efi_loader breakage

[AKASHI Takahiro]

On Tue, Apr 26, 2022 at 07:07:13PM +0200, Mark Kettenis wrote:
> commit d97e98c887ed8fa4a339350c02f093f03cd1cf4d breaks the OpenBSD
> bootloader.  Or rather, it seems that this breaks access to raw
> devices through the UEFI interfaces, which is something the OpenBSD
> bootloader relies on.
> 
> After this commit we end up calling dev_read() and dev_write() instead
> of blk_dread() and blk_dwrite().  But dev_read() and dev_write() only
> work if dev_get_blk() returns a valid struct blkdev, and that handles
> only for UCLASS_PARTITION.  But when accessing raw devices we have a
> UCLASS_BLK.

Probably I forgot this use case.

> The easy fix would be to support UCLASS_BLK in dev_get_blk(), but that
> function has an explicit comment saying:

The best way to do is to modify efi_disk_rw_blocks().

-Takahiro Akashi

>         /*
>          * We won't support UCLASS_BLK with dev_* interfaces.
>          */
> 			  
> So I'm a bit at a loss what is needed here.