Responsibilty for enabling bus master enable bit?

[Richard Walter <rwalter@corp.auspex.com>]

Folks,

Following the white paper about warm reset, to prevent outstanding bus master
requests from messing up memory during system boot, system BIOSes can turn off
the bus master enable bit in all devices and the option ROM or drivers for
the devices must turn them on again.

Now, suppose that a card vendor makes a card which consists of a PCI-to-PCI
bridge and a device behind that bridge.  Who is resposible for turning on
the bus master enable bit of the bridge?  Are all bridges considered property
of the system BIOS and so it must do it?  Or, is anything on a plug-in card
considered property of the card and so the option ROM must do it?

Sincerely,
-Richard Walter
rwalter@corp.auspex.com
Note: I speak for myself, not for Auspex.