linux-kernel - Re: [kbd] [patchv2 3/3] VT: Bump font size limitation to 64x128 pixels

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Message-ID: <20221218152857.qle75c6lhexkdoym@begin>
Date:   Sun, 18 Dec 2022 16:28:57 +0100
From:   Samuel Thibault <samuel.thibault@...-lyon.org>
To:     Alexey Gladkov <legion@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, kbd@...ts.altlinux.org,
        linux-kernel@...r.kernel.org
Subject: Re: [kbd] [patchv2 3/3] VT: Bump font size limitation to 64x128
 pixels

Alexey Gladkov, le dim. 18 déc. 2022 16:25:01 +0100, a ecrit:
> On Sun, Dec 18, 2022 at 03:55:32PM +0100, Samuel Thibault wrote:
> > Alexey Gladkov, le dim. 18 déc. 2022 15:39:38 +0100, a ecrit:
> > > On Sun, Dec 18, 2022 at 01:32:12AM +0100, Samuel Thibault wrote:
> > > > -#define max_font_size 65536
> > > > +#define max_font_width	64
> > > > +#define max_font_height	128
> > > > +#define max_font_glyphs	512
> > > > +#define max_font_size	(max_font_glyphs*max_font_width*max_font_height)
> > > 
> > > As a suggestion that you can safely ignore. Maybe make max_font_glyphs a
> > > sysctl parameter to be able to use larger fonts ?
> > > 
> > > I get requests from time to time in kbd that it is not possible to load a
> > > larger font.
> > 
> > 64KiB was really low, while the theoretically possible max was
> > 32*32*512 = 512KB, so I understand there used to be such requests :)
> > 
> > Here, by setting the max to 64x128*512, I don't think we'll need more.
> 
> I was not talking about the size of one glyph, but about the number of
> glyphs in the font. Right now the font cannot have more than 512 glyphs.

That one is unfortunately *very* hardcoded in the VT code, since it's
the very representation of the console text in vc_screenbuf which is set
to the VGA-based 16bits per glyph, with a 8+8 or 9+7 separation between
glyph number and color number. Lifting that would be way more involved.

Samuel