PCI: Update "pci=resource_alignment" documentation

Some uio based PCI drivers, e.g., uio_cif, do not work if the assigned PCI
memory resources are not page aligned.  By using the kernel option
"pci=resource_alignment=<align>@<bus>:<slot>.<func>" it is possible to
request page alignment for memory resources of devices.

However, this is cumbersome when using several devices, and the
bus/slot/func addresses may change if devices are added to or removed from
the system.

Extend the "pci=resource_alignment" option so we can specify the relevant
devices via PCI vendor, device, subvendor, and subdevice IDs.  The
specification of the devices via IDs is indicated by a leading string
"pci:" as argument to "pci=resource_alignment".

The format of the specification is
  pci:<vendor>:<device>[:<subvendor>:<subdevice>]

Examples:
  pci=resource_alignment=4096@pci:8086:9c22:103c:198f
  pci=resource_alignment=pci:8086:9c22       # defaults to PAGE_SIZE align

[bhelgaas: changelog, use actual vendor/device IDs in examples]
Signed-off-by: Mathias Koehrer <mathias.koehrer@etas.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 46c030a49186faabaa588afd2d284975c72c2017..a4f4d693e2c1287d533c0bc05d9f292f9b529720 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3032,6 +3032,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                                PAGE_SIZE is used as alignment.
                                PCI-PCI bridge can be specified, if resource
                                windows need to be expanded.
+                               To specify the alignment for several
+                               instances of a device, the PCI vendor,
+                               device, subvendor, and subdevice may be
+                               specified, e.g., 4096@pci:8086:9c22:103c:198f
                ecrc=           Enable/disable PCIe ECRC (transaction layer
                                end-to-end CRC checking).
                                bios: Use BIOS/firmware settings. This is the