RE: Xilinx SYSACE driver and 8-bit attachment

From: John Linn
Date: Wed Oct 07 2009 - 19:49:24 EST


> -----Original Message-----
> From: John Williams [mailto:john.williams@xxxxxxxxxxxxx]
> Sent: Wednesday, October 07, 2009 5:45 PM
> To: grant.likely@xxxxxxxxxxxx
> 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@xxxxxxxxxxxx> wrote:
> > [Added devicetree-discuss to cc: list]
> >
> > On Wed, Oct 7, 2009 at 1:13 AM, John Williams
> > <john.williams@xxxxxxxxxxxxx> 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


This email and any attachments are intended for the sole use of the named recipient(s) and contain(s) confidential information that may be proprietary, privileged or copyrighted under applicable law. If you are not the intended recipient, do not read, copy, or forward this email message or any attachments. Delete this email message and any attachments immediately.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/