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  From: Marcus Sundberg <mackan@stacken.kth.se>
  To  : ggi-develop@eskimo.com
  Date: Sun, 16 May 1999 15:42:34 +0000

Re: Using Directbuffer write pointer in kernel

Gernot Ziegler wrote:
> I am just trying to improve my tool application for a video card with GGI
> DirectBuffer:
> I would like to pass the DirectBuffer->write address to a kernel module,
> which then writes it to my PCI video card, which in its turn writes the
> digitized video signal to my graphics card (Complicated sentence, I know
> ;) ).
>
> But the address I get from DirectBuffer seems to be a userspace address,
> and this is nothing the kernel module can write directly to the video
> hardware.
>
> I suspect this has something to do with userspace->kernel space
> conversion, but I have no clue about these things  - is there any
> possibility to realize this conversion, either in the user space program
> or in the kernel module ?

Hi,

DirectBuffer->write is not a pointer to your graphics card memory.
It's a pointer into a LibGGI application's address space, which is
completely unrelated to the hardware you have in the machine.

What you need is a kernel driver for your graphics card and a kernel
driver for the video card, and then you need them to cooperate to
achieve what you want.

//Marcus
-- 
-------------------------------+------------------------------------
        Marcus Sundberg        | http://www.stacken.kth.se/~mackan/
 Royal Institute of Technology |       Phone: +46 707 295404
       Stockholm, Sweden       |   E-Mail: mackan@stacken.kth.se

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