linux-kernel - Re: [PATCH RFC] of: Add of_parse_map_iter() helper for nexus node map iteration

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Message-ID: <7h8qfuc4dz.fsf@baylibre.com>
Date: Tue, 25 Nov 2025 11:13:12 -0800
From: Kevin Hilman <khilman@...libre.com>
To: Herve Codina <herve.codina@...tlin.com>
Cc: Rob Herring <robh@...nel.org>, Ulf Hansson <ulf.hansson@...aro.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, devicetree@...r.kernel.org,
 linux-pm@...r.kernel.org, arm-scmi@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] of: Add of_parse_map_iter() helper for nexus node
 map iteration

Herve Codina <herve.codina@...tlin.com> writes:

> Hi Kevin,
>
> On Mon, 24 Nov 2025 17:50:11 -0800
> Kevin Hilman <khilman@...libre.com> wrote:
>
>> >
>> > There's also this in flight for interrupt-map:
>> >
>> > https://lore.kernel.org/all/20251027123601.77216-2-herve.codina@bootlin.com/
>> >
>> > There's probably enough quirks with interrupt-map that we can't use
>> > the same code. Though it may boil down to handling #address-cells and
>> > how the parent is looked up.  
>> 
>> Hmm, I wasn't aware of this, thanks for point it out.  It looks very
>> similar to what i need, except for it's hard-coding the properties as
>> "#interrupt-*".
>> 
>> Seems like this should be generalized to handle the generic nexus-node
>> map. But it also seems to rely on an existing function
>> of_irq_parse_imap_parent() which is also specific to interrupt maps.
>> 
>> That being said, I'm not sure if interrupt-maps are really special, or
>> if they are just a specific case of the nexus node map.  This drivers/of
>> code is breaking my brain, so it's more likely that I simply don't
>> understand enough of it to know how to do this correctly.
>> 
>
> The main difference between interrupt-map [1] and the other nexus node maps
> is that in interrupt-map a child unit address is involved and translated to
> the parent unit address of the matched interrupt-map item.
>
> This child unit address is simply not present in other nexus node maps [2].

Ah, I see.  Thanks for the explanation.  Indeed, that makes it hard to
have common parsing code. :(

Kevin