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/*
* 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;
}
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