linux-kernel - Re: linux-next: Tree for Nov 27 (scsi/aha1542)

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Message-ID: <20181128065450.GA20211@lst.de>
Date:   Wed, 28 Nov 2018 07:54:50 +0100
From:   Christoph Hellwig <hch@....de>
To:     James Bottomley <James.Bottomley@...senPartnership.com>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Randy Dunlap <rdunlap@...radead.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-scsi <linux-scsi@...r.kernel.org>,
        Christoph Hellwig <hch@....de>
Subject: Re: linux-next: Tree for Nov 27 (scsi/aha1542)

On Tue, Nov 27, 2018 at 09:41:24PM -0800, James Bottomley wrote:
> Yes, it's because dma_addr_t can be u64 on pae systems but
> isa_virt_to_bus only ever returns unsigned long (because an ISA
> physical address can only be 24 bits).
> 
> I think this is the fix; there doesn't seem to be much point converting
> to do_div given all the limitations.

Yes, something along these lines should fix it.  I don't have the code
in front of me, but I vaguely remember there is a second division like
this, though.  It might be worth to factor the calculation into a helper
with a comment like the message above explaining it.