[LinuxBIOS] Programming i2c video-out

Luc Verhaegen libv at skynet.be
Tue Mar 13 05:19:04 CET 2007

On Tue, Mar 13, 2007 at 04:50:47AM +0100, Quux wrote:
> hey Joe,
> I'd guess, during testing, the sequence would make not much difference.
> Once the code is working, the earlier it gets called, the more you could
> output onto TV which would be desirable. maybe use it as debug output
> device.   greetinx: --Q
> joe at smittys.pointclark.net schrieb:
> > Hello,
> > I have a question. I see in the sources there are drivers for i2c  
> > devices. What I am thinking is to write a driver to program and  
> > initialize the tv-out chip through the i2c (smbus). The tv-out chip is  
> > embedded in the board and programable through i2c. If this is possible  
> > I would need to know at what point the video bios gets initialized.  
> > And I would want to load this driver right after video bios gets  
> > initialized correct? Thoughts?
TV encoders are not standalone devices. They get pixel data from your 
graphics device, and they either provide or receive sync signals, 
blanking and clocking either to or from the graphics device. It doesn't 
matter if these devices are programmed over smbus or over graphics 
device local I2C/GPIO lines.

So this is an integral part part of graphics device initialisation. 
As such, it is all up to the VGA BIOS, or, if available, up to the 
direct support of certain graphics devices.

Luc Verhaegen.

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