linux-kernel - Re: [PATCH][RESEND] x86: Do not write to VGA memory space if CONFIG_VGA

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Date:	Mon, 19 Apr 2010 19:21:10 -0700
From:	Guenter Roeck <guenter.roeck@...csson.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"penberg@...helsinki.fi" <penberg@...helsinki.fi>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH][RESEND] x86: Do not write to VGA memory space if
	CONFIG_VGA_CONSOLE is undefined

On Mon, Apr 19, 2010 at 05:02:25PM -0400, H. Peter Anvin wrote:
> Hi Guenter,
> 
> I wanted to check where we are at... at the very least we should drop
> messages issued before initialization when isVGA != 1.
> 
> Since serial ports require initialization, I really don't want to send
> messages to the serial port before the port has been initialized, but
> obviously it would be good to initialize earlyprintk as early as at all
> possible.
> 
Moving setup_early_printk() around may be possible, but I do not know
the code good enough to take that risk. Even trying was a bad idea.

I could submit a patch to add some protection into early_printk(),
to ensure it does not write into VGA memory space if there is no VGA,
and do that without changing current semantics - specifically, still
write into VGA memory space even if setup_early_printk() was not called
yet, but if boot_params.screen_info.orig_video_isVGA is set.

I thought you indicated that you are opposed to changing the code,
and it looks kind of clumsy, so I concluded that it was not worth
trying again. Maybe I misunderstood - let me know.

Guenter
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