Date: Fri, 9 Apr 2010 23:54:13 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: guenter.roeck@ericsson.com, linux-kernel@vger.kernel.org,
       Yinghai <yinghai.lu@oracle.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Bjorn Helgaas <bjorn.helgaas@hp.com>,
       Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
       "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
       "x86@kernel.org" <x86@kernel.org>, Andy Isaacson <adi@hexapodia.org>,
       Thomas Renninger <trenn@suse.de>
Subject: Re: [PATCH] x86: Reserve legacy VGA MMIO area for x86_64 as well as
 x86_32
Message-ID: <20100409235413.1167ff0c@lxorguk.ukuu.org.uk>
In-Reply-To: <4BBFAD49.3000208@zytor.com>
References: <20100407210628.28364.96982.stgit@bob.kio>
	<201004071705.07176.bjorn.helgaas@hp.com>
	<4BBD13C3.2060404@oracle.com>
	<201004091004.39857.bjorn.helgaas@hp.com>
	<4BBF5987.3010100@zytor.com>
	<4BBF626A.3060800@oracle.com>
	<4BBF70BC.3080809@zytor.com>
	<1270839357.1477.758.camel@groeck-laptop>
	<4BBF89FE.5040909@zytor.com>
	<1270845108.1477.784.camel@groeck-laptop>
	<4BBF91C6.9090701@zytor.com>
	<20100409234245.4081994a@lxorguk.ukuu.org.uk>
	<4BBFAD49.3000208@zytor.com>
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> No they're not.  The 0xa0000...0xbffff range has been a legacy video
> area since the very first PC (although the first PC only used
> 0xb0000..0xbffff, 0xa0000..0xbffff was declared reserved at that time.)

Depending on your definition of "PC". Quite a few early MSDOS systems had
video elsewhere. Some embedded systems without video use the space for
other stuff. Lots of ISA 386/486 PCs had cards borrowing the unused bits
of video space.

> I'm wondering what those legitimate reasons are.  This is particularly
> so since it affects our ability to deal with very early errors, long
> before we have enumerated anything.  At this point we can at least lay
> down bytes in the video area and hope the user can see them.

Thats why you have the bios equipment byte and video queries.
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