From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Cu55O-0006y3-Ps for qemu-devel@nongnu.org; Thu, 27 Jan 2005 03:33:07 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Cu55A-0006pQ-GI for qemu-devel@nongnu.org; Thu, 27 Jan 2005 03:32:54 -0500 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Cu55A-0006p5-4z for qemu-devel@nongnu.org; Thu, 27 Jan 2005 03:32:52 -0500 Received: from [62.210.169.120] (helo=the-doors.enix.org) by monty-python.gnu.org with esmtp (Exim 4.34) id 1Cu4sN-0005JH-8n for qemu-devel@nongnu.org; Thu, 27 Jan 2005 03:19:39 -0500 Received: from [127.0.0.1] (localhost [127.0.0.1]) by the-doors.enix.org (Postfix) with ESMTP id 00AF0401D1 for ; Thu, 27 Jan 2005 09:21:15 +0100 (CET) Message-ID: <41F8A421.5000807@enix.org> Date: Thu, 27 Jan 2005 09:19:45 +0100 From: Thomas Petazzoni MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] Port E9 hack, for debugging purposes References: <41E94DA5.9030809@enix.org> <41EBC1FB.8050506@enix.org> <41EC35AC.7090006@bellard.org> <41F818B3.1020106@enix.org> <41F82E78.4040909@mastros.biz> In-Reply-To: <41F82E78.4040909@mastros.biz> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig573791301025F46281B0133D" Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig573791301025F46281B0133D Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Hello, James Mastros a =E9crit : > I'm a bit of a newbie here, so perhaps this has already been covered,=20 > though I haven't seen it in the archives -- but why port E9, and not=20 > port 80? 80 seems to be the standard port for this sort of thing.=20 > (Though output seems to normally be two-digit-hex, and not ASCII-based.= ) >=20 > (Port E9 seems to be largely undefined, but marked as "reserved" in mos= t=20 > lists I've seen (or just not listed), so it seems possible, but=20 > unlikely, that things will think they know what should be connected=20 > there. OTOH, 80 is reserved for exactly what we're doing with it. On = > the third hand, the Linux kernel uses writes to port 0x80 to "slow down= "=20 > IO. I'm not sure what the interactions would be with this.) Mostly because this is the way Bochs implements it, and I thought it=20 would be nice to have it working exactly the same way on Qemu. This=20 feature is particularly interesting for people making their own toy OS.=20 It allows to have simple debugging possibilities without taking care of=20 writing a serial driver or a full-featured console driver. The Ralf's Brown Port List says that 0x80 is when writing a=20 "Manufacturing Diagnostics Port", but it doesn't say anything about readi= ng. Anyway, if Linux uses it to slow down I/O, this is not a good candidate=20 in my opinion for the E9-style hack. To sum up, I don't have any valid reason for choosing E9 instead of any=20 other, except that it's implemented that way in Bochs. Thomas --=20 PETAZZONI Thomas - thomas.petazzoni@enix.org http://thomas.enix.org - Jabber: thomas.petazzoni@jabber.dk http://kos.enix.org, http://sos.enix.org Fingerprint : 0BE1 4CF3 CEA4 AC9D CC6E 1624 F653 CB30 98D3 F7A7 --------------enig573791301025F46281B0133D Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFB+KQj9lPLMJjT96cRAoXPAJ9a97dZrkcsG03viyNHdYZB+byHiQCglnOd 8aA/Tj1Cly+1WrvTvAAWUnI= =yo/i -----END PGP SIGNATURE----- --------------enig573791301025F46281B0133D--