[parisc-linux] XFree status

[Alan Cox]

> Alan Cox wrote:
> > I have a server linked.
> Alan - that's Cool! Wow!

Its still got its atoms in a twist, so its bombing out in Xnest loading the
first font.

> > inb/inw/outb/outw and friends are right now null
> > functions until I fill them in. Thats not a big deal. Initially I'll probably
> > use /dev/port but for speed I hope everyone uses mmio based hardware.
> 
> All HP graphics for PARISC are memory mapped. Both "GSC" and PCI flavors.

Yes, but if I want to say put an S3 Trio64 in my A180 and a USB card for
keyboard mouse..,, (and yes these are sitting on my desk)

> But I'm pretty clueless how linux X server finds/talks to a frame buffer.
> For HPUX, the graphics driver supports some ioctl()'s.
> Any references to describe how it works for linux?

The OS specific X code in XFree86 knows several ways to talk to Linux

Memory:

1.	Directly mmap()ing /dev/mem or /dev/kmem to get access to the 
	mmio space of the card and frame buffer memory. 

2.	Mapping the pci space via a kernel frame buffer device (/dev/fb*)

3.	Arbitary other mmap based code that you plug into it (harder to do)


I/O

1.	Use of iopl/ioperm on x86

2.	Use of mmap to map the PCI I/O space regions on different 
	platforms (which doesnt work on some PA kit)

3.	Arbitary other code we plug into it 


For I/O it seems that on things like the A180 the only way to do it is to use
/dev/port and pread/pwrite the file handle for each port I/O. This is slow but
hopefully primarily used for booting the card (XFree 4.0 has a X86 emulator
for booting the BIOS firmware on PCI cards)


For most machines I imagine we would be using mmio and the /dev/fb interface.

Alan