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

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Date:   Mon, 13 Feb 2023 09:05:12 +0100
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Randy Dunlap" <rdunlap@...radead.org>,
        linux-kernel@...r.kernel.org
Cc:     "MyungJoo Ham" <myungjoo.ham@...sung.com>,
        "Chanwoo Choi" <cw00.choi@...sung.com>,
        "Donggeun Kim" <dg77.kim@...sung.com>,
        "Marc Zyngier" <maz@...nel.org>,
        "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 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.

      Arnd