Linux Frame Buffer Device Development

> Nathan King wrote:
> > Hi James,
> >
> > I can mmap it, but I found that using file operations to access it was
> > about 2-3 times faster than accessing it through a mmap'ed buffer. Is
> > it possible I'm doing that wrong? Here's my stuff for that:
> >
>
> Using the file accessors are actually more portable than using mmap. And
> if it's faster, then that's better.
>
> > fbfd = open("/dev/fb0", O_RDONLY);
> > fbp = (unsigned char *)mmap(0, screensize, PROT_READ, MAP_SHARED, fbfd, 0);
> >
> > Then I read from fbp with memcpy and memcmp. If I'm going against some
> > long upheld programming convention feel free to throw things at me.
>
> Looks okay. Reading from video RAM on PCI cards will always be slower than
> writes.
>
> >
> > Thanks,
> > Nathan
> >
> >
> > Your only choices for the standard kernel are mmap and read/write. But
> if you can use an acceleration library (DirectFB http://www.directfb.org), that
> would be the best.
>
> Tony

This just occurred to me so its probably not possible, but could
something like ShadowFB for X be implemented without X?

Hi James,

I can mmap it, but I found that using file operations to access it was
about 2-3 times faster than accessing it through a mmap'ed buffer. Is
it possible I'm doing that wrong? Here's my stuff for that:

fbfd = open("/dev/fb0", O_RDONLY);
fbp = (unsigned char *)mmap(0, screensize, PROT_READ, MAP_SHARED, fbfd, 0);

Then I read from fbp with memcpy and memcmp. If I'm going against some
long upheld programming convention feel free to throw things at me.

Thanks,
Nathan


>
> On Wed, 2006-06-28 at 18:08 -0600, Nathan King wrote:
> > What's the preferred way to read a block of pixels from the screen?
> > I'm developing something like a remote desktop app, and I haven't
> > found a whole lot of documentation on this. Right now I'm opening
> > the /dev/fb0 device and accessing it by means of lseek/read, file
> > descriptor style. This seems reasonably fast but I feel there must be
> > a better way.
>
> Can you mmap /dev/fb0?
>
> Regards,
> James.

Hey folks,

What's the preferred way to read a block of pixels from the screen? I'm
developing something like a remote desktop app, and I haven't found a whole
lot of documentation on this. Right now I'm opening the /dev/fb0 device and
accessing it by means of lseek/read, file descriptor style. This seems
reasonably fast but I feel there must be a better way. I tried the XShm
memory XLib extension but that was a little slower(and a booger to get
working right). I'd rather not have to go through X anyway. Any suggestions
on where to look? Speed and hardware independence are my two biggest
priorites.

On a slightly related note, when I was screwing with XShm, I got to know a
little about shared memory functions. Can I use these on the Linux
framebuffer instead of X?

Much grass,
Nathan

Hi all,
I have a question that might be off topic but after searching the net
and mailing lists I give in and hope for some help on this list.

I wonder what the best way to mix graphics written to a framebuffer over
decoded video is. I can't change the way the graphics is written to the
device, it has to be directly to a linux framebuffer device.

My hope is that there are some generic way of doing it without bying a
fancy XYZ graphics card but if I must I'll do that.

Flow overview:
userapp -> /dev/fb1
player -> /dev/fb0
The graphics would be either with CHROMAKEY transparency 16bpp or 32 bpp
ARGB

Kind regards 
Niklas Fondberg

Hi,
  I am trying to port one of our LCD display frame
buffer driver to 2.6 kernel.
  The old 2.4 kernel had these functions defined in
fb_ops
    fb_open:    
    fb_release:
    fb_get_fix: 
    fb_get_var:     
    fb_set_var: 
    fb_get_cmap:
    fb_set_cmap: 
    fb_ioctl:   

  But the latest 2.6 fb_ops has removed these and
there is entirely new set of functions. 
  I tried to go to list archives but I could not find
information. 
  What functions in 2.6 fb_ops should to used to
implement this old 2.4 set of functions?

Regards
Syed


__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com