linux-kernel - Re: [RFC PATCH v2 1/3] regulator: core: Add regulator_lookup

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Message-ID: <YSZNvSvE2TyGrP7E@pendragon.ideasonboard.com>
Date:   Wed, 25 Aug 2021 17:03:41 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Daniel Scally <djrscally@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        Sakari Ailus <sakari.ailus@....fi>
Subject: Re: [RFC PATCH v2 1/3] regulator: core: Add regulator_lookup_list

On Wed, Aug 25, 2021 at 04:59:36PM +0300, Laurent Pinchart wrote:
> Hello,
> 
> CC'ing Sakari.

With Sakari's correct address.

> On Wed, Aug 25, 2021 at 02:11:39PM +0100, Mark Brown wrote:
> > On Wed, Aug 25, 2021 at 03:26:37PM +0300, Andy Shevchenko wrote:
> > > On Wed, Aug 25, 2021 at 2:30 PM Mark Brown <broonie@...nel.org> wrote:
> > 
> > > > No, what was proposed for regulator was to duplicate all the the DT
> > > > binding code in the regulator framework so it parses fwnodes then have
> > > > an API for encoding fwnodes from C data structures at runtime.  The bit
> > > > where the data gets joined up with the devices isn't the problem, it's
> > > > the duplication and fragility introduced by encoding everything into
> > > > an intermediate representation that has no purpose and passing that
> > > > around which is the problem.
> > 
> > > The whole exercise with swnode is to minimize the driver intrusion and
> > > evolving a unified way for (some) of the device properties. V4L2 won't
> > 
> > The practical implementation for regulators was to duplicate a
> > substantial amount of code in the core in order to give us a less type
> > safe and more indirect way of passing data from onen C file in the
> > kernel to another.  This proposal is a lot better in that it uses the
> > existing init_data and avoids the huge amounts of duplication, it's just
> > not clear from the changelog why it's doing this in a regulator specific
> > manner.
> > 
> > *Please* stop trying to force swnodes in everywhere, take on board the
> > feedback about why the swnode implementation is completely inappropriate
> > for regulators.  I don't understand why you continue to push this so
> > hard.  swnodes and fwnodes are a solution to a specific problem, they're
> > not the answer to every problem out there and having to rehash this
> > continually is getting in the way of actually discussing practical
> > workarounds for these poorly implemented ACPI platforms.
> > 
> > > like what you are suggesting exactly because they don't like the idea
> > > of spreading the board code over the drivers. In some cases it might
> > > even be not so straightforward and easy.
> > 
> > > Laurent, do I understand correctly the v4l2 expectations?
> > 
> > There will be some cases where swnodes make sense, for example where the
> > data is going to be read through the fwnode API since the binding is
> > firmware neutral which I think is the v4l case.  On the other hand
> > having a direct C representation is a very common way of implementing
> > DMI quirk tables, and we have things like the regulator API where
> > there's off the shelf platform data support and we actively don't want
> > to support fwnode.
> 
> From a camera sensor point of view, we want to avoid code duplication.
> Having to look for regulators using OF lookups *and* platform data in
> every single sensor driver is not a good solution. This means that, from
> a camera sensor driver point of view, we want to call regulator_get()
> (or the devm_ version) with a name, without caring about who establishes
> the mapping and how the lookup is performed. I don't care much
> personally if this would be implemented through swnode or a different
> mechanism, as long as the implementation can be centralized.

-- 
Regards,

Laurent Pinchart