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kernel/linux-imx6_3.14.28/Documentation/mic/mpssd/sysfs.c 2.19 KB
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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
  ",
  			filename, strerror(errno));
  		return NULL;
  	}
  
  	len = read(fd, value, sizeof(value));
  	if (len < 0) {
  		mpsslog("Failed to read sysfs entry '%s': %s
  ",
  			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
  ",
  			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
  ",
  				filename, strerror(errno));
  		}
  	}
  	close(fd);
  done:
  	if (oldvalue)
  		free(oldvalue);
  	return ret;
  }