linux-kernel - Re: [PATCH] console ASCII glyph 1:1 mapping

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Message-ID: <alpine.LFD.2.00.0812110823320.3340@localhost.localdomain>
Date:	Thu, 11 Dec 2008 08:25:09 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Brueckl <ib@...peronline.de>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] console ASCII glyph 1:1 mapping


Hmm. I bounced both your patches to Peter, since they look valid but I 
want somebody who knows this code better to ack them. 

Peter - is there somebody else who should double-check these things, or 
can you ack them?

		Linus

On Wed, 10 Dec 2008, Ingo Brueckl wrote:
>
> For the console, there is a 1:1 mapping of glyphs which cannot be found 
> in the current font. This seems to be meant as a kind of 'emergency 
> fallback' for fonts without unicode mapping which otherwise would 
> display nothing readable on the screen.
> 
> At the moment it affects all chars for which no substitution character 
> is defined. In particular this means that for all chars (>= 128) where 
> there is no iso88591-1/unicode character (e.g. control character area) 
> you'll get the very strange 1:1 mapping of the (cp437) graphics card 
> glyphs.
> 
> I'm pretty sure that the 1:1 mapping should only affect strict ASCII 
> code characters, i.e. chars < 128.
> 
> The patch limits the mapping as it probably was meant anyway.
> 
> Signed-off-by: Ingo Brueckl <ib@...peronline.de>
> 
> --- linux-2.6.27.8.orig/drivers/char/vt.c	2008-12-05 21:03:02.000000000 +0100
> +++ linux-2.6.27.8/drivers/char/vt.c	2008-12-10 20:51:30.000000000 +0100
> @@ -2287,7 +2287,7 @@ rescan_last_byte:
>  				    continue; /* nothing to display */
>  				}
>  				/* Glyph not found */
> -				if ((!(vc->vc_utf && !vc->vc_disp_ctrl) || c < 128) && !(c & ~charmask)) {
> +				if ((!(vc->vc_utf && !vc->vc_disp_ctrl) && c < 128) && !(c & ~charmask)) {
>  				    /* In legacy mode use the glyph we get by a 1:1 mapping.
>  				       This would make absolutely no sense with Unicode in mind,
>  				       but do this for ASCII characters since a font may lack
> 
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