linux-kernel - Re: [RFC PATCH 1/6] bus: Extract simple-bus into self-contained driver

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Message-ID: <CAE-0n51f_RQqQgH+FidFiFigY7koZCRZoOtDqQeTGKNsKtBSbQ@mail.gmail.com>
Date: Thu, 9 Jan 2025 16:41:04 -0500
From: Stephen Boyd <swboyd@...omium.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>, Rob Herring <robh@...nel.org>
Cc: Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>, 
	linux-kernel@...r.kernel.org, patches@...ts.linux.dev, 
	devicetree@...r.kernel.org, Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, linux-arm-msm@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, Arnd Bergmann <arnd@...db.de>, 
	Conor Dooley <conor+dt@...nel.org>, Saravana Kannan <saravanak@...gle.com>, 
	Uwe Kleine-König <u.kleine-koenig@...libre.com>
Subject: Re: [RFC PATCH 1/6] bus: Extract simple-bus into self-contained driver

Quoting Konrad Dybcio (2025-01-09 06:02:17)
> On 8.01.2025 11:44 PM, Stephen Boyd wrote:
> > Quoting Rob Herring (2025-01-08 06:11:28)
> >> On Tue, Jan 7, 2025 at 7:28 PM Stephen Boyd <swboyd@...omium.org> wrote:
> >>>
> >>> Extract the simple bus into a self contained driver so that devices are
> >>> still populated when a node has two (or more) compatibles with the least
> >>> specific one being the generic "simple-bus". Allow the driver to be a
> >>> module so that in a fully modular build a driver module for the more
> >>> specific compatible will be loaded first before trying to match this
> >>> driver.
> >>>
> >>> Cc: Rob Herring <robh@...nel.org>
> >>> Cc: Saravana Kannan <saravanak@...gle.com>
> >>> Cc: <devicetree@...r.kernel.org>
> >>> Cc: Arnd Bergmann <arnd@...db.de>
> >>> Cc: "Uwe Kleine-König" <u.kleine-koenig@...libre.com>
> >>> Cc: Bjorn Andersson <andersson@...nel.org>
> >>> Cc: Konrad Dybcio <konradybcio@...nel.org>
> >>> Cc: <linux-arm-msm@...r.kernel.org>
> >>> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> >>> ---
>
> [...]
>
> > Maybe the best approach is to simply avoid all of this and drop the
> > "simple-bus" compatible from the soc node? It introduces an annoying
> > hurdle where you have to enable the new driver that does exactly the
> > same thing as "simple-bus" does so you continue to have a working
> > system, but it avoids the headaches of trying to make the fallback to
> > "simple-bus" work and it would match how new DTs would be written. We
> > could make the driver 'default ARCH_<SOC_VENDOR>' so that it gets built
> > for olddefconfig users too.
>
> I think it even makes logical sense for the /soc node's compatible to
> be.. you know.. the model of the SoC we're modeling
>

Sure. The annoying thing is that we'll have to enable the new kernel
driver to keep things working if we don't have some way to fallback to
how it used to work before. I was trying to do that with this patch but
it's easier to just force folks using new DT to use new kernels so
probably we should just do that.