hwpmc: Always set pmc_cpuid to something

[freqlabs]

Summary

pmc_cpuid was uninitialized for most AMD processor families. We still can populate this string for unimplemented families.

Also removed an extra call to sysctlbyname in libpmc, added a CPUID_TO_STEPPING macro, and converted existing code to use it. I can commit these changes separately, if preferable.

[freqlabs]

lib/libpmc/libpmc_pmu_util.c

172

Ah this can be removed and NULL passed to sysctlbyname instead, too.

[freqlabs]

lib/libpmc/libpmc_pmu_util.c

172

No it should be initialized to the size of the buffer instead.

[freqlabs]

lib/libpmc/libpmc_pmu_util.c

178

This should probably be a strlcpy while I'm making changes here.

[mav]

Looks good to me.

Generally it is not recommended to mix unrelated changes, but too small granularity create too much noise and also is not great, so best is somewhere in the middle. In this case libpmc part looks unrelated and could be committed separately.

[mav]

lib/libpmc/libpmc_pmu_util.c

172

Right.

178

Yes, would not harm, considering it is passed as an argument to the library function,