linux-kernel - Re: [PATCH] mfd: syscon: Use of_io_request_and

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Message-Id: <900066e4-fd5c-4645-bf04-9c27561516a9@app.fastmail.com>
Date:   Fri, 31 Mar 2023 15:06:00 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Loic Poulain" <loic.poulain@...aro.org>
Cc:     "Lee Jones" <lee@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mfd: syscon: Use of_io_request_and_map() for IO mapping

On Thu, Mar 30, 2023, at 15:22, Loic Poulain wrote:
> On Thu, 30 Mar 2023 at 14:45, Arnd Bergmann <arnd@...db.de> wrote:
>> On Thu, Mar 30, 2023, at 13:42, Lee Jones wrote:
>> > On Mon, 20 Mar 2023, Loic Poulain wrote:
>>
>> Thanks for pinging me. I would indeed expect this to cause
>> problems, as syscon mappings are likely to be used in a way
>> that is not entirely clean, with other devices defining
>> overlapping ranges.
>
> Isn't syscon exactly here to address that collision/overlapping issue?
> From a syscon perspective, it seems to be handled correctly at least
> since the mapping is only setup once, with the first user device (in
> syscon_node_to_regmap). Or are you thinking about non syscon devices
> overlapping the syscon area?

I meant them overlapping with other devices. Ideally this should
not exist, but most likely we have to deal with dtb files where
some other device does overlap with a syscon.

     Arnd