the mechanism of USB hotplug

[M. Warner Losh]

In message: <20051201.231433.32736713.imp at bsdimp.com>
            "M. Warner Losh" <imp at bsdimp.com> writes:
: In message: <87ab37ab0512012209j1a80a3f8l2ee36567f5fbe04e at mail.gmail.com>
:             kylin <fierykylin at gmail.com> writes:
: : sir :
: :    I am now working on the pci e hotplug of freebsd ,and reading code
: : of the relative part in linux.
: : i have never touch the field of USB .
: : now i wonder the mechanism of USB hotplug and the scsi hotplug .
: : in linux and my working on freebsd ,there r specail mechanism to
: : waiting for the hotplug event ,and the IRQ and MEM IO resource
: : allocation is complex .
: : i am fresh to the USB and the even complex SCSI driver arch , could u
: : give me some advise ?
: 
: All FreeBSD devices use devd.  Unlike Linux, FreeBSD's generic device
: architecture means that all busses automatically support hot plugging
: hooks.

I'll add that each bus just needs to implement what it needs to for
the device's arrival and departure.  See pccbb for one example.  The
allocation algorithms aren't that complex or difficult because FreeBSD
dynamically allocates all the non-wired resources.

Warner