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

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Date:   Wed, 14 Jul 2021 17:05:01 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Daniel Scally <djrscally@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        kieran.bingham@...asonboard.com
Subject: Re: [RFC PATCH 0/2] Add software node support to regulator framework

On Tue, Jul 13, 2021 at 10:46:29PM +0300, Andy Shevchenko wrote:
> On Tue, Jul 13, 2021 at 9:19 PM Mark Brown <broonie@...nel.org> wrote:

> > Like I said in the other mail fwnode is a nice hack for systems that are
> > using ACPI but have hardware that's doing something totally outside the
> > ACPI model to allow them to reuse work that's been done for DT, it's not
> > a universal solution to the lack of appropriate support for describing
> > modern systems in ACPI.

> In some (I suppose rear) cases it may be used by DT-enabled platforms as well.
> I can imagine the case when you have a system in ROM and only what you
> can do to change DTB there is either use DT overlays (which seems to
> be not working, plenty of gaps there according to a Wiki I saw once)
> or do something in the board files.

DT overlays are pretty extensively deployed, it's just that there's very
few use cases where it's done in the kernel - it tends to be better to
do them in either the firmware or a thin wrapper around the kernel so
that the kernel never has to see an unfixed DT, and we don't have to
try to do fixups super early in the boot on a supposedly generic kernel.
The main kernel use cases are things like FPGAs loading a dynamic image
and matching DT at runtime which is a whole additional ball of fun.

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