linux-kernel - Re: [PATCH 3.13 35/99] tty: Set correct tty name in active sysfs attribute

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Date:	Sat, 22 Feb 2014 08:40:24 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	David Herrmann <dh.herrmann@...il.com>,
	Hannes Reinecke <hare@...e.de>
CC:	Ray Strode <halfline@...il.com>, Kay Sievers <kay@...y.org>,
	Josh Boyer <jwboyer@...oraproject.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	Lennart Poettering <lennart@...ttering.net>,
	Jiri Slaby <jslaby@...e.cz>, Werner Fink <werner@...e.de>
Subject: Re: [PATCH 3.13 35/99] tty: Set correct tty name in active sysfs
 attribute

On 02/22/2014 08:25 AM, David Herrmann wrote:
> Hi
>
> On Fri, Feb 21, 2014 at 11:53 PM, Ray Strode <halfline@...il.com> wrote:
>> Hi,
>>
>> On Fri, Feb 21, 2014 at 11:01 AM, Kay Sievers <kay@...y.org> wrote:
>>> Why did the tty0 change to tty1 now? That doesn't look like a "driver
>>> name" vs. "device name" issue?
>>
>> I don't know if it's intentional, but the patch does:
>> +               int index = cs[i]->index;
>> ...
>> +               driver = cs[i]->device(cs[i], &index);
>>
>> which will presumably change the index from 0 to 1 because of this code:
>>
>> static struct tty_driver *vt_console_device(struct console *c, int *index)
>> {
>>         *index = c->index ? c->index-1 : fg_console;
>>         return console_driver;
>> }
>>
>> At least that's what it looks like is causing the problem from
>> browsing through the source a bit.
>
> Yepp, that's it. So if you configure the console to always be
> redirected to the foreground terminal, you simply bind it to tty0 and
> this file used to return tty0 then.
> With this patch, we actually return the foreground terminal instead,
> so tty0 is resolved to the real VT. This sounds like the correct
> behavior (even though it currently breaks poll() on this file). But if
> it breaks stuff, we should revert it and add a second file just like
> Peter suggested.

Or add sysfs entries for each console that exposes the device, so
that the underlying device is trivially discoverable, which is the
original problem.

Regards,
Peter Hurley

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