[RFC PATCH 2/2] board: ti: am65x: Move to using Extension framework

[Köry Maincent]

On Wed, 4 Oct 2023 15:39:23 +0300
Roger Quadros <rogerq at kernel.org> wrote:

Hello,
Thanks for adding me in cc. Also it seems I forgot to add myself to MAINTAINERS
for the extension_board.c file.

> >>> Before this goes too far I think this should move to using a linker
> >>> list to declare the driver (or a driver-model driver if you prefer,
> >>> but that might be overkill).  
> 
> So I've been working on this on the side and got linker list way working
> with custom script booting but as soon as I move to standard boot flow
> it no longer works. This is because there is no code in place to
> apply the overlay and pass it to next stage e.g. EFI.
> 
> I see the following note at
> https://elixir.bootlin.com/u-boot/latest/source/boot/bootmeth_efi.c#L304
> 
> "
>                 /*
>                  * TODO: Apply extension overlay
>                  *
>                  * Here we need to load and apply the extension overlay. This
> is
>                  * not implemented. See do_extension_apply(). The extension
>                  * stuff needs an implementation in boot/extension.c so it is
>                  * separate from the command code. Really the extension stuff
>                  * should use the device tree and a uclass / driver interface
>                  * rather than implementing its own list
>                  */
> "

I agreed that the extension implementation should move in boot/extension.c or
common for general use. I am wondering what the advantage of creating an uclass
interface?
I am not an uclass expert but there is no per driver ops and usage. What do you
dislike about using its own list?

> Another note at
> https://elixir.bootlin.com/u-boot/latest/source/cmd/extension_board.c#L198
> 
> "/* extensions should have a uclass - for now we use UCLASS_SIMPLE_BUS uclass
> */"
> 
> So are we better off implementing a class driver for extension stuff?

I think the first point should be to move it in common or boot and makes it
generic for using the extension function everywhere. I will let Simon answer
about the uclass part.

Regards,