Virtual framebuffer driver - mmap problem

Virtual framebuffer driver - mmap problem

[Shivappa Kushtagi]

Hi,

I would like to use virtual framebuffer on a linux system which is
installed with R.H.9 to simulate my target display ( an embedded
device with 320*480 resolution).

I have booted the system with VFB enabled. I verified it by checking
the file /proc/fb

# more /proc/fb
0 Virtual FB
1 VESA VGA

Problem :

I have written a application which will mmap /dev/fb0 and fill it with
some RGB values. I run framebuffer based VNC server to see whatever I
have written. I always get a white image. Looks like mmap is mapped to
some other address and fbvnc server is reading from somewhere else.

Does the existing drivers/video/vfb.c code works ? or Do I need to
tweak it ?


Regards
Shivappa


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Re: Virtual framebuffer driver - mmap problem

[Geert Uytterhoeven]

On Wed, 8 Sep 2004, Shivappa Kushtagi wrote:
> I would like to use virtual framebuffer on a linux system which is
> installed with R.H.9 to simulate my target display ( an embedded
> device with 320*480 resolution).

The virtual framebuffer is intended for testing _the kernel_ only.

> I have written a application which will mmap /dev/fb0 and fill it with
> some RGB values. I run framebuffer based VNC server to see whatever I
> have written. I always get a white image. Looks like mmap is mapped to
> some other address and fbvnc server is reading from somewhere else.
>
> Does the existing drivers/video/vfb.c code works ? or Do I need to
> tweak it ?

You cannot mmap() the video memory of vfb.

Why don't you use vesafb?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds


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Re: Virtual framebuffer driver - mmap problem

[Shivappa Kushtagi]

> I would like to use virtual framebuffer on a linux system which is
> installed with R.H.9 to simulate my target display ( an embedded
> device with 320*480 resolution).

== The virtual framebuffer is intended for testing _the kernel_ only.

> I have written a application which will mmap /dev/fb0 and fill it with
> some RGB values. I run framebuffer based VNC server to see whatever I
> have written. I always get a white image. Looks like mmap is mapped to
> some other address and fbvnc server is reading from somewhere else.
>
> Does the existing drivers/video/vfb.c code works ? or Do I need to
> tweak it ?

== You cannot mmap() the video memory of vfb.

==  Why don"t you use vesafb?

As I had mentioned in my earlier post, I wanted to use virtual
framebuffer to simulate the display of my target device (say some PDA
with size 320*480 ).  With vesafb, I will not be able to change the
resolution ( fbset fails telling,  invalid argument )


Is there any other framebuffer based methods to simulate a display ?

Regards
Shivappa


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