linux-kernel - Re: [PATCH v2 1/2] irqdomain: support three-cell scheme interrupts

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Message-ID: <CACRpkdZn93oA6Tmi4EaWw9U=TAjEAdqgtK+2Ct_Nf1YUUrurgw@mail.gmail.com>
Date: Tue, 4 Mar 2025 08:31:07 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Yixun Lan <dlan@...too.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, Bartosz Golaszewski <brgl@...ev.pl>, Alex Elder <elder@...cstar.com>, 
	Inochi Amaoto <inochiama@...il.com>, linux-kernel@...r.kernel.org, 
	linux-gpio@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	spacemit@...ts.linux.dev, Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v2 1/2] irqdomain: support three-cell scheme interrupts

On Mon, Mar 3, 2025 at 1:40 PM Yixun Lan <dlan@...too.org> wrote:
> On 19:30 Sun 02 Mar     , Thomas Gleixner wrote:

> > Why is the three cell translation not following the one/two cell scheme
> > and has the parameters at the same place (index 0,1), i.e. adding the
> > extra information at the end? That makes sense to me as the extra cell
> > is obviously not directly related to the interrupt mapping.
>
> I think we currently just following the scheme with gpio cells order
> scheme, which is (index(instance) offset flag..), the index and offset
> are parameters to locate the irq which can easily derive from global
> gpio pin number, so I thought it's more intuitive to group them
> orderly together..

Right, the DT bindings are mainly for human consumption, and the
cells are positioned in left-to-right intuitive order.

If they were only for machines it would be another issue, but it's
people who have to write and maintain these files.

For example, in a library a machine could arrange books by
first letter in the title, then by second letter in the title etc, but
that would be very confusing for humans who expect to find
them in author order.

There are many examples of this in the DT bindings.

Yours,
Linus Walleij