Re: fast framebuffer reading

> 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 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?

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