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

From: Luca Ceresoli <luca.ceresoli@bootlin.com>
To: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Cc: "Andy Shevchenko" <andriy.shevchenko@intel.com>,
	linux-media@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org,
	"Rob Herring" <robh+dt@kernel.org>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Wolfram Sang" <wsa@kernel.org>,
	"Matti Vaittinen" <Matti.Vaittinen@fi.rohmeurope.com>,
	"Laurent Pinchart" <laurent.pinchart+renesas@ideasonboard.com>,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"Peter Rosin" <peda@axentia.se>,
	"Liam Girdwood" <lgirdwood@gmail.com>,
	"Mark Brown" <broonie@kernel.org>,
	"Sakari Ailus" <sakari.ailus@linux.intel.com>,
	"Michael Tretter" <m.tretter@pengutronix.de>,
	"Shawn Tu" <shawnx.tu@intel.com>,
	"Hans Verkuil" <hverkuil@xs4all.nl>,
	"Mike Pagano" <mpagano@gentoo.org>,
	"Krzysztof Hałasa" <khalasa@piap.pl>,
	"Marek Vasut" <marex@denx.de>
Subject: Re: [PATCH v7 0/7] i2c-atr and FPDLink
Date: Thu, 19 Jan 2023 14:19:12 +0100	[thread overview]
Message-ID: <20230119141912.7ad2997a@booty> (raw)
In-Reply-To: <024c8127-5109-3ea5-efa0-8c0a8763e8b3@ideasonboard.com>

Hi Tomi,

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