[PATCHv2 08/11] arm: arch_timer: add arch_counter_set_user_access

[Will Deacon]

On Fri, Jan 11, 2013 at 02:54:52PM +0000, Mark Rutland wrote:
> On Fri, Jan 11, 2013 at 01:40:22PM +0000, Santosh Shilimkar wrote:
> > So how do you expect platform to enabled the user-space access in case
> > they want to access it for some cases.
> 
> Unlike AArch64, at the moment we don't have the infrastructure to map this for
> userspace accesses, so it isn't much of a problem.
> 
> If in future we wish to map it on 32bit platforms, the arm implementation of
> arch_counter_set_user_access can be modified to allow userspace access to
> specific registers, and additional code would be required to actually map it
> into the user address space, etc.

I'd also add that it's not up to a platform to decide whether to expose
this to userspace: it needs to be an architecture-wide decision. Otherwise,
userspace becomes SoC-specific, which is a complete disaster.

So, if userspace people want these available, they need to convince us to
flip the switch. In the meantime, it should default to off so that if/when
we do enable it we can do it in a sane manner for ARM (perhaps via the
vectors page).

Will