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

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Date:   Thu, 19 Jan 2023 15:55:24 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Alexey Gladkov <legion@...nel.org>
Cc:     Samuel Thibault <samuel.thibault@...-lyon.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

On Sun, Dec 18, 2022 at 04:38:33PM +0100, Alexey Gladkov wrote:
> On Sun, Dec 18, 2022 at 04:28:57PM +0100, Samuel Thibault wrote:
> > 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.
> 
> Yeah, but I thought that since someone decided to touch this old code,
> then this someone will improve this old limit :)

That's fine, but it would be a separate change, not this one.

thanks,

greg k-h