RE: [PATCH v2 1/3] PCI: Preserve the initial bus number in pci_dev

[Deucher, Alexander]

Public

> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@xxxxxxx>
> Sent: Tuesday, October 20, 2026 10:05 AM
> To: Bjorn Helgaas <helgaas@xxxxxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Koenig, Christian
> <Christian.Koenig@xxxxxxx>
> Cc: Oz Tiram <oz@xxxxxxxxxxxxxxxxxx>; linux-pci@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; amd-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-
> devel@xxxxxxxxxxxxxxxxxxxxx; Limonciello, Mario
> <Mario.Limonciello@xxxxxxx>
> Subject: [PATCH v2 1/3] PCI: Preserve the initial bus number in pci_dev
>
> 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 <mario.limonciello@xxxxxxx>

Looks good to me.  Patch 1 is:
Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>

Patches 2, 3:
Reviewed-by: Alex Deucher <alexander.deucher@xxxxxxx>

I don't have a preference which tree these go through, assuming Bjorn is ok with the PCI change.

Alex

> ---
>  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 */
>       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 */
>       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