Add a new helper function for PCI devices to locate the upstream

PCI-express root port of a given PCI device.

Reviewed by:	kib, imp
MFC after:	1 week
Sponsored by:	Chelsio
Differential Revision:	https://reviews.freebsd.org/D4089

2 files changed, 14 insertions, 0 deletions

diff --git a/share/man/man9/Makefile b/share/man/man9/Makefile
index 5ae857e..b4af53d 100644
--- a/share/man/man9/Makefile
+++ b/share/man/man9/Makefile
@@ -1274,6 +1274,7 @@ MLINKS+=pci.9 pci_alloc_msi.9 \
 	pci.9 pci_find_device.9 \
 	pci.9 pci_find_extcap.9 \
 	pci.9 pci_find_htcap.9 \
+	pci.9 pci_find_pcie_root_port.9 \
 	pci.9 pci_get_max_read_req.9 \
 	pci.9 pci_get_powerstate.9 \
 	pci.9 pci_get_vpd_ident.9 \
diff --git a/share/man/man9/pci.9 b/share/man/man9/pci.9
index 2321638..4faa5f2 100644
--- a/share/man/man9/pci.9
+++ b/share/man/man9/pci.9
@@ -42,6 +42,7 @@
 .Nm pci_find_device ,
 .Nm pci_find_extcap ,
 .Nm pci_find_htcap ,
+.Nm pci_find_pcie_root_port ,
 .Nm pci_get_max_read_req ,
 .Nm pci_get_powerstate ,
 .Nm pci_get_vpd_ident ,
@@ -91,6 +92,8 @@
 .Fn pci_find_extcap "device_t dev" "int capability" "int *capreg"
 .Ft int
 .Fn pci_find_htcap "device_t dev" "int capability" "int *capreg"
+.Ft device_t
+.Fn pci_find_pcie_root_port "device_t dev"
 .Ft int
 .Fn pci_get_max_read_req "device_t dev"
 .Ft int
@@ -338,6 +341,16 @@ If the capability is not found or the device is not a HyperTransport device,
 returns an error.
 .Pp
 The
+.Fn pci_find_pcie_root_port
+function walks up the PCI device hierarchy to locate the PCI-express root
+port upstream of
+.Fa dev .
+If a root port is not found,
+.Fn pci_find_pcie_root_port
+returns
+.Dv NULL .
+.Pp
+The
 .Fn pci_get_vpd_ident
 function is used to fetch a device's Vital Product Data
 .Pq VPD