sysfs.c
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/*
* Intel MIC Platform Software Stack (MPSS)
*
* Copyright(c) 2013 Intel Corporation.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License, version 2, as
* published by the Free Software Foundation.
*
* 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.
*
* The full GNU General Public License is included in this distribution in
* the file called "COPYING".
*
* Intel MIC User Space Tools.
*/
#include "mpssd.h"
#define PAGE_SIZE 4096
char *
readsysfs(char *dir, char *entry)
{
char filename[PATH_MAX];
char value[PAGE_SIZE];
char *string = NULL;
int fd;
int len;
if (dir == NULL)
snprintf(filename, PATH_MAX, "%s/%s", MICSYSFSDIR, entry);
else
snprintf(filename, PATH_MAX,
"%s/%s/%s", MICSYSFSDIR, dir, entry);
fd = open(filename, O_RDONLY);
if (fd < 0) {
mpsslog("Failed to open sysfs entry '%s': %s\n",
filename, strerror(errno));
return NULL;
}
len = read(fd, value, sizeof(value));
if (len < 0) {
mpsslog("Failed to read sysfs entry '%s': %s\n",
filename, strerror(errno));
goto readsys_ret;
}
if (len == 0)
goto readsys_ret;
value[len - 1] = '\0';
string = malloc(strlen(value) + 1);
if (string)
strcpy(string, value);
readsys_ret:
close(fd);
return string;
}
int
setsysfs(char *dir, char *entry, char *value)
{
char filename[PATH_MAX];
char *oldvalue;
int fd, ret = 0;
if (dir == NULL)
snprintf(filename, PATH_MAX, "%s/%s", MICSYSFSDIR, entry);
else
snprintf(filename, PATH_MAX, "%s/%s/%s",
MICSYSFSDIR, dir, entry);
oldvalue = readsysfs(dir, entry);
fd = open(filename, O_RDWR);
if (fd < 0) {
ret = errno;
mpsslog("Failed to open sysfs entry '%s': %s\n",
filename, strerror(errno));
goto done;
}
if (!oldvalue || strcmp(value, oldvalue)) {
if (write(fd, value, strlen(value)) < 0) {
ret = errno;
mpsslog("Failed to write new sysfs entry '%s': %s\n",
filename, strerror(errno));
}
}
close(fd);
done:
if (oldvalue)
free(oldvalue);
return ret;
}