linux-kernel - Re: [PATCH] Add possibility to set /dev/tty number

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Message-ID: <20160104225544.158dc847@lxorguk.ukuu.org.uk>
Date:	Mon, 4 Jan 2016 22:55:44 +0000
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	"Austin S. Hemmelgarn" <ahferroin7@...il.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Pierre Paul MINGOT <mingot.pierre@...il.com>, jslaby@...e.cz,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Add possibility to set /dev/tty number

> > If the console isn't initialized by userspace, is any of that space
> > still really being used?  Have you tried that?
> I'm pretty certain that most of the space that gets taken up by the 
> scrollback buffer and screen isn't directly used unless the console is 
> used, but there are still structures that get allocated at driver 
> instantiation for each VT, including the device structures and such.

So fix that instead.

And really for low memory embedded why do you even have the VT layer in
your system in the first place ?

> > If we remove the number of devices, those "broken" userspace programs
> > will also break, so that implies that we should not allow this change.
> No, the software should just need to be recompiled (I've tested this 
> with ConsoleKit, which also fails gracefully when it tires to open a tty 
> device that doesn't exist), or adapted to dynamically detect the number 
> of TTYs (like it should have in the first place for portability reasons).

We don't do regressions.

> device drivers). I doubt that it will work out to any more than 16k size 
> difference, but that's still a few more pages (on most systems) that 
> could be used for other things.

And those embedded devices can almost certainly save more by just not
including the vt layer.

Alan
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