The goal of reserving firmware-assigned resources is to ensure that
"wildcard" resource allocation requests will not claim an address
range that is actually in use even if no attached driver is actively
using that range. However, the current approach can break in some
cases.
In particular, ACPI can enumerate devices behind PCI bridges that
don't show up in a normal PCI scan, but those device_t objects can end
up as direct children of acpi0. Reserving resources for those devices
directly from acpi0 ends up conflicting with later attempts to reserve
the PCI bridge windows.
As a workaround, defer reserving unclaimed resources until after the
initial probe and attach scan. Eventually this pass of reserving
unclaimed resources can be moved earlier, but it requires changes to
other drivers in the tree to permit enumerating devices and reserving
firmware-assigned resources in a depth-first traversal before
attaching devices whose drivers request wildcard allocations.
projects / FreeBSD / FreeBSD.git / commit