Re: 16 bit access to frame buffer
> On Wed, 18 Jun 2003, Alan Hourihane wrote: > > Use a shadow framebuffer and you only have to implement one function, which > > is how the framebuffer is refreshed. On Wed, 18 Jun 2003, Dominic Duval wrote: > Unfortunately, the piece of garbage I'm using as a display controler runs > at a very low frame > rate (in the order of 2-3 fps), so I was actually hoping to find a better > solution, so that I could benefit from the various X optimizations. > > Just refreshing the frame buffer with the content of the shadow > framebuffer will limit the performance quite a lot, considering that > the system is also pretty slow (400MHz XScale). Misleading word "refreshed". With a shadow framebuffer, the one function you would write would be given a rectangle of the shadow buffer that needed repainting, and you are expected to copy that rectangle into the real framebuffer. I don't remember the details, but this will be called when the server thinks a group of drawing commands have been collected, but often enough that video refreshes wont be missed. You shouldn't find that it is trying to draw into the same rectangles many time in a single refresh, so (IIRC) for a 400MHz Pentium and a graphics card with slow memory (say an ISA VGA card from the days when 256 color VGA was a big deal), displaying at say 60Hz refresh, you would find that using a shadow framebuffer was faster than writing directly to the card. -- Andrew C Aitchison ___ Devel mailing list [EMAIL PROTECTED] http://XFree86.Org/mailman/listinfo/devel
Re: 16 bit access to frame buffer
Unfortunately, the piece of garbage I'm using as a display controler runs at a very low frame rate (in the order of 2-3 fps), so I was actually hoping to find a better solution, so that I could benefit from the various X optimizations. Just refreshing the frame buffer with the content of the shadow framebuffer will limit the performance quite a lot, considering that the system is also pretty slow (400MHz XScale). Thanks, -Dominic On Wed, 18 Jun 2003, Alan Hourihane wrote: > Use a shadow framebuffer and you only have to implement one function, which > is how the framebuffer is refreshed. > > Alan. > ___ > Devel mailing list > [EMAIL PROTECTED] > http://XFree86.Org/mailman/listinfo/devel > ___ Devel mailing list [EMAIL PROTECTED] http://XFree86.Org/mailman/listinfo/devel
Re: 16 bit access to frame buffer
On Wed, Jun 18, 2003 at 03:54:46PM -0400, Dominic Duval wrote: > Hello, > > I'm currently trying to configure X for a frame buffer device which can > _only_ be accessed in 16-bit. It's a long story, but accessing the frame > buffer memory in 8 or 32 bits is just not possible with our current > hardware. > > The way I understand it, X mmaps() the /dev/fb0 device and makes 32-bit > write accesses to this memory area afterwards. Before I jump in the code > and try to modify every single write access to the memory mapped area, I'd like > to know if there's an easy way to do this and/or if something similar has > been done before. > > I haven't spent a lot of time inspecting the code, so any pointer as to > where I might need to focus my efforts will be well appreciated. Use a shadow framebuffer and you only have to implement one function, which is how the framebuffer is refreshed. Alan. ___ Devel mailing list [EMAIL PROTECTED] http://XFree86.Org/mailman/listinfo/devel
16 bit access to frame buffer
Hello, I'm currently trying to configure X for a frame buffer device which can _only_ be accessed in 16-bit. It's a long story, but accessing the frame buffer memory in 8 or 32 bits is just not possible with our current hardware. The way I understand it, X mmaps() the /dev/fb0 device and makes 32-bit write accesses to this memory area afterwards. Before I jump in the code and try to modify every single write access to the memory mapped area, I'd like to know if there's an easy way to do this and/or if something similar has been done before. I haven't spent a lot of time inspecting the code, so any pointer as to where I might need to focus my efforts will be well appreciated. Cheers, Dominic Duval ___ Devel mailing list [EMAIL PROTECTED] http://XFree86.Org/mailman/listinfo/devel
