Re: [RFC PATCH v2 1/3] regulator: core: Add regulator_lookup_list

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hello,

CC'ing Sakari.

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@kernel.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