linux-kernel - Re: [PATCH v5 2/3] VT: Add KDFONTINFO ioctl

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Date: Thu, 25 Apr 2024 13:06:13 +0200
From: Alexey Gladkov <legion@...nel.org>
To: Helge Deller <deller@....de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>, kbd@...ts.linux.dev,
	linux-api@...r.kernel.org, linux-fbdev@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH v5 2/3] VT: Add KDFONTINFO ioctl

On Thu, Apr 25, 2024 at 12:33:28PM +0200, Helge Deller wrote:
> >>> diff --git a/include/uapi/linux/kd.h b/include/uapi/linux/kd.h
> >>> index 8ddb2219a84b..68b715ad4d5c 100644
> >>> --- a/include/uapi/linux/kd.h
> >>> +++ b/include/uapi/linux/kd.h
> >>> @@ -185,6 +185,20 @@ struct console_font {
> >>>
> >>>    #define KD_FONT_FLAG_DONT_RECALC 	1	/* Don't recalculate hw charcell size [compat] */
> >>>
> >>> +/* font information */
> >>> +
> >>> +#define KD_FONT_INFO_FLAG_LOW_SIZE	_BITUL(0) /* 256 */
> >>> +#define KD_FONT_INFO_FLAG_HIGH_SIZE	_BITUL(1) /* 512 */
> >>
> >> Do we really need those bits?
> >> You set a default min/max font size in con_font_info() above,
> >> and all drivers can override those values.
> >> So, there are always min/max sizes available.
> >
> > These bits are not about the minimum and maximum glyph size, but about the
> > number of glyphs in the font.
> >
> > Maybe this is an overkill, but sticon has this check:
> >
> > if ((w < 6) || (h < 6) || (w > 32) || (h > 32) || (vpitch != 32)
> >      || (op->charcount != 256 && op->charcount != 512))
> >
> > [ to be honest, I don’t know why this driver doesn’t accept a glyph of
> > width 4 ]
> 
> I think there was no technical limitation when I added that.
> It's just that the font would be so small...

If so, then I can remove min_height/min_width from the ioctl structure.
And most likely the flags can also be left empty since at the moment all
drivers support 512.

> > I thought it would be worth fixing the maximum number of requirements in
> > the drivers since I started adding a new ioctl.
> 
> Ok.
> 
> Helge
> 

-- 
Rgrds, legion