linux-kernel - Re: [PATCH v5 1/8] i2c: core: let adapters be notified of client attach/detach

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Message-ID: <Y6Azg9GJ/ntUlS+P@smile.fi.intel.com>
Date:   Mon, 19 Dec 2022 11:48:51 +0200
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Luca Ceresoli <luca.ceresoli@...tlin.com>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Tomi Valkeinen <tomi.valkeinen@...asonboard.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>,
        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 v5 1/8] i2c: core: let adapters be notified of client
 attach/detach

On Mon, Dec 19, 2022 at 09:51:43AM +0100, Luca Ceresoli wrote:
> On Sun, 11 Dec 2022 18:55:39 +0200
> Laurent Pinchart <laurent.pinchart@...asonboard.com> wrote:
> > On Thu, Dec 08, 2022 at 12:39:59PM +0200, Tomi Valkeinen wrote:

...

> > This may be a stupid question, but couldn't you instead use the
> > BUS_NOTIFY_ADD_DEVICE and BUS_NOTIFY_DEL_DEVICE bus notifiers ?
> 
> I'm not sure they would be the correct tool for this task. Bus
> notifiers inform about new events on the 'struct bus_type, i.e. any
> event on the global i2c bus type. In the i2c world this means being
> notified about new _adapters_, which is exactly what
> drivers/i2c/i2c-dev.c does.
> 
> Here, however, we need to be informed about new _clients_ being added
> under a specific adapter.

This is for example exactly what ACPI integration in I2C framework does. But...

> I'm not sure whether the bus notifiers can
> inform about new clients in addition of new adapters, but they at least
> seem unable to provide per-adapter notification.

...personally I don't like notifiers, they looks like overkill for this task.

> Does that seem correct?

-- 
With Best Regards,
Andy Shevchenko