linux-kernel - Re: [RFC PATCH] tty: serial: Add 8250-core based omap driver

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Date:	Thu, 3 Jul 2014 00:34:11 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Robert Nelson <robertcnelson@...il.com>
Cc:	Aaro Koskinen <aaro.koskinen@....fi>, Felipe Balbi <balbi@...com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux kernel <linux-kernel@...r.kernel.org>,
	linux-serial@...r.kernel.org,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linux ARM Kernel Mailing List 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH] tty: serial: Add 8250-core based omap driver

* Robert Nelson <robertcnelson@...il.com> [140702 12:27]:
> On Wed, Jul 2, 2014 at 2:09 PM, Aaro Koskinen <aaro.koskinen@....fi> wrote:
> > Hi,
> >
> > On Wed, Jul 02, 2014 at 11:09:32AM -0500, Felipe Balbi wrote:
> >> > It has been only tested as console UART.
> >> > The tty name is ttyS based instead of ttyO. How big is the pain here,
> >> > what could be the easiest way to provide compatibility?
> >>
> >> have been considering that myself for months. You could pass an optional
> >> argument to serial8250_register_8250_port() but that only solves part of
> >> the problem :-(

Some kind of compability layer sure would be nice.

> > When ttyS -> ttyO change was done on OMAP, compatibility was not an issue.
> > Why should we care about it now?
> 
> It would be a good opportunity to force everyone to update their bootloader. ;)
> 
> Besides the BeagleBoard forum is quiet now, no one is complaining
> about that old (ttyS -> ttyO) transition anymore..

How about a Kconfig option to provide ttyO by default? The not even
do that if kernel has cmdline option nottyomap.
 
> I'll just end up carrying a patch like, to support bb.org users over
> the transition..
> 
> https://github.com/RobertCNelson/stable-kernel/blob/v3.7.x/patches/omap_beagle/0004-zeroMAP-Open-your-eyes.patch

Heh. Just to summarize the reason ttyO needs to be a separate name
and device entry from ttyS is because we also have external 8250
devices on GPMC and hotplug busses.

Regards,

Tony
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