samples/mic/mpssd/sysfs.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Intel MIC Platform Software Stack (MPSS)
   4  *
   5  * Copyright(c) 2013 Intel Corporation.
   6  *
   7  * Intel MIC User Space Tools.
   8  */
   9
  10 #include "mpssd.h"
  11
  12 #define PAGE_SIZE 4096
  13
  14 char *
  15 readsysfs(char *dir, char *entry)
  16 {
  17         char filename[PATH_MAX];
  18         char value[PAGE_SIZE];
  19         char *string = NULL;
  20         int fd;
  21         int len;
  22
  23         if (dir == NULL)
  24                 snprintf(filename, PATH_MAX, "%s/%s", MICSYSFSDIR, entry);
  25         else
  26                 snprintf(filename, PATH_MAX,
  27                          "%s/%s/%s", MICSYSFSDIR, dir, entry);
  28
  29         fd = open(filename, O_RDONLY);
  30         if (fd < 0) {
  31                 mpsslog("Failed to open sysfs entry '%s': %s\n",
  32                         filename, strerror(errno));
  33                 return NULL;
  34         }
  35
  36         len = read(fd, value, sizeof(value));
  37         if (len < 0) {
  38                 mpsslog("Failed to read sysfs entry '%s': %s\n",
  39                         filename, strerror(errno));
  40                 goto readsys_ret;
  41         }
  42         if (len == 0)
  43                 goto readsys_ret;
  44
  45         value[len - 1] = '\0';
  46
  47         string = malloc(strlen(value) + 1);
  48         if (string)
  49                 strcpy(string, value);
  50
  51 readsys_ret:
  52         close(fd);
  53         return string;
  54 }
  55
  56 int
  57 setsysfs(char *dir, char *entry, char *value)
  58 {
  59         char filename[PATH_MAX];
  60         char *oldvalue;
  61         int fd, ret = 0;
  62
  63         if (dir == NULL)
  64                 snprintf(filename, PATH_MAX, "%s/%s", MICSYSFSDIR, entry);
  65         else
  66                 snprintf(filename, PATH_MAX, "%s/%s/%s",
  67                          MICSYSFSDIR, dir, entry);
  68
  69         oldvalue = readsysfs(dir, entry);
  70
  71         fd = open(filename, O_RDWR);
  72         if (fd < 0) {
  73                 ret = errno;
  74                 mpsslog("Failed to open sysfs entry '%s': %s\n",
  75                         filename, strerror(errno));
  76                 goto done;
  77         }
  78
  79         if (!oldvalue || strcmp(value, oldvalue)) {
  80                 if (write(fd, value, strlen(value)) < 0) {
  81                         ret = errno;
  82                         mpsslog("Failed to write new sysfs entry '%s': %s\n",
  83                                 filename, strerror(errno));
  84                 }
  85         }
  86         close(fd);
  87 done:
  88         if (oldvalue)
  89                 free(oldvalue);
  90         return ret;
  91 }