linux-kernel - Re: [PATCH] of: change fixup of dma-ranges size to error

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Message-ID: <CAL_Jsq+GLBtaezUiTbm0DAA2+MjcvxAcCsS-qJrr05YcTO5tdw@mail.gmail.com>
Date:   Thu, 6 Apr 2017 09:03:50 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Frank Rowand <frowand.list@...il.com>
Cc:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] of: change fixup of dma-ranges size to error

On Thu, Apr 6, 2017 at 1:18 AM,  <frowand.list@...il.com> wrote:
> From: Frank Rowand <frank.rowand@...y.com>
>
> of_dma_get_range() has workaround code to fixup a device tree that
> incorrectly specified a mask instead of a size for property
> dma-ranges.  That device tree was fixed a year ago in v4.6, so
> the workaround is no longer needed.  Leave a data validation
> check in place, but no longer do the fixup.  Move the check
> one level deeper in the call stack so that other possible users
> of dma-ranges will also be protected.
>
> The fix to the device tree was in
> commit c91cb9123cdd ("dtb: amd: Fix DMA ranges in device tree").

NACK. This was by design. You can't represent a size of 2^64 or 2^32.
Well, technically you can for the latter, but then you have to grow
#size-cells to 2 for an otherwise all 32-bit system which seems kind
of pointless and wasteful. You could further restrict this to only
allow ~0 and not just any case with bit 0 set.

I'm pretty sure AMD is not the only system. There were 32-bit systems too.

Rob