pci: Export bus numbers for bridge devices in struct pci_conf

This exports bus information about bridges to userspace via the
less-privileged PCIOCGETCONF ioctl.  Previously if userspace wished to
query this information, it had to use direct PCI config register
access which requires higher privilege.

Reviewed by:	imp
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D55771

4 files changed, 43 insertions, 2 deletions

diff --git a/share/man/man4/pci.4 b/share/man/man4/pci.4
index f5d42efb4f37..38a427e64f4f 100644
--- a/share/man/man4/pci.4
+++ b/share/man/man4/pci.4
@@ -244,6 +244,12 @@ structure.
 This should always be equivalent to the offset of the
 .Va pc_spare
 member.
+.It pc_secbus
+Secondary PCI bus number.
+.Pq Only valid for bridge devices
+.It pc_subbus
+Subordinate PCI bus number.
+.Pq Only valid for bridge devices
 .It pc_spare
 Reserved for future use.
 .El
diff --git a/sys/dev/pci/pci.c b/sys/dev/pci/pci.c
index a46813cc155a..0dddd2dd263f 100644
--- a/sys/dev/pci/pci.c
+++ b/sys/dev/pci/pci.c
@@ -798,6 +798,9 @@ pci_fill_devinfo(device_t pcib, device_t bus, int d, int b, int s, int f,
 	devlist_entry->conf.pc_progif = cfg->progif;
 	devlist_entry->conf.pc_revid = cfg->revid;
 
+	devlist_entry->conf.pc_secbus = cfg->bridge.br_secbus;
+	devlist_entry->conf.pc_subbus = cfg->bridge.br_subbus;
+
 	pci_numdevs++;
 	pci_generation++;
 
diff --git a/sys/dev/pci/pci_user.c b/sys/dev/pci/pci_user.c
index 9768030995e7..0e23363fba73 100644
--- a/sys/dev/pci/pci_user.c
+++ b/sys/dev/pci/pci_user.c
@@ -81,7 +81,9 @@ struct pci_conf32 {
 	u_int32_t	pd_unit;	/* device unit number */
 	int		pd_numa_domain;	/* device NUMA domain */
 	u_int32_t	pc_reported_len;/* length of PCI data reported */
-	char		pc_spare[64];	/* space for future fields */
+	uint8_t		pc_secbus;	/* secondary bus number */
+	uint8_t		pc_subbus;	/* subordinate bus number */
+	char		pc_spare[62];	/* space for future fields */
 };
 
 struct pci_match_conf32 {
@@ -889,6 +891,8 @@ pci_conf_for_copyout(const struct pci_conf *pcp, union pci_conf_union *pcup,
 		pcup->pc32.pd_unit = (uint32_t)pcp->pd_unit;
 		if (cmd == PCIOCGETCONF32) {
 			pcup->pc32.pd_numa_domain = pcp->pd_numa_domain;
+			pcup->pc32.pc_secbus = pcp->pc_secbus;
+			pcup->pc32.pc_subbus = pcp->pc_subbus;
 			pcup->pc32.pc_reported_len =
 			    (uint32_t)offsetof(struct pci_conf32, pc_spare);
 		}
@@ -1315,6 +1319,32 @@ pci_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int flag, struct thread *t
 			else
 				dinfo->conf.pd_numa_domain = 0;
 
+			if (dinfo->cfg.dev != NULL) {
+				/*
+				 * Re-read the values in case a driver
+				 * changed them after the device was
+				 * initially scanned.
+				 */
+				switch (dinfo->conf.pc_hdr) {
+				case PCIM_HDRTYPE_BRIDGE:
+					dinfo->conf.pc_secbus =
+					    pci_read_config(dinfo->cfg.dev,
+						PCIR_SECBUS_1, 1);
+					dinfo->conf.pc_subbus =
+					    pci_read_config(dinfo->cfg.dev,
+						PCIR_SUBBUS_1, 1);
+					break;
+				case PCIM_HDRTYPE_CARDBUS:
+					dinfo->conf.pc_secbus =
+					    pci_read_config(dinfo->cfg.dev,
+						PCIR_SECBUS_2, 1);
+					dinfo->conf.pc_subbus =
+					    pci_read_config(dinfo->cfg.dev,
+						PCIR_SUBBUS_2, 1);
+					break;
+				}
+			}
+
 			if (pattern_buf == NULL ||
 			    pci_conf_match(cmd, pattern_buf, num_patterns,
 			    &dinfo->conf) == 0) {
diff --git a/sys/sys/pciio.h b/sys/sys/pciio.h
index 64c0b32cb8e2..58928544f171 100644
--- a/sys/sys/pciio.h
+++ b/sys/sys/pciio.h
@@ -79,7 +79,9 @@ struct pci_conf {
 	u_long		pd_unit;	/* device unit number */
 	int		pd_numa_domain;	/* device NUMA domain */
 	size_t		pc_reported_len;/* length of PCI data reported */
-	char		pc_spare[64];	/* space for future fields */
+	uint8_t		pc_secbus;	/* secondary bus number */
+	uint8_t		pc_subbus;	/* subordinate bus number */
+	char		pc_spare[62];	/* space for future fields */
 };
 
 struct pci_match_conf {