[RFC 2/2] perf/core: change errno for sampling event not supported in hardware

[Peter Zijlstra]

On Thu, May 12, 2016 at 11:58:43AM +0530, Vineet Gupta wrote:
> On Thursday 12 May 2016 01:06 AM, Peter Zijlstra wrote:
> > On Mon, May 09, 2016 at 10:53:43PM +0530, Vineet Gupta wrote:
> > 
> >> > Right thats what I feared. But hold on, I don't think we need to change the ABI to
> >> > achieve what we want. Gosh why did I even take that path.
> >> > 
> >> > Currently the errno switch case in perf_evsel__open_strerror() in doesn't handle
> >> > ENOTSUPP. So how about we add that - augmented with the same sample_period !0
> >> > check to barf for lack of sampling support.
> >> > 
> >> > Do you see anything wrong with that ?
> >
> > Should work I think.
> 
> Tried that and doesn't even compile. Reconfirms what Vince said, ENOTSUPP is not
> exposed to userspace (being in include/linux and not include/uapi/linux)

Durr, so what does userspace see?