linux-kernel - Re: [PATCH RFC 3/6] tty: Rename xilinx_uart -> cadence

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Date:	Wed, 5 Mar 2014 10:22:05 -0800
From:	Sören Brinkmann <soren.brinkmann@...inx.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Russell King <linux@....linux.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Michal Simek <michal.simek@...inx.com>,
	Peter Crosthwaite <peter.crosthwaite@...inx.com>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-serial@...r.kernel.org>, Olof Johansson <olof@...om.net>,
	Kevin Hilman <khilman@...aro.org>
Subject: Re: [PATCH RFC 3/6] tty: Rename xilinx_uart -> cadence_uart

Hi Arnd, Alan,

On Tue, 2014-03-04 at 11:16PM +0100, Arnd Bergmann wrote:
> On Tuesday 04 March 2014, One Thousand Gnomes wrote:
> > On Tue,  4 Mar 2014 09:17:26 -0800
> > Soren Brinkmann <soren.brinkmann@...inx.com> wrote:
> 
> > The following aspects of the change set are IMHO acceptable
> > 
> > - Cleaning up all the code formatting
> > - Update the driver comments and header to explain the Cadence/Xilinx
> >   thing
> > - change "Xilinx PS UART Support" text to "Cadence (Xilinx PS) Support"
> >   or similar wording in Kconfig
> > - Adding the cadence devicetree compatibility strings and inputs *in
> >   addition* to the existing ones.
> > - Documentation for the new options
> 
> I agree. I think it would also be nice to allow the standard clock names
> to be used as an alternative to the bogus ref_clk" and "aper_clk"
> names, but just like the compatible string, it's too late to remove
> support for the existing ones.
> 
> Regarding the "xlnx,xuartps" compatible string, even if we were to break
> backwards comptibility with the clocks, I would still want to see this
> string being used in addition to "cdns,uart-r1p8" so we have a way to
> detect possible changes that xilinx did on top of the r1p8 version.
> I also wonder if "cdns,uart-r1p8" is actually specific enough: r1p8
> looks like a version number rather than a name, and it seems possible
> that Cadence has produced more than one uart implemention in the past
> or will do another one in the future that is not just a different
> revision of this one but instead something completely different.

This was pretty much what I expected, but I wanted to at least try,
before documenting the binding.

So, to summarize:
 - don't rename the file
 - I think changing the Kconfig option might be possible, but doesn't
   really matter either. So, I'll leave it as is.
 - compat strings is the easy part, we can simple add another one
 - clock-names is not that forgiving. I'm inclined to document only the
   Cadence names, but allow both with issuing a deprecated warning when
   the Zynq ones are used. Then we can remove those probably a little
   later(?)
 - I'll do something like Alan's suggestion for the Kconfig prompt

Regarding how specific we can make the compat string: I asked myself the
same question when I looked at the docs. But they don't seem to use any
fancy names or anything. It's pretty much just a UART. The other problem
I have is, I'd have to double check what information, beyond what already
is in the Zynq TRM, is allowed to be disclosed.

	Thanks,
	Sören


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