linux-kernel - Re: [PATCH] arm64: Kconfig.platforms: Re-organized Broadcom menu

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Date:   Wed, 13 Jul 2022 15:05:23 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Florian Fainelli <f.fainelli@...il.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        SoC Team <soc@...nel.org>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        william.zhang@...adcom.com, anand.gore@...adcom.com,
        Olof Johansson <olof@...om.net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Wei Xu <xuwei5@...ilicon.com>, Andrew Lunn <andrew@...n.ch>,
        Gregory Clement <gregory.clement@...tlin.com>,
        "moderated list:ARM/Mediatek SoC..." 
        <linux-mediatek@...ts.infradead.org>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Matthias Brugger <mbrugger@...e.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        "moderated list:ARM/SAMSUNG EXYNOS ARM ARCHITECTURES" 
        <linux-samsung-soc@...r.kernel.org>,
        Dinh Nguyen <dinguyen@...nel.org>
Subject: Re: [PATCH] arm64: Kconfig.platforms: Re-organized Broadcom menu

On 7/13/22 02:17, Geert Uytterhoeven wrote:
> Hi Krzysztof,
> 
> On Wed, Jul 13, 2022 at 10:40 AM Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org> wrote:
>> On 13/07/2022 10:25, Arnd Bergmann wrote:
>>> On Tue, Jul 12, 2022 at 6:42 PM Florian Fainelli <f.fainelli@...il.com> wrote:
>>>> There are now multiple Broadcom SoCs supported so group them under their
>>>> own menu such that the selection is visually more appealing and we can
>>>> easily add new platforms there in the future. This allows us to move
>>>> ARCH_BRCMSTB back to its siblings.
>>>>
>>>> No functional changes introduced.
>>>>
>>>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>>>> ---
>>>>
>>>> Note this is based on "arm64: bcmbca: add arch bcmbca machine entry"
>>>
>>> Hi Florian,
>>>
>>> So far, we have tried to keep the Kconfig.platforms file rather coarse-grained,
>>> mainly limiting it to company names and high-level families, but avoiding
>>> sub-menus or adding too many sub-families.
>>>
>>> If we add per-vendor submenus, we should probably first decide how we
>>> want to structure this across vendors. I've added maintainers and lists to
>>> Cc for a couple of the ones that are in a similar situation.
>>>
>>> I can see a couple of ways we can do this:
>>>
>>> a) keep the list of platforms as short as possible, combining related
>>>    SoC families from a single vendor wherever possible, but no sub-menus
>>>    (same as today)
>>>
>>> b) Always use sub-menus when there is more than one family, but
>>>     keep relatively coarse platform selection.
>>>
>>> c) Use sub-menus and also move to a more fine-grained SoC
>>>      selection, similar to what we have on 32-bit arm.
>>>
>>> I would not really want to go to c), but a) and b) both make sense to
>>> me as long as do it consistently across all platforms.
>>>
>>> Any other ideas or opinions?
>>
>> Whatever we decide here, the SoC can override in drivers/soc, just like
>> Renesas did. I think Renesas chose option c), but made it in
>> drivers/soc. I would vote to have consistent policy, so if arch/arm64 is
>> a) or b), sub-archs should not redefine it in drivers/soc.
> 
> We did so because of the "only a single symbol in
> arch/arm64/Kconfig.platforms"-policy.

I was not aware of that rule.

It is a bit of a mixed situation with Broadcom SoCs but in essence, each 
Kconfig entry denotes a deeply different SoC architecture at the memory 
subsystem, bus, security or product space that you might not want to 
enable in your kernel. There is definitively sharing of drivers between 
all of the platforms and a lot of cross pollination too but usually 
these are deeply different that different kernel images do make sense.

The itch that I wanted to calm was that ARCH_BRCMSTB was after the other 
Broadcom platforms separated by ARCH_BERLIN. if you prefer a pair of 
KConfig comments to delineate them and flatten the platform selection, 
that works for me, too.
-- 
Florian