linux-kernel - Re: [PATCH v6 1/8] i2c: core: let adapters be notified of client attach/detach

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Message-ID: <90bc0464-fa49-bd57-5460-d7d2a4bb6b65@ideasonboard.com>
Date:   Sun, 8 Jan 2023 11:24:59 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     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>,
        Luca Ceresoli <luca.ceresoli@...tlin.com>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Matti Vaittinen <Matti.Vaittinen@...rohmeurope.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>,
        Luca Ceresoli <luca@...aceresoli.net>
Subject: Re: [PATCH v6 1/8] i2c: core: let adapters be notified of client
 attach/detach

On 08/01/2023 05:13, Laurent Pinchart wrote:
> Hi Tomi,
> 
> Thank you for the patch.
> 
> On Thu, Jan 05, 2023 at 04:03:00PM +0200, Tomi Valkeinen wrote:
>> From: Luca Ceresoli <luca@...aceresoli.net>
>>
>> An adapter might need to know when a new device is about to be
>> added. This will soon bee needed to implement an "I2C address
>> translator" (ATR for short), a device that propagates I2C transactions
>> with a different slave address (an "alias" address). An ATR driver
>> needs to know when a slave is being added to find a suitable alias and
>> program the device translation map.
>>
>> Add an attach/detach callback pair to allow adapter drivers to be
>> notified of clients being added and removed.
> 
> I've asked in the review of v6 if we could instead use the
> BUS_NOTIFY_ADD_DEVICE and BUS_NOTIFY_DEL_DEVICE bus notifiers. There's
> been a follow up discussion with Andy, but no reply from you AFAICS.
> Have you given this a try ? It's not a mandatory requirement, but if it
> can't be done (or shouldn't be done), I'd like to know why.

Sorry, I meant to mention this in the cover letter, but forgot:

I haven't looked at the bus notifiers yet, but will have a look. I 
wanted to send a new revision due to the large amount of changes already 
done.

  Tomi