Re: [patch 23/24] perfmon3: kernel documentation

["stephane eranian" <eranian@googlemail.com>]

Pavel,

On Sun, Oct 19, 2008 at 3:37 PM, Pavel Machek <pavel@suse.cz> wrote:
> Hi!
>
>> +   * int pfm_create(int flags, pfarg_sinfo_t *s);
>> +
>> +      This function creates a perfmon per-thread session.
>> +      The flags parameter is currently unused and must be set to 0.
>> +
>> +      Upon return and if s is not NULL, the kernel return the list
>> of available
>
> returns?
>
pfm_create() returns the file descriptor identifying the session or -1
in case of error + errno set.

>> +      PMC and PMD registers. Tools should not assume, they have access to the
>> +      entire PMU, it may be shared with other kernel subsystems, e.g., on X86
>> +      the NMI watchdog timer.
>
> How can kernel return anything?
>
I assume you are talking about pfarg_sinfo_t?
That structure contains bitmasks. If not NULL , the kernel updates the
structure to reflect the
list of available registers.