                 * restore the old value if one available
                 */
                if (sysattr->method & SYSFS_METHOD_SHOW) {
                        length = write(fd, sysattr->value, sysattr->len);
                        close(fd);
                        return -1;
                }
        }

        /*
         * Validate length that has been copied. Alloc appropriate area
         * in sysfs_attribute. Verify first if the attribute supports reading
         * (show method). If it does not, do not bother
         */
        if (sysattr->method & SYSFS_METHOD_SHOW) {
                if (length != sysattr->len) {
                        sysattr->value = (char *)realloc
                                (sysattr->value, length);
                        sysattr->len = length;
                        safestrcpymax(sysattr->value, new_value, length);
                } else {
                        /*"length" of the new value is same as old one */
                        safestrcpymax(sysattr->value, new_value, length);
                }
        }

        close(fd);
        return 0;
}

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