Re: [RFC PATCH v2 2/6] bus/cdx: add the cdx bus driver

Jason Gunthorpe
2022-08-24T23:32:02Z

On Wed, Aug 24, 2022 at 02:11:48PM +0200, Greg KH wrote:
> > We can share the RFC in case you are interested in looking at code flow
> > using the of_dynamic approach.
>
> Please no more abuse of the platform device.

Last time this came up there was some disagreement from the ARM folks,
they were not keen on having xx_drivers added all over the place to
support the same OF/DT devices just discovered in a different way. It is
why ACPI is mapped to platform_device even in some cases.

I think if you push them down this path they will get resistance to
get the needed additional xx_drivers into the needed places.

> If your device can be discovered by scanning a bus, it is not a platform
> device.

A DT fragment loaded during boot binds a driver using a
platform_driver, why should a DT fragment loaded post-boot bind using
an XX_driver and further why should the CDX way of getting the DT
raise to such importantance that it gets its own cdx_driver ?

In the end the driver does not care about how the DT was loaded.
None of these things are on a discoverable bus in any sense like PCI
or otherwise. They are devices described by a DT fragement and they
take all their parameters from that chunk of DT.

How the DT was loaded into the system is not a useful distinction that
raises the level of needing an entire new set of xx_driver structs all
over the tree, IMHO.

Jason