From mboxrd@z Thu Jan  1 00:00:00 1970
From: Rene Herman <rene.herman@keyaccess.nl>
Subject: Re: [patch 2/2] 8250_pnp: register x86 COM ports at the conventional
 ttyS names
Date: Thu, 17 Jan 2008 00:34:05 +0100
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References: <9MjWa-VI-9@gated-at.bofh.it> <9MjWb-VI-11@gated-at.bofh.it> <9MlEG-3Mx-13@gated-at.bofh.it> <9Mmra-56f-29@gated-at.bofh.it> <E1JFEwb-0000zs-2q@be1.7eggert.dyndns.org> <478E6C20.2030005@zytor.com>
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To: "H. Peter Anvin" <hpa@zytor.com>
Cc: 7eggert@gmx.de, Bjorn Helgaas <bjorn.helgaas@hp.com>, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Russell King <rmk+serial@arm.linux.org.uk>, Jeff Garzik <jeff@garzik.org>, Andrew Morton <akpm@linux-foundation.org>, Alan Cox <alan@lxorguk.ukuu.org.uk>

On 16-01-08 21:42, H. Peter Anvin wrote:

> Bodo Eggert wrote:
>> 
>> BTW1: These addresses may be used to detect ports on non-standard 
>> addresses, but unfortunately they don't tell the IRQ.
>> 
>> BTW2: When I submitted a patch using the BIOS data area, I was told 
>> that it might not exist on systems booting from non-PC firmware. This 
>> claim was not yet backed with any knowledge, nor did anybody suggest a 
>> way to detect this situation.
> 
> This is, of course, true.  It doesn't exactly help that some (most?) 
> non-PC firmware at least mimic the BIOS data area.
> 
> In this particular case, there is some minor sanity-checking that can be
> done: the values should be nonzero and aligned 8.

The number of places expected to contain something sensible should I believe 
first be verified at 0x410 -- the equipment word. Bits 11-9 (0x0e00) should 
be the number of serial ports, 0 to 4 (so 5-7 is also a sanity check) and if 
BIOSes can be expected to zero out the non-used base-addresses (at 0x400, 
0x402, 0x404, 0x406) that's another sanity check. Don't know if they can 
though...

Rene.