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    SubjectRe: [PATCH v7 0/7] i2c-atr and FPDLink
    Hi Andy,

    On Wed, 18 Jan 2023 19:43:23 +0200
    Andy Shevchenko <andriy.shevchenko@intel.com> 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:
    > > > > Hi,
    > > > >
    > > > > You can find the v6 from:
    > > > >
    > > > > https://lore.kernel.org/all/20230105140307.272052-1-tomi.valkeinen@ideasonboard.com/
    > > > >
    > > > > Main changes:
    > > > >
    > > > > * i2c-atr: Use bus notifier. This allows us to drop the patch that adds
    > > > > the attach_client/detach_client callbacks. On the downside, it removes
    > > > > the option for error handling if the translation setup fails, and also
    > > > > doesn't provide us the pointer to the i2c_board_info. I belive both
    > > > > are acceptable downsides.
    > > > >
    > > > > * Use fwnode in the fpdlink drivers instead of OF
    > > > >
    > > > > * Addressed all the review comments (I hope)
    > > > >
    > > > > * Lots of cosmetic or minor fixes which I came up while doing the fwnode
    > > > > change
    > > >
    > > > I believe my comments to the first driver applies to the next two, so please
    > > > address them whenever you are agree / it's possible / it makes sense.
    > > >
    > > > About ATR implementation. We have the i2c bus (Linux representation of
    > > > the driver model) and i2c_adapter and i2c_client objects there. Can't we
    > > > have an i2c_client_aliased in similar way and be transparent with users?
    >
    > > 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.

    --
    Luca Ceresoli, Bootlin
    Embedded Linux and Kernel engineering
    https://bootlin.com

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