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From: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
To: Avi Kivity <avi@redhat.com>
Cc: Jordan Justen <jljusten@gmail.com>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] Implement PC port80 debug register.
Date: Tue, 30 Jun 2009 01:18:41 +0200	[thread overview]
Message-ID: <4A494BD1.6040301@gmx.net> (raw)
In-Reply-To: <4A48DF8B.7050606@redhat.com>

On 29.06.2009 17:36, Avi Kivity wrote:
> On 06/29/2009 06:26 PM, Jordan Justen wrote:
>> Well, I am not sure if this it globally the case for PC motherboards,
>> but in my experience, it has been read/write.
>
> Why would software ever need to read it?  You want a monitor command
> so the user can read it.  I don't recall ever seeing a read of port 80
> (I don't have any objections to that though).

AFAIK some Linux versions use port 0x80 reads (instead of writes) for
some delays (grep for REALLY_SLOW_IO) because some hardware vendors
started abusing writes to port 0x80 for communication with embedded
controllers.

Regards,
Carl-Daniel

-- 
http://www.hailfinger.org/

      parent reply	other threads:[~2009-06-29 23:18 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-06-29  8:05 [Qemu-devel] [PATCH] Implement PC port80 debug register Jordan Justen
2009-06-29 13:47 ` Anthony Liguori
2009-06-29 14:17   ` Paul Brook
2009-06-29 14:23   ` Avi Kivity
2009-06-29 14:34     ` Chris Lalancette
2009-06-29 15:26     ` Jordan Justen
2009-06-29 15:31       ` Anthony Liguori
2009-06-29 16:07         ` Jordan Justen
2009-06-29 17:11           ` Avi Kivity
2009-06-29 18:39             ` Anthony Liguori
2009-06-29 18:43               ` Avi Kivity
2009-06-29 18:46               ` Alexander Graf
2009-06-29 18:57                 ` Avi Kivity
2009-06-29 19:00                 ` Jordan Justen
2009-06-29 19:02               ` Jordan Justen
2009-07-01  7:39               ` Jordan Justen
2009-07-09 18:58                 ` Anthony Liguori
2009-06-29 15:36       ` Avi Kivity
2009-06-29 21:53         ` Jamie Lokier
2009-06-29 23:18         ` Carl-Daniel Hailfinger [this message]

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