misc questions about the device&driver arch

Warner Losh imp at bsdimp.com
Sat May 20 00:37:10 PDT 2006

From: "william wallace" <avalonwallace at gmail.com>
Subject: Re: misc questions about the device&driver arch
Date: Sat, 20 May 2006 13:39:08 +0800

> comparing the method array of pci_pci and cardbusbridge:
> what losts in pci bridge but exist in cardbusbridge:
> 1 card interface
> 2 power interface
> 3 some functions :
>   3ain bus interface
> 	(bus_driver_added,		cbb_driver_added),
> 	(bus_child_detached,		cbb_child_detached),
> 	(bus_child_present,		cbb_child_present),
>  3b in device interface
> 	(device_detach,		cbb_detach),
> what exists in pci bridge but losts in cardbusbridge:
>  (pcib_route_interrupt,	pcib_route_interrupt),
> not only that ,functions r very different eventhough they realize the
> same interface function template
> wooo,so long to go to hotplug pci

Yes.  The hardest part would be to create a pci hot swap bridge
driver.  The interface for them tend to be underdocumented.

The bus_child_present is important for detaching.

Also, I think that we may need to start implementing a quiess method
to tell the drivers they are about to be removed.   For hot plug PCI,
the model is that you quess the driver, the os tells you somehow it is
safe, and then you remove the card.  The details vary (some system are
all in software, while others have a complicated interlock and LEDs),
but they are similar.  Cardbus is harder in some ways because cards
leave unannounced (in fact, there's not a good way to announce a card
leaving, but there should be).


> On 5/20/06, Warner Losh <imp at bsdimp.com> wrote:
> > Busses create devices to represent hardware in the system.  The bus
> > then causes these devices to be probed and attached.  This latter
> > usage is for those cases.  As drivers are loaded these devices are
> > offered to the new (and old) drivers in the system.
> >
> > FreeBSD inherently dynamic in its device system.  The hardest part of
> > adding hotplug support is programming the bridge.  Adding new devices
> > to the tree is easy, but knowing when to add them is hard since you
> > have to write a bridge driver...
> >
> > Warner
> >
> -- 
> we who r about to die,salute u!

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