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Subject: Re: [PATCH v2 3/3] arch/*/: remove CONFIG_VIRT_TO_BUS
To:     Arnd Bergmann <arnd@kernel.org>, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20220617125750.728590-1-arnd@kernel.org>
 <20220617125750.728590-4-arnd@kernel.org>
Cc:     Arnd Bergmann <arnd@arndb.de>, Jakub Kicinski <kuba@kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>,
        iommu@lists.linux-foundation.org,
        Khalid Aziz <khalid@gonehiking.org>,
        "Maciej W . Rozycki" <macro@orcam.me.uk>,
        Matt Wang <wwentao@vmware.com>,
        Miquel van Smoorenburg <mikevs@xs4all.net>,
        Mark Salyzyn <salyzyn@android.com>,
        linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org,
        linux-alpha@vger.kernel.org, linux-m68k@lists.linux-m68k.org,
        linux-parisc@vger.kernel.org, Denis Efremov <efremov@linux.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Michael Ellerman <mpe@ellerman.id.au>
From:   Michael Schmitz <schmitzmic@gmail.com>
Message-ID: <6ba86afe-bf9f-1aca-7af1-d0d348d75ffc@gmail.com>
Date:   Sat, 18 Jun 2022 13:06:40 +1200
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Arnd,

Am 18.06.2022 um 00:57 schrieb Arnd Bergmann:
> From: Arnd Bergmann <arnd@arndb.de>
>
> 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