On Tue, Oct 20, 2026 at 09:04:40AM -0500, Mario Limonciello wrote:
> Bridges that need bus reassignment are scanned in two passes. Save
> the firmware secondary bus number during the first pass, before the
> bridge is disabled, and carry it to the bus created in the second
> pass. Initialize pci_dev from this preserved bus number so drivers
> can match firmware records after PCI bus renumbering.
>
> Handle pci_alloc_dev(NULL) as well; some in-tree callers use it to
> allocate a standalone pci_dev.
>
> Signed-off-by: Mario Limonciello <[email protected]>
> ---
> drivers/pci/probe.c | 9 +++++++++
> include/linux/pci.h | 3 +++
> 2 files changed, 12 insertions(+)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 27008e2ea5afc..4ece4b70cdc15 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1012,6 +1012,7 @@ static int pci_register_host_bridge(struct
> pci_host_bridge *bridge)
> bus->sysdata = bridge->sysdata;
> bus->ops = bridge->ops;
> bus->number = bus->busn_res.start = bridge->busnr;
> + bus->initial_bus_number = bus->number;
> #ifdef CONFIG_PCI_DOMAINS_GENERIC
> if (bridge->domain_nr == PCI_DOMAIN_NR_NOT_SET)
> bus->domain_nr = pci_bus_find_domain_nr(bus, parent);
> @@ -1232,6 +1233,7 @@ static struct pci_bus *pci_alloc_child_bus(struct
> pci_bus *parent,
>
> /* Set up the primary, secondary and subordinate bus numbers */
> child->number = child->busn_res.start = busnr;
> + child->initial_bus_number = busnr;
> child->primary = parent->busn_res.start;
> child->busn_res.end = 0xff;
>
> @@ -1470,6 +1472,7 @@ static int pci_scan_bridge_extend(struct pci_bus *bus,
> struct pci_dev *dev,
> child = pci_add_new_bus(bus, dev, secondary);
> if (!child)
> goto out;
> + child->initial_bus_number = secondary;
> child->primary = primary;
> pci_bus_insert_busn_res(child, secondary, subordinate);
> child->bridge_ctl = bctl;
> @@ -1491,6 +1494,8 @@ static int pci_scan_bridge_extend(struct pci_bus *bus,
> struct pci_dev *dev,
> * do in the second pass.
> */
> if (!pass) {
> + if (!dev->initial_secondary_bus_number)
> + dev->initial_secondary_bus_number = secondary;
> if (pcibios_assign_all_busses() || broken)
>
> /*
> @@ -1526,6 +1531,9 @@ static int pci_scan_bridge_extend(struct pci_bus *bus,
> struct pci_dev *dev,
> child = pci_add_new_bus(bus, dev, next_busnr);
> if (!child)
> goto out;
> + if (dev->initial_secondary_bus_number)
> + child->initial_bus_number =
> + dev->initial_secondary_bus_number;
> pci_bus_insert_busn_res(child, next_busnr,
> bus->busn_res.end);
> }
> @@ -2508,6 +2516,7 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus)
> INIT_LIST_HEAD(&dev->bus_list);
> dev->dev.type = &pci_dev_type;
> dev->bus = pci_bus_get(bus);
> + dev->initial_bus_number = bus ? bus->initial_bus_number : 0;
> dev->driver_exclusive_resource = (struct resource) {
> .name = "PCI Exclusive",
> .start = 0,
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 5ffcf5ce8c966..f6b377dcf7a14 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -363,6 +363,8 @@ struct pci_dev {
> struct pci_slot *slot; /* Physical slot this device is in */
>
> unsigned int devfn; /* Encoded device & function index */
> + u8 initial_bus_number; /* Bus number when device was
> discovered */
> + u8 initial_secondary_bus_number; /* Bus number behind
> this bridge */
Why do we need this in the pci_dev? Is there something about
pci_scan_bridge_extend() that means it has to be in pci_dev as well as
pci_bus? Multiple copies means possible inconsistencies.
> unsigned short vendor;
> unsigned short device;
> unsigned short subsystem_vendor;
> @@ -724,6 +726,7 @@ struct pci_bus {
> struct proc_dir_entry *procdir; /* Directory entry in /proc/bus/pci */
>
> unsigned char number; /* Bus number */
> + unsigned char initial_bus_number; /* Bus number before
> reassignment */
I think it should be stylistically similar to the existing
"pci_bus.number"; adding "initial" before or after is ok, but adding
both "initial" and "bus" makes them less connected.
Users would check "vhdr->PCIBus == rdev->pdev->bus->number_initial" or
similar.
> unsigned char primary; /* Number of primary bridge */
> unsigned char max_bus_speed; /* enum pci_bus_speed */
> unsigned char cur_bus_speed; /* enum pci_bus_speed */
>
> --
> 2.43.0
>
