linux-kernel - Re: [PATCH 0/3] IRQ_DOMAIN: remove all "depends on", use only "select"

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Date:   Tue, 28 Feb 2023 19:29:20 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Donggeun Kim <dg77.kim@...sung.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Peter Rosin <peda@...ntia.se>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Rob Herring <robh@...nel.org>,
        Eddie Huang <eddie.huang@...iatek.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        linux-rtc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 0/3] IRQ_DOMAIN: remove all "depends on", use only "select"

On Thu, 23 Feb 2023 18:37:01 +0000,
Randy Dunlap <rdunlap@...radead.org> wrote:
> 
> Hi Marc,
> 
> On 2/14/23 11:56, Marc Zyngier wrote:
> > On Tue, 14 Feb 2023 18:30:54 +0000,
> > Randy Dunlap <rdunlap@...radead.org> wrote:
> >>
> >>
> >>
> >> On 2/13/23 00:05, Arnd Bergmann wrote:
> >>> On Mon, Feb 13, 2023, at 05:15, Randy Dunlap wrote:
> >>>> IRQ_DOMAIN is a hidden (not user visible) symbol. Users cannot set
> >>>> it directly thru "make *config", so drivers should select it instead
> >>>> of depending on it if they need it.
> >>>> Relying on it being set for a dependency is risky.
> >>>>
> >>>> Consistently using "select" or "depends on" can also help reduce
> >>>> Kconfig circular dependency issues.
> >>>>
> >>>> IRQ_DOMAIN is selected 109 times and is depended on 3 times in
> >>>> current linux-next. Eliminate the uses of "depends on" by
> >>>> converting them to "select".
> >>>>
> >>>>  [PATCH 1/3] extcon: max8997: select IRQ_DOMAIN instead of depending on it
> >>>>  [PATCH 2/3] of: OF_IRQ: select IRQ_DOMAIN instead of depending on it
> >>>>  [PATCH 3/3] rtc: mt6397: select IRQ_DOMAIN instead of depending on it
> >>>
> >>> From a Kconfig perspective, your reasoning makes a lot of sense.
> >>>
> >>> Looking at the bigger picture, I wonder if we should just remove the
> >>> option and make it unconditional. It is enabled in ever architecture
> >>> defconfig other than alpha and sparc, and it's selected by a lot of
> >>> very common options such as I2C,  GENERIC_MSI_IRQ, GENERIC_IRQ_CHIP,
> >>> and PCI_HOST_GENERIC. Enabling the option on Alpha grows the kernel
> >>> image from 9010KB to 9023KB, or on m68k Coldfire from 3346KB to
> >>> 3351KB.
> >>
> >> Marc, what do you think about this suggestion?
> > 
> > Seems sensible enough to me.
> > 
> > I'd also get rid of the IRQ_DOMAIN_HIERARCHY option, which is used by
> > a ton of things. Architectures that are not using it are either dead,
> > or at least terminally comatose.
> > 
> > I'm half-tempted to put the following patch into -next. Maybe after
> > -rc1 though. And then the option can go as well.
> > 
> > 	M.
> 
> What is this patch based on?  It doesn't apply cleanly to current linux-next.

Not very surprising, I usually base my stuff on a stable rc tag. But
in this instance, it may have been based on whatever was in my sandbox
at that point in time, and subsequently discarded.

> I made a similar patch (to linux-next) that drops the IRQ_DOMAIN_HIERARCHY
> option and converts its dependent code to always on.
> It has been built (multiple randconfigs) on all ARCHes (except hexagon),
> both 32-bit and 64-bit where applicable (not that it should matter here).
> 
> But yes, let's plan to get one of these patches in soon (after -rc1).

Please send it based on -rc1 once it is out, and I'll be happy to
stick that in -next for further simmering.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.