linux-kernel - Re: [PATCH 1/2] dt-bindings: i3c: dw: Add property to select IBI ops

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Message-ID: <b4ba5fa7834fdfb1a1e26ff0e01b9bb235de63b5.camel@codeconstruct.com.au>
Date: Wed, 26 Jun 2024 16:18:31 +0800
From: Jeremy Kerr <jk@...econstruct.com.au>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, Aniket
 <aniketmaurya@...gle.com>, Alexandre Belloni
 <alexandre.belloni@...tlin.com>,  Joel Stanley <joel@....id.au>, Billy Tsai
 <billy_tsai@...eedtech.com>, Rob Herring <robh@...nel.org>,  Krzysztof
 Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc: linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: i3c: dw: Add property to select IBI ops

Hi Krysztof,

> > > +  ibi-capable:
> > > +    description: Set to select IBI ops.
> 
> What are IBI ops? Standard form letter:
> 
> You described the desired Linux feature or behavior, not the actual
> hardware.

In this case it is the actual hardware; my understanding is that the
gateware IP can be configured to support in-band-interrupts or not,
before being baked-in to hardware.

> > Wouldn't the compatible string select whether the hardware instance
> > supports IBI or not?
> > 
> > I'd imagine that each specific synthesis of the DW IP would imply
> > corresponding hardware settings, and so would warrant its own
> > compatible
> > value.
> > 
> > Maybe one for the DT folks: would this work better as individual
> > properties? Is there a policy here?
> 
> Usually if feature is specific to given hardware, e.g. always capable
> of foobar, then it can be deduced from compatible, so no need for new
> property.

Sounds good.

Aniket: the hardware you're dealing with there may need a new, specific
compatible property, which will dictate whether we enable IBIs in the
driver.

For cases where no other special behaviour is required, we can
represent this just as an entry in the OF match table.

Cheers,


Jeremy