LXR linux/Documentation/mic/mpssd/sysfs.c

   1/*
   2 * Intel MIC Platform Software Stack (MPSS)
   3 *
   4 * Copyright(c) 2013 Intel Corporation.
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License, version 2, as
   8 * published by the Free Software Foundation.
   9 *
  10 * This program is distributed in the hope that it will be useful, but
  11 * WITHOUT ANY WARRANTY; without even the implied warranty of
  12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  13 * General Public License for more details.
  14 *
  15 * The full GNU General Public License is included in this distribution in
  16 * the file called "COPYING".
  17 *
  18 * Intel MIC User Space Tools.
  19 */
  20
  21#include "mpssd.h"
  22
  23#define PAGE_SIZE 4096
  24
  25char *
  26readsysfs(char *dir, char *entry)
  27{
  28        char filename[PATH_MAX];
  29        char value[PAGE_SIZE];
  30        char *string = NULL;
  31        int fd;
  32        int len;
  33
  34        if (dir == NULL)
  35                snprintf(filename, PATH_MAX, "%s/%s", MICSYSFSDIR, entry);
  36        else
  37                snprintf(filename, PATH_MAX,
  38                         "%s/%s/%s", MICSYSFSDIR, dir, entry);
  39
  40        fd = open(filename, O_RDONLY);
  41        if (fd < 0) {
  42                mpsslog("Failed to open sysfs entry '%s': %s\n",
  43                        filename, strerror(errno));
  44                return NULL;
  45        }
  46
  47        len = read(fd, value, sizeof(value));
  48        if (len < 0) {
  49                mpsslog("Failed to read sysfs entry '%s': %s\n",
  50                        filename, strerror(errno));
  51                goto readsys_ret;
  52        }
  53        if (len == 0)
  54                goto readsys_ret;
  55
  56        value[len - 1] = '\0';
  57
  58        string = malloc(strlen(value) + 1);
  59        if (string)
  60                strcpy(string, value);
  61
  62readsys_ret:
  63        close(fd);
  64        return string;
  65}
  66
  67int
  68setsysfs(char *dir, char *entry, char *value)
  69{
  70        char filename[PATH_MAX];
  71        char *oldvalue;
  72        int fd, ret = 0;
  73
  74        if (dir == NULL)
  75                snprintf(filename, PATH_MAX, "%s/%s", MICSYSFSDIR, entry);
  76        else
  77                snprintf(filename, PATH_MAX, "%s/%s/%s",
  78                         MICSYSFSDIR, dir, entry);
  79
  80        oldvalue = readsysfs(dir, entry);
  81
  82        fd = open(filename, O_RDWR);
  83        if (fd < 0) {
  84                ret = errno;
  85                mpsslog("Failed to open sysfs entry '%s': %s\n",
  86                        filename, strerror(errno));
  87                goto done;
  88        }
  89
  90        if (!oldvalue || strcmp(value, oldvalue)) {
  91                if (write(fd, value, strlen(value)) < 0) {
  92                        ret = errno;
  93                        mpsslog("Failed to write new sysfs entry '%s': %s\n",
  94                                filename, strerror(errno));
  95                }
  96        }
  97        close(fd);
  98done:
  99        if (oldvalue)
 100                free(oldvalue);
 101        return ret;
 102}
 103