linux-kernel - Re: [PATCH 01/11] resolve PXA<->8250 serial device address conflict

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Message-ID: <1385980005.12531.21.camel@host5.omatika.ru>
Date:	Mon, 02 Dec 2013 14:26:45 +0400
From:	Sergei Ianovich <ynvich@...il.com>
To:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	"open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH 01/11] resolve PXA<->8250 serial device address conflict

On Mon, 2013-12-02 at 11:49 +0200, Heikki Krogerus wrote:
> On Mon, Dec 02, 2013 at 01:23:58PM +0400, Sergei Ianovich wrote:
> > On Mon, 2013-12-02 at 11:02 +0200, Heikki Krogerus wrote:
> > > On Sun, Dec 01, 2013 at 10:26:14AM +0400, Sergei Ianovich wrote:
> > > > PXA serial ports have "standard" UART names (ttyS[0-3]), major
> > > > device number (4) and first minor device number (64) by default.
> > > > 
> > > > If the system has extra 8250 serial port hardware in addition
> > > > to onboard PXA serial ports, default settings produce a device
> > > > allocation conflict.
> > > > 
> > > > The patch provides a configuration option which can move onboard
> > > > ports out of the way of 8250_core by assigning a different (204)
> > > > major number and corresponding device names (ttySA[0-3]).
> > > > 
> > > <snip>
> > > 
> > > If drivers/tty/serial/pxa.c was converted to an other probe driver for
> > > the 8250, this would not be an issue.
> > 
> > It seems that my patch is not going to be accepted. However, there is a
> > device which has both PXA ports and a additional 8250 accent chip. As a
> > result, there is a device allocation conflict. For the device to be
> > usable the conflict needs to be resolved.
> > 
> > Do you mean that drivers/tty/serial/pxa.c needs to be rewritten to
> > support lp8x4x special case?
> 
> Sorry I was not clear. I was suggesting that drivers/tty/serial/pxa.c
> would be converted to drivers/tty/serial/8250/8250_pxa.c since it
> looks to me like just an other 16x50 compatible UART. That would fix
> the issue with the name conflict. You would then simply register 8250
> ports from two probe drivers (drivers/tty/serial/8250/8250_pxa.c and
> drivers/tty/serial/8250/8250_lp8x4x.c).
> 
> Depending on the order you register your platform devices (which you
> decide in your platform code), but let's say the pxa gets registered
> first and let's say it only has one port. You will then have in your
> system /dev/ttyS0 for the pxa port and /dev/ttyS[1-4] for the other
> UART.
> 
> I hope I was able to explain what I mean this time :)

Sorry, I wasn't clear as well. I got it right the first time. You mean
pxa.c needs to merged into 8250. This will solve the conflict in
question, and do it the right way. However, this will be a *much* bigger
patch, and it will affect everyone on pxa.

Who makes the decision which way to go?

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