linux-kernel - Re: [PATCH v2 3/4] ASoC: dt-bindings: fsl-sai: allow only one dma-names

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Date: Fri, 1 Mar 2024 11:46:20 -0500
From: Frank Li <Frank.li@....com>
To: Conor Dooley <conor@...nel.org>
Cc: Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Shengjiu Wang <shengjiu.wang@....com>, linux-sound@...r.kernel.org,
	devicetree@...r.kernel.org, imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] ASoC: dt-bindings: fsl-sai: allow only one
 dma-names

On Fri, Mar 01, 2024 at 04:05:25PM +0000, Conor Dooley wrote:
> On Thu, Feb 29, 2024 at 02:38:24PM -0500, Frank Li wrote:
> > On Thu, Feb 29, 2024 at 06:57:29PM +0000, Conor Dooley wrote:
> > > On Thu, Feb 29, 2024 at 06:55:58PM +0000, Conor Dooley wrote:
> > > > On Tue, Feb 27, 2024 at 03:54:11PM -0500, Frank Li wrote:
> > > > > Some sai only connect one direction. So allow only "rx" or "tx" for
> > > > > dma-names.
> > > > 
> > > > Which sai? Can you restrict this per compatible please, so that someone
> > > > cannot add 2 dmas for ones where only the tx is supported.
> > > > 
> > > > |  dmas:
> > > > |    minItems: 1
> > > > |    items:
> > > > |      - description: DMA controller phandle and request line for RX
> > > > |      - description: DMA controller phandle and request line for TX
> > > > 
> > > > The binding already allows only one, but it documents that the first dma
> > > > is always the RX dma, and that doesn't change with this patch..
> > > 
> > > I said "doesn't change" - but I don't think you can change this
> > > trivially, as something could rely on the first dma being the rx one.
> > > You'd have to check that there is nothing using these using indices
> > > rather than names before making any changes here.
> > 
> > Linux driver and dts with tx only work well. Only issue is dtb_check will
> > report error. I want to eliminate these DTB_CHECK warning.
> 
> Linux is not the only user of these bindings, citing linux as your
> evidence here is only sufficient if no other users exist. Do they?

But, 'dmas' should be common property for all these bindings? I don't think
they use 'descriptions:' property, which should guide dts writer to write
dts file. actually words 'DMA controller phandle and request line' just
nonsense words. let 'regs', it'd better descript at 'reg-names' instead
of 'regs' if reg-names exist. Only meansful words is "RX" and "TX", which
already show at "dma-names".

> 
> > And it also reasonable, only rx or tx for a special SAI.
> > 
> > Can we remove 'description'? dmas should already descripted at common place
> > and 'RX' and 'TX' are listed at 'dma-names'
> 
> Removing the description has the same problem. The existing binding has
> set a fixed order that you now want to make flexible.

Actually original set minItems: is 1, which means allow 1 channel. but
set items to force two channel. 

Does it work

oneOf:
  items: 
  	- description: TX
	- description: RX
  items:
	- description: TX
  items:
	- description: RX

> 
> Thanks,
> Conor.