On 27/11/2024 16:09, Mark Brown wrote:
On Wed, Nov 27, 2024 at 03:54:52PM +0000, Jon Hunter wrote:
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.
I understand what he's trying to accomplish, it's the same thing as
what everyone who wants to put a raw spidev compatible in their DT is
trying to do. The way to do this would be something like a DT overlay
that describes whatever is actually connected, or just customise the DT
locally.
We could certainly use an overlay, but how do we handle the kernel side?
My understanding is that per patch 3/3 we need to reference a compatible
string the kernel is aware of. I guess we could use an existing one, but
feels like a massive hack. It would be nice if there is something
generic we can use for this like 'linux,spidev'.
I see that ACPI has something and it does print a warning that this
should not be used in production systems.
Jon
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nvpublic
