tools/power/cpupower/lib/acpi_cppc.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2
   3 #include <stdio.h>
   4 #include <errno.h>
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <sys/types.h>
   8 #include <sys/stat.h>
   9 #include <fcntl.h>
  10 #include <unistd.h>
  11
  12 #include "cpupower_intern.h"
  13 #include "acpi_cppc.h"
  14
  15 /* ACPI CPPC sysfs access ***********************************************/
  16
  17 static int acpi_cppc_read_file(unsigned int cpu, const char *fname,
  18                                char *buf, size_t buflen)
  19 {
  20         char path[SYSFS_PATH_MAX];
  21
  22         snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/acpi_cppc/%s",
  23                  cpu, fname);
  24         return cpupower_read_sysfs(path, buf, buflen);
  25 }
  26
  27 static const char * const acpi_cppc_value_files[] = {
  28         [HIGHEST_PERF] = "highest_perf",
  29         [LOWEST_PERF] = "lowest_perf",
  30         [NOMINAL_PERF] = "nominal_perf",
  31         [LOWEST_NONLINEAR_PERF] = "lowest_nonlinear_perf",
  32         [LOWEST_FREQ] = "lowest_freq",
  33         [NOMINAL_FREQ] = "nominal_freq",
  34         [REFERENCE_PERF] = "reference_perf",
  35         [WRAPAROUND_TIME] = "wraparound_time"
  36 };
  37
  38 unsigned long acpi_cppc_get_data(unsigned int cpu, enum acpi_cppc_value which)
  39 {
  40         unsigned long long value;
  41         unsigned int len;
  42         char linebuf[MAX_LINE_LEN];
  43         char *endp;
  44
  45         if (which >= MAX_CPPC_VALUE_FILES)
  46                 return 0;
  47
  48         len = acpi_cppc_read_file(cpu, acpi_cppc_value_files[which],
  49                                   linebuf, sizeof(linebuf));
  50         if (len == 0)
  51                 return 0;
  52
  53         value = strtoull(linebuf, &endp, 0);
  54
  55         if (endp == linebuf || errno == ERANGE)
  56                 return 0;
  57
  58         return value;
  59 }