Re: Suggestion - Configurable Source Clock Type for Line Event Timestamping

[Kent Gibson <warthog618@gmail.com>]

On Mon, Oct 12, 2020 at 03:39:21PM +0200, Bartosz Golaszewski wrote:
> On Mon, Oct 12, 2020 at 1:01 PM Jack Winch <sunt.un.morcov@gmail.com> wrote:
> >
> 
> [snip]
> 
> >
> > > We still haven't released uAPI v2 so I'm open to some last-minute
> > > changes if they make sense (as you explained in the other email about
> > > in-kernel timestamping) and are posted soon (before rc3-rc4). I'd like
> > > to hear Arnd's opinion on this first though.
> >
> >
> > What's the timescales for this?  As I would be doing this in a
> > personal capacity, I will likely have to look at this over a couple of
> > weeks.  I would also be limited to testing on an ARMv8 platform, as I
> > currently have limited access to hardware.
> >
> 
> It would be 3-4 weeks from now.
> 
> In terms of effort: it doesn't look too complicated. It looks like we
> need to add a new flag to the uAPI:
> GPIO_V2_LINE_FLAG_EDGE_CLOCK_REALTIME which would make the edge
> detector use the real-time clock. I wouldn't stress too much about the
> performance of obtaining the timestamp - it's probably negligible
> compared to passing the event struct over to user-space.
> 
> Kent does the above look right?
> 

Could we make that GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME, as it
controls the source of the timestamp in struct gpio_v2_line_event?

Otherwise I don't see any problem with it, and I can have a patch out in
a day or two.

Cheers,
Kent.