[RFC] WIP: video: implement quick-n-dirty framebuffer console

[Sascha Hauer]

On Thu, Jul 09, 2015 at 12:42:54PM +0300, Antony Pavlov wrote:
> On Thu, 9 Jul 2015 08:49:20 +0200
> Sascha Hauer <s.hauer at pengutronix.de> wrote:
> 
> > Hi Antony,
> > 
> > On Wed, Jul 08, 2015 at 12:15:39PM +0300, Antony Pavlov wrote:
> > > This patch realizes very simple framebuffer console for barebox.
> > > Minimal ANSI/VT100 Escape Sequence parser is used to ignore color
> > > change commands (based on GNU screen parser).
> > > 
> > > THere are several ANSI/VT100 parsers:
> > > 
> > >   * GNU screen (git://git.savannah.gnu.org/screen.git);
> > >   * st - simple terminal (http://git.suckless.org/st);
> > >   * or even mutt (https://github.com/karelzak/mutt-kz).
> > 
> > There's even one in barebox in drivers/serial/efi-stdio.c
> > 
> > > 
> > > fbconsole mini-HOWTO
> > > ====================
> > > 
> > > 1. compile sandbox barebox with
> > > 
> > >     CONFIG_VIDEO=y
> > >     CONFIG_FBCONSOLE=y
> > >     CONFIG_DRIVER_VIDEO_SDL=y
> > > 
> > > 2. run barebox
> > > 
> > > 3. test fbconsole
> > > 
> > >     fbconsole0.active=o
> > 
> > I gave it a try on real hardware. Works nice.
> > 
> > > 
> > > TODO:
> > > 
> > >    * no visible cursor;
> > 
> > I couldn't resist and did some hacking on this. The cursor is visible
> > now. Also I implemented more control characters and color support. I'll
> > send an update patch shortly.
> > 
> > >    * FIXME: /dev/fb0 is hardcoded;
> > >    * FIXME: drop blanckchar() dirty hack;
> > >    * Sascha Hauer: character set should be prerendered for the actual framebuffer format
> > >                    before printing a string.
> > 
> > Did I mention that ealier? I don't know if that's a good idea since with
> > color support we would need quite some memory and I'm not sure if that
> > would really speed up things.
> > 
> > I'd really love to have framebuffer console in barebox. I wasn't aware
> > that this would be relatively straight forward to implement though. I'm
> > willing to help working on this job so that we finally have a fbcon.
> > 
> > Maybe one first step is to simply merge the font so that the patches
> > get smaller.
> 
> IMHO it is very reasonable to add simple tools and instruction for
> font modifing. We even can add several fonts and select one of them
> via Kconfig options as linux kernel does. There are some reasons
> for that:
> 
>    * some people prefere another fonts (e.g. Terminus);
>    * in Russia we need a font with cyrillic letters.

Ok. I'm happy to add this later, but if you want to add this from the
start, fine aswell. 

> 
> Also I prefere fix original font header file.
> Here is an example. 
> 
> 1. original font header file fragment:
> 
> +	/* 65 0x41 */
> +	0x00, /* 00000000 */
> +	0x00, /* 00000000 */
> +	0x10, /* 00010000 */
> +	0x38, /* 00111000 */
> +	0x6c, /* 01101100 */
> +	0xc6, /* 11000110 */
> +	0xc6, /* 11000110 */
> +	0xfe, /* 11111110 */
> +	0xc6, /* 11000110 */
> +	0xc6, /* 11000110 */
> +	0xc6, /* 11000110 */
> +	0xc6, /* 11000110 */
> +	0x00, /* 00000000 */
> +	0x00, /* 00000000 */
> +	0x00, /* 00000000 */
> +	0x00, /* 00000000 */
> +
> 
> 2. my version
> +	/* 65 0x41 'A' */
> +	0x00, /* ........ */
> +	0x00, /* ........ */
> +	0x10, /* ...#.... */
> +	0x38, /* ..###... */
> +	0x6c, /* .##.##.. */
> +	0xc6, /* ##...##. */
> +	0xc6, /* ##...##. */
> +	0xfe, /* #######. */
> +	0xc6, /* ##...##. */
> +	0xc6, /* ##...##. */
> +	0xc6, /* ##...##. */
> +	0xc6, /* ##...##. */
> +	0x00, /* ........ */
> +	0x00, /* ........ */
> +	0x00, /* ........ */
> +	0x00, /* ........ */

Yeah, that's much better to read.

Sascha

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