Subject: Re: [PATCH v2 3/3] arch/*/: remove CONFIG_VIRT_TO_BUS

From: Michael Schmitz <[email-masked]>
Date: Sat, 18 Jun 2022 13:06:40 +1200

Arnd,

Am 18.06.2022 um 00:57 schrieb Arnd Bergmann:
> From: Arnd Bergmann <[email-masked]>
>
> All architecture-independent users of virt_to_bus() and bus_to_virt()
> have been fixed to use the dma mapping interfaces or have been
> removed now.  This means the definitions on most architectures, and the
> CONFIG_VIRT_TO_BUS symbol are now obsolete and can be removed.
>
> The only exceptions to this are a few network and scsi drivers for m68k
> Amiga and VME machines and ppc32 Macintosh. These drivers work correctly
> with the old interfaces and are probably not worth changing.

The Amiga SCSI drivers are all old WD33C93 ones, and replacing 
virt_to_bus by virt_to_phys in the dma_setup() function there would 
cause no functional change at all.

drivers/vme/bridges/vme_ca91cx42.c hasn't been used at all on m68k (it 
is a PCI-to-VME bridge chipset driver that would be needed on 
architectures that natively use a PCI bus). I haven't found anything 
that selects that driver, so not sure it is even still in use??

That would allow you to drop the remaining virt_to_bus define from 
arch/m68k/include/asm/virtconvert.h.

I could submit a patch to convert the Amiga SCSI drivers to use 
virt_to_phys if Geert and the SCSI maintainers think it's worth the churn.

32bit powerpc is a different matter though.

Cheers,

	Michael