linux-kernel - Re: [PATCH 1/2] dt-bindings: mailbox: add support for referencing controllers solely by node

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Message-ID: <20241219-strum-cheese-89e5e60d22c3@spud>
Date: Thu, 19 Dec 2024 18:58:28 +0000
From: Conor Dooley <conor@...nel.org>
To: Tudor Ambarus <tudor.ambarus@...aro.org>
Cc: Conor Dooley <conor.dooley@...rochip.com>,
	Jassi Brar <jassisinghbrar@...il.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, andre.draszik@...aro.org,
	peter.griffin@...aro.org, kernel-team@...roid.com,
	willmcvicker@...gle.com, daniel.lezcano@...aro.org,
	vincent.guittot@...aro.org, ulf.hansson@...aro.org, arnd@...db.de
Subject: Re: [PATCH 1/2] dt-bindings: mailbox: add support for referencing
 controllers solely by node

On Thu, Dec 19, 2024 at 03:42:11PM +0000, Tudor Ambarus wrote:
> Hi, Conor,
> 
> On 12/19/24 2:11 PM, Conor Dooley wrote:
> >> There are mailbox clients that can discover the mailbox channel ID at
> >> run-time. For such cases passing the channel identifier via DT is
> >> redundant. Add support for referencing controllers solely by node.
> > I don't really get your implementation, why not just allow #mbox-cells = 0?
> > That's what's done for things like fixed frequency clocks that only have
> > a single output.
> 
> Ah, indeed!
> 
> instead of:
> 	of_parse_phandle(dev->of_node, "mbox", 0);
> I can do a:
> 	of_parse_phandle_with_args(dev->of_node, "mboxes",
>                                    "#mbox-cells", 0, &of_args)
> where #mbox-cells = 0;
> 
> Or ... can I pass NULL for cells_name and make the #mbox-cells property
> optional and still keeping its requirement of being at least 1?

I think the mbox-cells = 0 approach is preferred, that property is what
marks it as a mailbox controller after all. Perhaps Rob or Krzysztof can
comment?

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