linux-kernel - Re: [PATCH 1/3] dt-bindings: spi: add SpacemiT K1 SPI support

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Message-ID: <20250918001632-GYA1270371@gentoo.org>
Date: Thu, 18 Sep 2025 08:16:32 +0800
From: Yixun Lan <dlan@...too.org>
To: Alex Elder <elder@...cstar.com>
Cc: broonie@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, linux-spi@...r.kernel.org,
	devicetree@...r.kernel.org, paul.walmsley@...ive.com,
	palmer@...belt.com, aou@...s.berkeley.edu, alex@...ti.fr,
	p.zabel@...gutronix.de, spacemit@...ts.linux.dev,
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: spi: add SpacemiT K1 SPI support

Hi Alex,

On 18:40 Wed 17 Sep     , Alex Elder wrote:
> On 9/17/25 6:15 PM, Yixun Lan wrote:
> > Hi Alex,
> > 
> > On 17:07 Wed 17 Sep     , Alex Elder wrote:
> >> Add support for the SPI controller implemented by the SpacemiT K1 SoC.
> >>
> >> Signed-off-by: Alex Elder <elder@...cstar.com>
> >> ---
> >>   .../bindings/spi/spacemit,k1-spi.yaml         | 94 +++++++++++++++++++
> >>   1 file changed, 94 insertions(+)
> >>   create mode 100644 Documentation/devicetree/bindings/spi/spacemit,k1-spi.yaml
> >>
> >> diff --git a/Documentation/devicetree/bindings/spi/spacemit,k1-spi.yaml b/Documentation/devicetree/bindings/spi/spacemit,k1-spi.yaml
> >> new file mode 100644
> >> index 0000000000000..5abd4fe268da9
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/spi/spacemit,k1-spi.yaml
..
> >> +
> >> +  spacemit,k1-ssp-id:
> >> +    description: SPI controller number
> >> +    $ref: /schemas/types.yaml#/definitions/uint32
> > could you explain a little bit why this vendor specific property should
> > be introduced? I took a look at the code, and didn't get the reason
> > behind.. or what's the problem of simply using "pdev->id"?
> 
> This property was carried over from the vendor code.  It is
inherit from vendor code isn't a valid reason

> optional, and if it isn't specified, the platform device ID (-1)
> will be used.  It's just intended to provide a well-defined ID
> for a particular SPI controller.
> 
while looking at the code, it seems you can use alias to map specific id
to the spi controller, it even can do non-linear map, something like
	spi0 = &spi3;

plese check of_alias_get_id()

note, I haven't actually verified on board, just look through the code

> > we should really be careful to introduce vendor specific property..
> 
> If there were a standard way of doing this I'd love to use it.
> 
> And if it isn't necessary, please just explain to me why.  I
> have no problem removing it.
> 
on the opposite, please have explicit good reason to introduce vendor
speifici property, and if there is generic way, then we shouldn't do it

-- 
Yixun Lan (dlan)