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

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Message-ID: <20230119141912.7ad2997a@booty>
Date:   Thu, 19 Jan 2023 14:19:12 +0100
From:   Luca Ceresoli <luca.ceresoli@...tlin.com>
To:     Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...el.com>,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Wolfram Sang <wsa@...nel.org>,
        Matti Vaittinen <Matti.Vaittinen@...rohmeurope.com>,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Peter Rosin <peda@...ntia.se>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Michael Tretter <m.tretter@...gutronix.de>,
        Shawn Tu <shawnx.tu@...el.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Mike Pagano <mpagano@...too.org>,
        Krzysztof Hałasa <khalasa@...p.pl>,
        Marek Vasut <marex@...x.de>
Subject: Re: [PATCH v7 0/7] i2c-atr and FPDLink

Hi Tomi,

On Thu, 19 Jan 2023 14:40:24 +0200
Tomi Valkeinen <tomi.valkeinen@...asonboard.com> wrote:

> On 19/01/2023 10:43, Luca Ceresoli wrote:
> > Hi Andy,
> > 
> > On Wed, 18 Jan 2023 19:43:23 +0200
> > Andy Shevchenko <andriy.shevchenko@...el.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?  
> 
> I thought you had a reason to add them, so I didn't remove them =). I 
> can drop them.

Yes, please drop them.

It's the usual "it looked like a good idea" situation... :)

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