Advice on Linux Framebuffer driver implemetation

Advice on Linux Framebuffer driver implemetation

[Akhilesh Soni]

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Hello,

I want advice on how to proceed for the following problem 

As per my knowledge the Linux frame buffer requires the pixel data to be in a packed pixel contiguous buffer. This means that the all the data for one pixel must be packed together, followed by the data for the next pixel, etc.(please correct me if I'm wrong)

 On my Set-top-box hardware Vulcan (IBM ppc405),  the best resolution supported  in this packed pixel format is 8bpp color table format. Vulcan resolutions above the 8bpp color table resolution  require separate  luma and chroma buffers,  where the hardware expects all the luma values to be in one buffer and all chroma values to be in another buffer. Since the data for the resolutions above 8bpp are required by the hardware to be in separate luma and chroma buffers it does not meet the LInux Frame buffer requirement of packed pixel data. 

Now how can I overcome this limitation where graphics H/W expects separate Luma and Chroma buffers whereas linux framebuffer expect all things packed. Is there any such driver already present which I can study to overcome such limitation.

I'm using Montavista linux kernel 2.4.20 on IBM stb0x25xxx(ppc405 core).

Regards,
Akhilesh 


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Re: Advice on Linux Framebuffer driver implemetation

[Carlos Munoz]

Akhilesh Soni wrote:
> Hello,
>  
> I want advice on how to proceed for the following problem
>  
> As per my knowledge the *Linux frame buffer* requires the pixel data 
> to be in a packed pixel *contiguous buffer*. This means that the all 
> the data for one pixel must be packed together, followed by the data 
> for the next pixel, etc.(please correct me if I'm wrong)
>  
>  On my Set-top-box hardware Vulcan (IBM ppc405),  the best 
> resolution supported  in this packed pixel format is 8bpp color table 
> format. Vulcan resolutions above the 8bpp color table resolution 
>  require separate  luma and chroma buffers,  where the hardware 
> expects all the luma values to be in one buffer and all chroma values 
> to be in another buffer. Since the data for the resolutions above 8bpp 
> are required by the hardware to be in separate luma and chroma buffers 
> it does not meet the LInux Frame buffer requirement of packed pixel data.
> Now how can I overcome this limitation where graphics H/W expects 
> separate Luma and Chroma buffers whereas linux framebuffer expect all 
> things packed. Is there any such driver already present which I can 
> study to overcome such limitation.
Hi Akhilesh,

I would write a new frame buffer driver for your hardware that converts 
RGB565 data (or whatever format is passed to the frame buffer) to 
luma/chroma data. There might be some open source libraries that already 
do this conversion. Writing a frame buffer driver is not very difficult.

Carlos