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From: Jeff Garzik <jgarzik@pobox.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Patrick Mochel <mochel@osdl.org>,
	"Grover, Andrew" <andrew.grover@intel.com>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Subtle semantic issue with sleep callbacks in drivers
Date: Thu, 17 Apr 2003 10:48:44 -0400	[thread overview]
Message-ID: <20030417144844.GC18749@gtf.org> (raw)
In-Reply-To: <1050586549.31414.41.camel@dhcp22.swansea.linux.org.uk>

On Thu, Apr 17, 2003 at 02:35:50PM +0100, Alan Cox wrote:
> On Mer, 2003-04-16 at 19:39, Patrick Mochel wrote:
> > I completely agree with Andy. We should not re-POST the video hardware, no
> > matter what. The idea behind ACPI is that the OS takes care of everything, 
> > including video save/restore. 
> 
> Outside of happyville ivory towers you probably have no choice. Only the
> BIOS knows stuff like the RAM timings, and some windows drivers just use
> the BIOS, others rely on being shipped compiled for the right variant of
> card they came with.

You are exactly right.

The video BIOS on a card often contains information that is found
-nowhere- else.  Not in the chip docs.  Not in a device driver.
Such information can and does vary from board-to-board, such as RAM
timings, while the chip remains unchanged.

You mention "windows drivers" above... even some Linux X drivers
depend on video BIOS.  The S3 Savage XFree86 driver, for example,
uses video BIOS quite heavily unless you tell it not to (or are on
a platform that prevents such).

WRT save and restore, it is certainly possible without video re-POST...

However, support such will require a monumental effort of testing and
debugging for each video board.  This monumental effort _will_ include
XFree86 hacking and possibly the additional of some save-n-restore
video drivers, if we do not wish to simply require CONFIG_FBDEV if
CONFIG_SUSPEND is set.

Video re-POST is simply a Real Life(tm) shortcut to that monumental effort.

	Jeff, originally an fbdev hacker back in the day...




  reply	other threads:[~2003-04-17 14:36 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-04-14 21:09 Subtle semantic issue with sleep callbacks in drivers Grover, Andrew
2003-04-16 18:39 ` Patrick Mochel
2003-04-16 19:36   ` Benjamin Herrenschmidt
2003-04-17 13:35   ` Alan Cox
2003-04-17 14:48     ` Jeff Garzik [this message]
2003-04-17 15:09       ` John Bradford
2003-04-17 15:09         ` Jeff Garzik
2003-04-17 15:47           ` John Bradford
2003-04-17 15:56             ` Jeff Garzik
2003-04-17 16:24               ` Alan Cox
2003-04-18  7:37             ` Greg KH
2003-04-18  7:51               ` John Bradford
2003-04-18  9:10               ` Russell King
2003-04-18 11:18                 ` Alan Cox
2003-04-18 11:30               ` Alan Cox
2003-04-29  8:28         ` Pavel Machek
2003-04-17 14:59     ` John Bradford
2003-04-17 15:04       ` Alan Cox
  -- strict thread matches above, loose matches on Subject: below --
2003-04-14 19:07 Grover, Andrew
2003-04-14 19:18 ` Benjamin Herrenschmidt
2003-04-14 19:56 ` Alan Cox
2003-04-23 15:34 ` Pavel Machek
2003-04-14 17:09 Grover, Andrew
2003-04-14 17:40 ` Benjamin Herrenschmidt
2003-04-23 15:29 ` Pavel Machek
2003-04-14 10:00 Benjamin Herrenschmidt
2003-04-14 10:11 ` Benjamin Herrenschmidt
2003-04-16 18:31 ` Patrick Mochel
2003-04-16 19:29   ` Benjamin Herrenschmidt
2003-04-23 15:32 ` Pavel Machek

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