linux-kernel - Re: [PATCH 2/2] PCI: Drop controller CONFIG

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Date:   Tue, 15 Nov 2022 22:04:09 +0100
From:   Pali Rohár <pali@...nel.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH 2/2] PCI: Drop controller CONFIG_OF dependencies

On Tuesday 15 November 2022 14:53:43 Bjorn Helgaas wrote:
> On Tue, Nov 15, 2022 at 08:31:55PM +0100, Pali Rohár wrote:
> > On Tuesday 15 November 2022 12:07:34 Bjorn Helgaas wrote:
> > > On Tue, Nov 15, 2022 at 04:56:10PM +0100, Geert Uytterhoeven wrote:
> > > > On Tue, Oct 25, 2022 at 9:16 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
> > > > > From: Bjorn Helgaas <bhelgaas@...gle.com>
> > > > >
> > > > > Many drivers depend on OF interfaces, so they won't be functional if
> > > > > CONFIG_OF is not set.  But OF provides stub functions in that case, so drop
> > > > > the OF dependencies so we can at least compile-test the drivers.
> > > 
> > > > > --- a/drivers/pci/controller/Kconfig
> > > > > +++ b/drivers/pci/controller/Kconfig
> > > > > @@ -8,7 +8,6 @@ config PCI_MVEBU
> > > > >         depends on ARCH_MVEBU || ARCH_DOVE || COMPILE_TEST
> > > > >         depends on MVEBU_MBUS
> > > > >         depends on ARM
> > > > > -       depends on OF
> > > > 
> > > > This is exactly why we have the COMPILE_TEST symbol.
> > > > There is no point in bothering all users who configure kernels with
> > > > questions about drivers that won't function anyway due to missing
> > > > dependencies, unless the user explicitly wants to do compile-testing.
> > > > 
> > > > So all of these should become:
> > > > 
> > > >     depends on OF || COMPILE_TEST
> > > 
> > > Oh, yes, thanks for pointing this out, I totally blew it here.  I
> > > dropped this while we figure it out.
> > 
> > I agree too, it really makes sense to not provide pci-mvebu driver to
> > end users without OF - it would not work.
> > 
> > Anyway, it is needed to declare "depends on ARM" for pci-mvebu?
> > Both supported architectures (mvebu and dove) are ARM.
> 
> If you're asking whether "depends on ARM" can be removed for
> PCI_MVEBU, I don't know the answer.  I do see that CONFIG_ARCH_MVEBU
> is mentioned in arch/arm64, which doesn't seem to set CONFIG_ARM.

Ou, you are right. Correct interpretation is "depends on 32-bit mvebu".
And because ARCH_MVEBU means "32-bit mvebu OR 64-bit mvebu" there is
additional "depends on ARM" to filter-out 64-bit mvebu.

So _architecture_ dependency based on intention should be:

(ARCH_MVEBU && ARM) || ARCH_DOVE || COMPILE_TEST

But because there is no 64-bit Dove, it has same meaning as moving ARM
from inner conjunction to outer.

I do not know which syntax is better. So choose what you prefer (current
version or some modification).

> In any event, I would consider a change like that to be a separate
> patch.  Here I just want to focus on CONFIG_OF.
> 
> Bjorn