tools lib api cpu: Introduce cpu.[ch] to obtain cpu related information

E.g.:

 $ ./cpu__get_max_freq
 3200000

It does that, as Kan's patch does, by looking at these files:

  $ cat /sys/devices/system/cpu/online
  0-3
  $ ./sysfs__read_ull
  devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
  /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq=3200000
  $

I.e. find out the first online CPU, then read its cpufreq info.

But do it in tools/lib/api/, so that other tools/ living code can use
it, not just perf.
Based-on-a-patch-by: default avatarKan Liang <kan.liang@intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-915v4cvxqplaub8qco66b9mv@git.kernel.orgSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 2d729f6a
libapi-y += fd/ libapi-y += fd/
libapi-y += fs/ libapi-y += fs/
libapi-y += cpu.o
#include <stdio.h>
#include "cpu.h"
#include "fs/fs.h"
int cpu__get_max_freq(unsigned long long *freq)
{
char entry[PATH_MAX];
int cpu;
if (sysfs__read_int("devices/system/cpu/online", &cpu) < 0)
return -1;
snprintf(entry, sizeof(entry),
"devices/system/cpu/cpu%d/cpufreq/cpuinfo_max_freq", cpu);
return sysfs__read_ull(entry, freq);
}
#ifndef __API_CPU__
#define __API_CPU__
int cpu__get_max_freq(unsigned long long *freq);
#endif /* __API_CPU__ */
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