linux-kernel - Re: [PATCH] char/tty_io: fix legacy pty name when more than 256 pty devices are requested

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Date:	Thu, 10 Sep 2009 12:17:28 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Mauro Carvalho Chehab <mchehab@...radead.org>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Alan Cox <alan@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Kay Sievers <kay.sievers@...y.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: [PATCH] char/tty_io: fix legacy pty name when more than 256 pty
 devices are requested

On 09/10/2009 12:12 PM, Mauro Carvalho Chehab wrote:
> 
> +1. Reusing the namespace after tty[p-za-e][0-9a-f] doesn't seem to be good, IMHO.
> 

I think it's better to extend the strings with the current prefixes than
to burn the virgin ttyf* prefix.

> In the case of the BSD sockets, the patch is not just an userless fix. This is
> interesting when some applications are ported from other Unix'es and still uses BSD
> pty's, since several other Unix flavors were defining a higher namespace size.
> 
> For example, on zOS Unix, a pty device seems to allow up to 10.000 pty numbers (in the
> specific case of zOS Unix, they seem to be defined as /dev/[pt]typ[0-9]...) as shown at:
> 	www.redbooks.ibm.com/redbooks/pdfs/sg245228.pdf
> 

Yes, but you have to port the application *anyway* do deal with the
namespace.  BSD tty allocation is done largely by each application,
which makes it even worse.  Furthermore, there is the static allocation
issue, so unless there is a concrete application which needs this *and*
cannot be ported to Unix98 ptys (which is the Right Thing[TM] to do) I
think Alan is right.

	-hpa
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