[haiku] Re: Haiku for Raspberry Pi?
- From: David Given <dg@xxxxxxxxxxx>
- To: haiku@xxxxxxxxxxxxx
- Date: Sun, 29 Jan 2012 22:48:15 +0000
On 29/01/12 11:54, Miroslav Stimac wrote:
[...]
> Raspberry Pi is going to get RISC OS, too. That may be light and fast, too.
> But the GUI of the RISC OS simply looks too old fashioned
[...]
So's the insides. We know so much more about operating systems now. RISC
OS is a mess. It's grown organically with not enough oversight for too
long. For example, there's about half a platform abstraction layer, but
most code talks to hardware directly. A lot of user code runs in
supervisor mode (and while ARMs are pretty much backwards compatible in
user mode, they're *not* in supervisor mode). A lot of the APIs are
badly defined and break if you give them large addresses (due to putting
flags in the top few bits). Zero page is mapped to user processes,
because there's critical kernel variables there that need to be
accessible. There's a nasty hack in the system memory allocator to loop
up the call stack to see whether it's been called reentrantly, in order
to allow memory allocation from inside interrupt routines. And so on.
Oh, and the GUI, while brilliantly designed, is a *complete* dead loss
if you don't have a mouse. There is no accessibility.
I think Haiku for the Raspberry Pi would be a great idea --- much more
actually *useful* than RISC OS, at a fraction of the weight of Linux...
...
Incidentally, has anyone had any thoughts to porting Haiku to run on L4?
This is a tiny microkernel, covering processes and IPC and not much
more; the advantage is that it completely abstracts over the rather
hairy MMU architecture of the ARM families (which vary wildly from
processor to processor). It's used a lot in the mobile phone world for
this reason; the vendor's awful embedded OS runs as a single L4 task.
Footprint in both time and space is miniscule. If we're *just* porting
to the Raspberry Pi it's no big deal, but if we want ports to other ARM
families I reckon this would save a lot of time. There are open source
BSD versions available.
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