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Date: Thu, 05 Apr 2007 16:13:36 -0700
From: Carlos Munoz <carlos@kenati.com>
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To: Akhilesh Soni <akhilesh@innomedia.soft.net>
Subject: Re: Advice on Linux Framebuffer driver implemetation
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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