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/
prev 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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