Re: misc questions about the device&driver arch

still a question about newbus 's BUS interface :
usage of DEVICE_IDENTIFY AND BUS_ADD_CHILD
I know these bus interface func r called accessor functions ,that call
the appropriate function by checking the parameter.just like the
polymorphism technic in OOP . that's really a magic :)
my first QUESTION is what if the calling device do not realize the
corresponding interface ? taking bus_add_child interface as example.
only a few device-drivers have implement it ,but more r called for it
.what will happen when BUS_ADD_CHILD(device_t bus, int order, const
char *name, int unit) 's bus do not implement it ?

The BUS_ADD_CHILD interface is called by the bus. Children drivers
don't need to know/care about it. They aren't always needed,
however. You'll likely find that only busses that are not
self-enumerating have these registered. This is so that when the
identiy routines are called to enumerate the children otherwise
unknown to the parent bus, the parent bus gets notification of the
addition of these new chilren.

my second is :a driver's DEVICE_IDENTIFY always call its device 's
parent's BUS_ADD_CHILD ,what is the semantic of them:)
thank u

nope. It may be called once per bus instance per driver, if the bus
is not self-identifying. If the bus is self-idntiying, chances are
that it will not be called. pci never calls its children drivers'
identify routine because it already knows all the children on the bus
and doesn't need the leaf drivers to go find instances of themselves.
the isa bus driver, on the other hand, does call the identify routine
so that pre-plug and play standard device enumeration can happen.

Warner


the drivers who have registered the bus_add_child (not too many)
Acpi.c (dev\acpica): DEVMETHOD(bus_add_child, acpi_add_child),
Atkbdc_isa.c (isa): DEVMETHOD(bus_add_child, atkbdc_add_child),
Canbus.c (pc98\pc98): DEVMETHOD(bus_add_child, canbus_add_child),
Firewire.c (dev\firewire): DEVMETHOD(bus_add_child, firewire_add_child),
Fwohci_pci.c (dev\firewire): DEVMETHOD(bus_add_child, fwohci_pci_add_child),
Iicbus.c (dev\iicbus): DEVMETHOD(bus_add_child, iicbus_add_child),
Isa_common.c (isa): DEVMETHOD(bus_add_child, isa_add_child),
Legacy.c (amd64\amd64): DEVMETHOD(bus_add_child, legacy_add_child),
Legacy.c (i386\i386): DEVMETHOD(bus_add_child, legacy_add_child),
Nexus.c (amd64\amd64): DEVMETHOD(bus_add_child, nexus_add_child),
Nexus.c (i386\i386): DEVMETHOD(bus_add_child, nexus_add_child),
Nexus.c (ia64\ia64): DEVMETHOD(bus_add_child, nexus_add_child),
Ppbconf.c (dev\ppbus): DEVMETHOD(bus_add_child, ppbus_add_child),
Smbus.c (dev\smbus): DEVMETHOD(bus_add_child, smbus_add_child),


On 5/20/06, Warner Losh <imp@xxxxxxxxxx> wrote:
From: "william wallace" <avalonwallace@xxxxxxxxx>
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).

Warner

On 5/20/06, Warner Losh <imp@xxxxxxxxxx> 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



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we who r about to die,salute u!


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