Re: (Semi-random) thoughts on device tree structure and devfs

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

On 07.03.10 10:43, Masao Uebayashi wrote:
> I've been spending LOTS of time to investigate various devicess sources, to
> understand some questions I've had, like:
> 
> - Why NetBSD/arm has no bus_space_mmap(4)?
> - Why tty locking is messy?
> - Why sys/dev/wscons has so many #ifdef's?  (Modular unfriendly!)
> - How dk(4) is enumerated?
> :
> 
> After absorbed myself 3 days now, I think I've figured out almost all of
> problems I've had and how I can fix these.  Before going directly to the
> answer, let me summarize problems I've found:
> 



> b) Consistent device topology management is missing
> 
> The reason why NetBSD/arm has no bus_space_mmap(9) has turned out to be the
> fact that we have no consistent (MI) way to manage physical address space of
> devices.  NetBSD/mips has a working bus_space_mmap(9) in
> sys/arch/mips/mips/bus_space_alignstride_chipdep.c.  It defines address
> windows and manage it by itself.
> 
> Who wants to reimplement it on all cpus/ports/platforms?  Considering physical
> address space is a pretty much simple concept - a single linear address space.
> And we already manage (kind of) tree of devices in autoconf(9).  Do we want
> to manage such a topology in many places?  No.

The good news:
dyoung@ and I started with prototyping pmem(9) that provides an MI
physical address space management.

The bad news:
We had no time to continue on this for more than a year now.

Christoph