git: b9efaeb87a8f - main - tb_pci: Don't try to attach to PCI buses that aren't below a PCI-PCI brige

The branch main has been updated by jhb:

URL: https://cgit.FreeBSD.org/src/commit/?id=b9efaeb87a8f9cfc0cd87076a8b314785d6e04d9

commit b9efaeb87a8f9cfc0cd87076a8b314785d6e04d9
Author:     John Baldwin <jhb@FreeBSD.org>
AuthorDate: 2025-11-03 15:24:23 +0000
Commit:     John Baldwin <jhb@FreeBSD.org>
CommitDate: 2025-11-03 15:24:23 +0000

    tb_pci: Don't try to attach to PCI buses that aren't below a PCI-PCI brige
    
    This driver is a subclass of the normal PCI bus driver that is
    intended to be used for the logical child bus of a Thunderbolt PCI-PCI
    bridge device.  To determine if a given PCI bus's parent is a TB
    bridge, it examines the PCI device IDs of the parent pcibX device.
    However, this only works for pcibX devices that are actual PCI-PCI
    bridges and panics for PCI buses that are children of host bridges
    such as the pci0 child of pcib0.
    
    Probably this should not be reading device IDs (as that doesn't tell
    you if the device driver for the PCI-PCI bridge is actually a TB
    driver).  Instead, the TB PCI-PCI driver should be exporting a new
    IVAR (with a globally unique number as we do for ACPI handles) that
    returns the TB generation and the probe routine for this PCI bus
    driver should be checking for that IVAR (the way acpi_pci.c checks for
    the presence of an ACPI handle).
    
    This fixes a panic on boot if tb.ko is loaded at boot time (which the
    driver recommends for certain chipsets).
    
    Reviewed by:    imp
    Differential Revision:  https://reviews.freebsd.org/D53202
---
 sys/dev/thunderbolt/tb_pcib.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/sys/dev/thunderbolt/tb_pcib.c b/sys/dev/thunderbolt/tb_pcib.c
index 00738984ad1c..bc4fc1ce00ec 100644
--- a/sys/dev/thunderbolt/tb_pcib.c
+++ b/sys/dev/thunderbolt/tb_pcib.c
@@ -557,8 +557,20 @@ static int
 tb_pci_probe(device_t dev)
 {
 	struct tb_pcib_ident *n;
+	device_t parent;
+	devclass_t dc;
 
-	if ((n = tb_pcib_find_ident(device_get_parent(dev))) != NULL) {
+	/*
+	 * This driver is only valid if the parent device is a PCI-PCI
+	 * bridge.  To determine that, check if the grandparent is a
+	 * PCI bus.
+	 */
+	parent = device_get_parent(dev);
+	dc = device_get_devclass(device_get_parent(parent));
+	if (strcmp(devclass_get_name(dc), "pci") != 0)
+		return (ENXIO);
+
+	if ((n = tb_pcib_find_ident(parent)) != NULL) {
 		switch (n->flags & TB_GEN_MASK) {
 		case TB_GEN_TB1:
 			device_set_desc(dev, "Thunderbolt 1 Link");