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Date:   Tue, 6 Apr 2021 08:27:50 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     "Maciej W. Rozycki" <macro@orcam.me.uk>
Cc:     Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        Khalid Aziz <khalid@gonehiking.org>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Matthew Wilcox <willy@infradead.org>,
        Hannes Reinecke <hare@suse.com>,
        Ondrej Zary <linux@rainbow-software.org>,
        linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
        Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH 2/8] Buslogic: remove ISA support
Message-ID: <20210406062750.GA6277@lst.de>
References: <20210331073001.46776-1-hch@lst.de> <20210331073001.46776-3-hch@lst.de> <alpine.DEB.2.21.2104031805520.18977@angie.orcam.me.uk>
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On Sat, Apr 03, 2021 at 06:58:24PM +0200, Maciej W. Rozycki wrote:
>  Last but not least I do hope you do not plan to retire ISA DMA bounce 
> buffering support for drivers/block/floppy.c, as there is hardly an 
> alternative available (I do have a single SCSI<->FDD interface built 
> around an Intel 8080 CPU, in the half-height 5.25" drive form factor, but 
> such devices are exceedingly rare, and then you need a suitable parallel 
> SCSI host too).

The floppy driver already uses its own bounce buffering for addressing
limitations, and only the kernel bounce buffering to avoid getting
fed highmem patches.  Please take a look at this series to clean up the
latter:

https://lore.kernel.org/linux-block/20210406061755.811522-1-hch@lst.de/T/#u

>  Would it be feasible to convert it and any other drivers for ISA DMA 
> devices (like those support for which you propose to remove here) still 
> have users who could verify operation to the IOMMU framework?

I've converted the only once that still has signs of having users in
the last 10 or so years.