lib/librte_power/power_common.c

   1 /* SPDX-License-Identifier: BSD-3-Clause
   2  * Copyright(c) 2020 Intel Corporation
   3  */
   4
   5 #include <limits.h>
   6 #include <stdio.h>
   7 #include <string.h>
   8
   9 #include "power_common.h"
  10
  11 #define POWER_SYSFILE_SCALING_DRIVER   \
  12                 "/sys/devices/system/cpu/cpu%u/cpufreq/scaling_driver"
  13
  14 int
  15 cpufreq_check_scaling_driver(const char *driver_name)
  16 {
  17         unsigned int lcore_id = 0; /* always check core 0 */
  18         char fullpath[PATH_MAX];
  19         char readbuf[PATH_MAX];
  20         char *s;
  21         FILE *f;
  22
  23         /*
  24          * Check if scaling driver matches what we expect.
  25          */
  26         snprintf(fullpath, sizeof(fullpath), POWER_SYSFILE_SCALING_DRIVER,
  27                         lcore_id);
  28         f = fopen(fullpath, "r");
  29
  30         /* if there's no driver at all, bail out */
  31         if (f == NULL)
  32                 return 0;
  33
  34         s = fgets(readbuf, sizeof(readbuf), f);
  35         /* don't need it any more */
  36         fclose(f);
  37
  38         /* if we can't read it, consider unsupported */
  39         if (s == NULL)
  40                 return 0;
  41
  42         /* does the driver name match? */
  43         if (strncmp(readbuf, driver_name, sizeof(readbuf)) != 0)
  44                 return 0;
  45
  46         /*
  47          * We might have a situation where the driver is supported, but we don't
  48          * have permissions to do frequency scaling. This error should not be
  49          * handled here, so consider the system to support scaling for now.
  50          */
  51         return 1;
  52 }