Re: drivers for l4-hurd

[Jörg Sonnenberger]

On Fri, 29 Nov 2002 11:58:58 +0100
Jörg Sonnenberger <address@hidden> wrote:

> On Thu, 28 Nov 2002 23:46:03 +0100
> address@hidden (Peter 'p2' De Schrijver) wrote:
> [snip]
> > > > > In fact, I would think that for some things (Bus driver + device 
> > > > > drivers)
> > > > > it's easier to have it all in one driver program with maybe 
> > > > > dynamically
> > > > > loadable shared object modules.
> > > > > 
> > > > 
> > > > This split depends on a few things : speed of L4 messaging and memory
> > > > mapping, device throughput, CPU speed, ... . 
> > > 
> > > Oh, yes, I don't want to give a premature answer.  As repeatably said, my
> > > message is that an answer should not be given now ;)
> > > 
> > 
> > The API's should probably be designed so that drivers can share an AS or
> > live in a different AS. This would allow us to use seperate AS's when
> > developing/testing and move to 1 AS when speed is required.
> 
> First of all the problem with bus driver and device driver is the dependency 
> of
> IDE on PCI, of SCSI on PCI, of USB on PCI. You got the point. The solution 
> with
> shared AS sounds partly reasonable. I don't think all device drivers using 
> PCI should
> shared AS, but they could embed the PCI bus driver AS and some memory for IO 
> messages.
> This would give good performance and isolate the drivers. The AS of the bus 
> driver
> should be r/o of course (with the above exception).

One more thought: It could be done the other, too. E.g. to embed the AS of all
device drivers in the AS of the bus driver. This is based on the assumption
that IPC from the bus driver to the device driver has short argument list, while
IPC from device driver to bus driver can transfer large command message.
I don't know if this assumption is true.

-- Joerg Sonnenberger

> 
> -- Joerg Sonnenberger
> 
> > 
> > Cheers,
> > 
> > Peter.
> > 
> > 
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> > 
> 
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