Re: [PATCH v2 01/11] perf: add PMU_RANGE_ATTR() helper for use by sw-like pmus

[Cody P Schafer]

On 02/25/2014 12:33 PM, Cody P Schafer wrote:
> On 02/24/2014 07:33 PM, Michael Ellerman wrote:
> > On Fri, 2014-14-02 at 22:02:05 UTC, Cody P Schafer wrote:
> > > Add PMU_RANGE_ATTR() and PMU_RANGE_RESV() (for reserved areas) which
> > > generate functions to extract the relevent bits from
> > > event->attr.config{,1,2} for use by sw-like pmus where the
> > > 'config{,1,2}' values don't map directly to hardware registers.
> > >
> > > Signed-off-by: Cody P Schafer <cody@xxxxxxxxxxxxxxxxxx>
> > > ---
> > >   include/linux/perf_event.h | 17 +++++++++++++++++
> > >   1 file changed, 17 insertions(+)
> > >
> > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> > > index e56b07f..2702e91 100644
> > > --- a/include/linux/perf_event.h
> > > +++ b/include/linux/perf_event.h
> > > @@ -871,4 +871,21 @@ _name##_show(struct device
> > > *dev,                    \
> > >                                       \
> > >   static struct device_attribute format_attr_##_name = __ATTR_RO(_name)
> > >
> > > +#define PMU_RANGE_ATTR(name, attr_var, bit_start, bit_end)        \
> > > +PMU_FORMAT_ATTR(name, #attr_var ":" #bit_start "-" #bit_end);        \
> > > +PMU_RANGE_RESV(name, attr_var, bit_start, bit_end)
> > > +
> > > +#define PMU_RANGE_RESV(name, attr_var, bit_start, bit_end)        \
> > > +static u64 event_get_##name##_max(void)                    \
> > > +{                                    \
> > > +    int bits = (bit_end) - (bit_start) + 1;                \
> > > +    return ((0x1ULL << (bits - 1ULL)) - 1ULL) |            \
> > > +        (0xFULL << (bits - 4ULL));                \
> > > +}                                    \
> > > +static u64 event_get_##name(struct perf_event *event)            \
> > > +{                                    \
> > > +    return (event->attr.attr_var >> (bit_start)) &            \
> > > +        event_get_##name##_max();                \
> > > +}
> >
> > I still don't like the names.
> >
> > EVENT_GETTER_AND_FORMAT()
>
> EVENT_RANGE()
>
> I'd prefer to describe the intended usage rather than what is generated
> both in case we change some of the specifics later, and to provide
> additional information to the developers beyond what a simple code
> reading gives.
>
> > EVENT_RESERVED()
>
> Sure. The PMU_* naming was just based on the PMU_FORMAT_ATTR() naming,
> so I kept it for continuity with the existing API. Maybe
> EVENT_RANGE_RESERVED() would be more appropriate?

Thinking about this a bit more, EVENT_RANGE() and EVENT_RANGE_RESERVED() 
aren't quite ideal either. The "EVENT" name collides with the files we 
put in the event/ dir, which these macros generate files for the format/ 
dir. Maybe:

FORMAT_RANGE() and FORMAT_RANGE_RESERVED()
or
PMU_FORMAT_RANGE(), PMU_FORMAT_RANGE_RESERVED()

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