Re: [RFC PATCH 0/2] Add software node support to regulator framework

From: Mark Brown <broonie@kernel.org>
To: Daniel Scally <djrscally@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Platform Driver <platform-driver-x86@vger.kernel.org>,
	Hans de Goede <hdegoede@redhat.com>,
	Mark Gross <mgross@linux.intel.com>,
	Maximilian Luz <luzmaximilian@gmail.com>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	kieran.bingham@ideasonboard.com
Subject: Re: [RFC PATCH 0/2] Add software node support to regulator framework
Date: Tue, 13 Jul 2021 16:24:54 +0100	[thread overview]
Message-ID: <20210713152454.GC4098@sirena.org.uk> (raw)
In-Reply-To: <e17af9dc-78c0-adb8-1dfb-0698e7a4e394@gmail.com>

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On Tue, Jul 13, 2021 at 12:32:26AM +0100, Daniel Scally wrote:

> I do think it can simplify driver code too; a lot of them aren't written
> to parse platform data to get the init data, as they're just relying on
> reading it from devicetree so in the event that we get more cases like
> this, we need to modify those drivers to look for platform data too. On
> the other hand, even the drivers that don't directly call
> of_get_regulator_init_data() still do that lookup during the
> regulator_of_get_init_data() call in regulator_register(), so the ones
> that do parse platform data for init_data structs will check DT as part
> of regulator_register() anyway. Imitating that seems simpler to me.

The driver code is trivial boilerplate, assuming someone doesn't go and
implement a helper to register stuff separately like I suggested.  The
proposed swnode stuff would involve duplicating the DT parsing code.
This seems like a whole lot of effort for something that provides a
worse result than either of the existing things.

> It also creates some problems to suppress the enumeration of the i2c
> device via ACPI (which we'll have to do in a machine specific fashion,
> because some laptops have this chip with properly configured ACPI and

To be clear I think that's a terrible idea.

> > down to being another data table, I imagine you could write a helper for
> > it, or probably even come up with some generic thing that let you
> > register a platform data/DMI combo independently of the driver to get it
> > out of the driver code (looking more like the existing GPIO code which
> > is already being used in another bit of this quirking).

> The advantage of the GPIO lookups is there's no need to have the pointer
> to the registered devices to register the lookup table; we could imitate
> that, by adding entries to a list with the lookup values being device
> and regulator name (with the init data as the thing that's "looked up")
> and check for those during regulator_register() maybe?

Like I keep saying I think that's a much better approach than trying to
use swnodes, they just seem like a terrible fit for the problem.

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