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Re: SVGA console

From: Peter 'p2' De Schrijver
Subject: Re: SVGA console
Date: Sun, 17 Aug 2003 23:00:40 +0200
User-agent: Mutt/1.5.4i

On Sun, Aug 17, 2003 at 04:55:00PM +0200, Niels M?ller wrote:
> Marco Gerards <metgerards@student.han.nl> writes:
> > For better VGA support I want to add some features. First I'd like to
> > add modeline support. This is how SVGATextMode, Xfree, svgalib,
> > etc. setup a videomode. This is really easy to do, actually I already
> > have most code to configure the hardware.
> I think modelines aren't well suited to humans, so they should
> probably be hidden somewhere within the driver.
> For configuration, it makes more sense to specify the resolution
> (either in rows, columns and character size, or directly in pixels),
> desired vertical update rate (frame rate), *optional* tweaks for the
> precise timing for syncing, vertical and horisontal blanking etc. And
> then let the driver calculate the appropriate figures for the
> hardware.

This is not always possible. The timings depend on the monitor connected
to the graphics card. So you need a way to figure those out. Modern
monitors might support DDC which allows you to query the monitor for
modes. DDC however is only available if you use the HD15 VGA connector.
There are also VESA standard timings which most PC monitors probably support. 
Fixed frequency sun/sgi/... monitors probably don't support those. This
is only for the PC platform. Macs used to have another autodetection
scheme with other standard timings and resolutions.

We should probably start by defining a common naming scheme for video
modes. The user can then just specify a name and the console can fetch
it from a local monitor config file, a global config file containing
standard timings or DDC (or some other autoconfig mechanism).

I much more like the modefile format used by fbset than the one used by
xfree,svgalib etc. It's much easier to understand and maps better with
the actual hw. The xfree format is basically a dump of the timing
registers of a VGA compatible chip.



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