Re: [PATCH v7 0/7] i2c-atr and FPDLink

[Tomi Valkeinen]

On 20/01/2023 18:17, Luca Ceresoli wrote:
> Hi Andy,
>
> On Fri, 20 Jan 2023 18:00:02 +0200
> Andy Shevchenko <andriy.shevchenko@xxxxxxxxx> wrote:
>
> > On Thu, Jan 19, 2023 at 09:43:58AM +0100, Luca Ceresoli wrote:
> > > On Wed, 18 Jan 2023 19:43:23 +0200
> > > Andy Shevchenko <andriy.shevchenko@xxxxxxxxx> wrote:
> > > > On Wed, Jan 18, 2023 at 07:28:20PM +0200, Tomi Valkeinen wrote:
> > > > > On 18/01/2023 18:01, Andy Shevchenko wrote:
> > > > > > On Wed, Jan 18, 2023 at 02:40:24PM +0200, Tomi Valkeinen wrote:
> >
> > ...
> >
> > > > > Can you clarify what you mean here?
> > > > >
> > > > > The i2c_clients are not aware of the i2c-atr. They are normal i2c clients.
> > > > > The FPD-Link drivers are aware of the ATR, as the FPD-Link hardware contains
> > > > > the ATR support.
> > > >
> > > > Can't that hardware be represented as I2C adapter? In such case the ATR specifics
> > > > can be hidden from the client (drivers).
> > > >
> > > > I'm worrying about code duplication and other things that leak into drivers as
> > > > ATR callbacks.
> > >
> > > Which callbacks do you refer to? i2c_atr_ops? I don't think we can do
> > > without the attach/detach_client ones, it's where the driver-specific
> > > implementation is hooked for the generic ATR infra to call it.
> > >
> > > However now I noticed the select/deselect ops are still there. IIRC
> > > they are not used by any driver and in the past the plan was to just
> > > remove them. Tomi, do you think there is a good reason to keep them?
> > >    
> > > > It might be that I didn't get how hw exactly functioning on this
> > > > level and why we need those callbacks.
> > >
> > > As far as "how hw exactly works", in case you haven't seen that, the
> > > best explanation I was able to give is in my ELCE 2019 talk, at minute
> > > ~22. It's a 2-3 minute watch. The slides have pointers to other talks
> > > and discussion.
> >
> > Probably I have missed the URL in the discussion, care to resend?
>
> I hadn't sent any URL :)
>
> Here's the shortcut to go straight to the ATR description:
> https://youtu.be/7hLv6fYAW-E?t=1350
>
> Slides:
> https://elinux.org/images/f/fc/Ceresoli-elce2019-video-serdes-linux.pdf

A small note: the current implementation doesn't match the slides, as 
the adapter is now (at least kind of) in the serializer (the "ideal 
solution" in the slides.

 Tomi