samples/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
  25 char *
  26 readsysfs(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
  62 readsys_ret:
  63         close(fd);
  64         return string;
  65 }
  66
  67 int
  68 setsysfs(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);
  98 done:
  99         if (oldvalue)
 100                 free(oldvalue);
 101         return ret;
 102 }