linux-kernel - Re: [PATCH 2/3] dt-bindings: spi: Add DT schema for Tegra SPIDEV controller

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Message-ID: <e95f870f-1309-4ac3-a16f-ce58b02dc817@nvidia.com>
Date: Wed, 27 Nov 2024 15:54:52 +0000
From: Jon Hunter <jonathanh@...dia.com>
To: Mark Brown <broonie@...nel.org>, Vishwaroop A <va@...dia.com>,
 krzk+dt@...nel.org
Cc: robh@...nel.org, conor+dt@...nel.org, thierry.reding@...il.com,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-tegra@...r.kernel.org, linux-spi@...r.kernel.org
Subject: Re: [PATCH 2/3] dt-bindings: spi: Add DT schema for Tegra SPIDEV
 controller

Hi Mark, Krzysztof,

On 26/11/2024 13:56, Mark Brown wrote:
> On Tue, Nov 26, 2024 at 01:45:28PM +0000, Vishwaroop A wrote:
> 
>> +            # NVIDIA Tegra SPIDEV Controller device
>> +          - nvidia,tegra-spidev
> 
> All the issues with having spidev nodes directly in the DT also apply if
> you add a prefix onto it.  Whatever is attached to the SPI controller
> needs to be described, not just a placeholder like this.

Chatting with Vishwaroop, what he is trying to accomplish with this 
patchset it to have a pseudo SPI device that we can control from userspace.

On the Tegra Jetson boards we have a 40-pin expansion header similar to 
what is found on boards like Raspberry Pi and allows users to connect 
various cards to. By having a pseudo device we can interact with 
different SPI devices.

Yes by default nothing is connected and so there is nothing to talk to. 
However, this does enable us to do SPI loopback testing for example.

So I am wondering if it would be acceptable to having some generic dummy 
device-tree compatible string for this? I guess it does not need to be 
Tegra specific.

Thanks
Jon

-- 
nvpublic