PCI: SRIOV control and status via sysfs (documentation)

Add documentation of new sysfs files and new pci_driver SRIOV
configuration interface.

[bhelgaas: changelog]
Signed-off: Donald Dutile <ddutile@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index dff1f48..1ce5ae3 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -222,3 +222,37 @@ Description:
 		satisfied too.  Reading this attribute will show the current
 		value of d3cold_allowed bit.  Writing this attribute will set
 		the value of d3cold_allowed bit.
+
+What:		/sys/bus/pci/devices/.../sriov_totalvfs
+Date:		November 2012
+Contact:	Donald Dutile <ddutile@redhat.com>
+Description:
+		This file appears when a physical PCIe device supports SR-IOV.
+		Userspace applications can read this file to determine the
+		maximum number of Virtual Functions (VFs) a PCIe physical
+		function (PF) can support. Typically, this is the value reported
+		in the PF's SR-IOV extended capability structure's TotalVFs
+		element.  Drivers have the ability at probe time to reduce the
+		value read from this file via the pci_sriov_set_totalvfs()
+		function.
+
+What:		/sys/bus/pci/devices/.../sriov_numvfs
+Date:		November 2012
+Contact:	Donald Dutile <ddutile@redhat.com>
+Description:
+		This file appears when a physical PCIe device supports SR-IOV.
+		Userspace applications can read and write to this file to
+		determine and control the enablement or disablement of Virtual
+		Functions (VFs) on the physical function (PF). A read of this
+		file will return the number of VFs that are enabled on this PF.
+		A number written to this file will enable the specified
+		number of VFs. A userspace application would typically read the
+		file and check that the value is zero, and then write the number
+		of VFs that should be enabled on the PF; the value written
+		should be less than or equal to the value in the sriov_totalvfs
+		file. A userspace application wanting to disable the VFs would
+		write a zero to this file. The core ensures that valid values
+		are written to this file, and returns errors when values are not
+		valid.  For example, writing a 2 to this file when sriov_numvfs
+		is not 0 and not 2 already will return an error. Writing a 10
+		when the value of sriov_totalvfs is 8 will return an error.