[LinuxBIOS] Programming i2c video-out

joe at smittys.pointclark.net joe at smittys.pointclark.net
Tue Mar 13 05:57:27 CET 2007

Quoting Luc Verhaegen <libv at skynet.be>:

> 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.
> http://unichrome.sf.net/

I understand video encoders are not standalone. They receive input  
from your GPU, in my case it is embedded so the northbridge, encode  
it, and send it out the output. I have a vga bios that outputs to  
DVOA. This is the the port that is connected to the input of the video  
encoder. Unfortunatly (intel) never released a module for this video  
encoder. So, this is what I want to do. Write a driver to initialize  
the video encoder and then when the vga bios starts outputting to DVOA  
we should have signal correct?

Thanks - Joe

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