Re: USB device allocation

Khimenko Victor (khim@sch57.msk.ru)
Wed, 6 Oct 1999 23:12:40 +0400 (MSD)


In <37FA794F.5DA58643@transmeta.com> H. Peter Anvin (hpa@transmeta.com) wrote:
> Brian Swetland wrote:
>> >
>> > Solaris does *not* use devfs; the /devices tree is an on-disk device
>> > node tree which is constructed at initialization time, and it is
>> > persistent. A much better solution, IMNSHO.
>>
>> How exactly does such a solution work with hot-plugable devices?
>> Some daemon that gets informed of devices appearing and disappearing?
>> I don't think I'm being unreasonable in thinking that when a device
>> is added to the system it should instantly be usable. That's kind of
>> the point of dynamic busses, no?
>>

> That is one way of doing it; IMO a very good way because it lets you
> have policy in user space.

What if demon just CAN NOT get information about device appering ?
*I* know that I just inserted new zip drive and now there are few new
devices (partitions -- not all zip drives use xxx4 even if it's default :-).
Kernel knows nothing, daemon knows nothing. With devfs I just need to try
mount and devfs will try to lead appropriate driver. With your "good way" I
need to issue additional command to (re)load driver -- why such complexity is
needed ?

P.S. It's the same as kerneld/kmod: it's not really needed -- you can load
module by hand when needed. But it's convenient to have them autoloaded when
needed. The same with devfs: driver is loaded ONLY when I try to use device.
It's CAN NOT be done without virtual filesystem.

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