[TUHS] Re: Origins of the frame buffer device

[Paul Ruizendaal via TUHS <tuhs@tuhs.org>]

Thanks for this.

My question was unclear: I wasn't thinking of the hardware, but of the software abstraction, i.e. the device files living in /dev

I’ve now read through SunOS man pages and it would seem that the /dev/fb file was indeed similar to /dev/fbdev on Linux 15 years later. Not quite the same though, as initially it seems to have been tied to the kernel part of the SunWindows software. My understanding of the latter is still limited though. The later Linux usage is designed around mmap() and I am not sure when that arrived in SunOS (the mmap call exists in the manpages of 4.2BSD, but was not implemented at that time). Maybe at the time of the Sun-1 and Sun-2 it worked differently.

The frame buffer hardware is exposed differently in Plan9. Here there are device files (initially /dev/bit/screen and /dev/bit/bitblt) but these are not designed around mmap(), which does not exist on Plan9 by design. It later develops into the /dev/draw/... files. However, my understanding of graphics in Plan9 is also still limited.

All in all, finding a conceptually clean but still performant way to expose the frame buffer (and acceleration) hardware seems to have been a hard problem. Arguably it still is.



> On 5 Mar 2023, at 19:25, Kenneth Goodwin <kennethgoodwin56@gmail.com> wrote:
> 
> The first frame buffers from Evans and Sutherland were at University of Utah, DOD SITES and NYIT CGL as I recall.
> 
> Circa 1974 to 1978.
> 
> They were 19 inch RETMA racks.
> Took three to get decent RGB.
> 
> 8 bits per pixel per FB.
> 
> On Sun, Mar 5, 2023, 10:02 AM Paul Ruizendaal via TUHS <tuhs@tuhs.org> wrote:
> I am confused on the history of the frame buffer device.
> 
> On Linux, it seems that /dev/fbdev originated in 1999 from work done by  Martin Schaller and  Geert Uytterhoeven (and some input from Fabrice Bellard?).
> 
> However, it would seem at first glance that early SunOS also had a frame buffer device (/dev/cgoneX. /dev/bwoneX, etc.) which was similar in nature (a character device that could be mmap’ed to give access to the hardware frame buffer, and ioctl’s to probe and configure the hardware). Is that correct, or were these entirely different in nature?
> 
> Paul
>