linux-kernel - Re: [PATCH] allow alternative name for PXA serial console

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Message-ID: <CAL0eWdHwwcMUc2m0MSihV5R2caQJ7kp579w4M0X=hNZ=ccoRig@mail.gmail.com>
Date:	Wed, 13 Mar 2013 04:03:16 +0400
From:	Сергей Янович <ynvich@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Jiri Slaby <jslaby@...e.cz>, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] allow alternative name for PXA serial console

On 13 March 2013 03:39, Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
> On Wed, Mar 13, 2013 at 03:34:59AM +0400, Сергей Янович wrote:
>> --------------------
>> * Non-8250 serial port support
>> *
>> PXA serial port support (SERIAL_PXA) [Y/n/?] y
>>   Console on PXA serial port (SERIAL_PXA_CONSOLE) [Y/n/?] y
>>   as /dev/ttySA[0-3] (SERIAL_PXA_TTYSA_NAME) [N/y/?] (NEW)
>
> Please make it sane for the single line it is on.

"PXA serial port with SA-1100 major"
"PXA serial port with SA-1100 major number"
"PXA serial port with SA-1100 major device number"

Could anything like that be acceptable?

How long a line could be?

>> Maybe I am missing something obvious, but it seems that such a
>> collision is a kernel bug. Someone assumed that PXA cannot have a 8250
>> tty device and used 8250's parameters in PXA tty driver.
>
> Yes, someone must have messed up, so care to find the root problem here?

Two drivers try to use the same resource. It was in pre-git era, so it
difficult to find out exactly. I would guess that that 8250 have
precedence by at least 5 years. But it is almost guaranteed that lots
of people depend on PXA console having ttyS0 name. So simple
s/ttyS/ttySA/ is not a solution. My patch preserves status quo by
default, but allows to have a correct workaround for those who face a
collision. By correct I mean that it will not create a new collision
since a system cannot run on both SA-1100 and PXA270 at the same time.
This assumption is already documented in
arch/arm/mach-pxa/include/mach/irqs.h line 94.
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