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Message-ID: <940f74fd-51b8-4158-9f40-c9ffa9a27ccb@VA3EHSMHS013.ehs.local>
Date: Wed, 7 Oct 2009 17:47:58 -0600
From: John Linn <John.Linn@...inx.com>
To: "John Williams" <john.williams@...alogix.com>,
<grant.likely@...retlab.ca>
CC: "Linux Kernel list" <linux-kernel@...r.kernel.org>,
"Michal Simek" <michal.simek@...alogix.com>,
"David DeBonis" <ddeboni@...inx.com>,
"Stephen Neuendorffer" <stephenn@...inx.com>,
"devicetree-discuss" <devicetree-discuss@...ts.ozlabs.org>
Subject: RE: Xilinx SYSACE driver and 8-bit attachment
> -----Original Message-----
> From: John Williams [mailto:john.williams@...alogix.com]
> Sent: Wednesday, October 07, 2009 5:45 PM
> To: grant.likely@...retlab.ca
> Cc: Linux Kernel list; Michal Simek; John Linn; David DeBonis; Stephen Neuendorffer; devicetree-
> discuss
> Subject: Re: Xilinx SYSACE driver and 8-bit attachment
>
> On Wed, Oct 7, 2009 at 11:34 PM, Grant Likely <grant.likely@...retlab.ca> wrote:
> > [Added devicetree-discuss to cc: list]
> >
> > On Wed, Oct 7, 2009 at 1:13 AM, John Williams
> > <john.williams@...alogix.com> wrote:
> >> Hi Grant (it's your driver :) and David D ( and your DTS generator :)
> > [...]
> >> if (of_find_property(op->node, "8-bit", NULL))
> > [...]
> >> doesn't match the properties generated by Xilinx's device tree generator:
> > [...]
> >> xlnx,mem-width = <0x8>;
> >>
> >> So, the question is, which should change?
> >
> > Well, obviously its a device tree generator bug, the driver code is
> > perfect. :-P
>
> How did I know you'd say that? :)
>
> > In all seriousness though, the '8-bit' property has been present for a
> > while now and needs to be retained to not break existing users. It
> > would be okay for the driver to be modified to *also* check for the
> > xlnx,mem-width property, but the better solution is to modify the
> > device tree generator. Plus, the '8-bit' property is the documented
> > binding in Documentation/powerpc/dts-bindings/xilinx.txt
>
> I tend to agree - but I also tend think that putting funky, arbitrary
> output strings in the DTS generator is also a bad idea.
>
> In this case, my vote is leaning towards adding a test for
> "xlnx,mem-width = <..>" to the driver, in addition to the existing
> "8-bit" tag to keep back compatability.
>
> How would you feel about that?
>
> In future, for new Xilinx drivers I think the default binding should
> be inspired by what comes from the DTS generator automatically, with
> out any special per-device hacks. This has a natural tendency towards
> minimum pain I think.
Agreed. This was special legacy is the only reason it warranted it.
>
> John
> --
> John Williams, PhD, B.Eng, B.IT
> PetaLogix - Linux Solutions for a Reconfigurable World
> w: www.petalogix.com p: +61-7-30090663 f: +61-7-30090663
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