Documentation: PCI: Guide to use PCI endpoint configfs

Add Documentation to help users use PCI endpoint to configure PCI endpoint
function and to bind the endpoint function with endpoint controller.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Acked-By: Joao Pinto <jpinto@synopsys.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

2 files changed, 107 insertions, 0 deletions

diff --git a/Documentation/PCI/00-INDEX b/Documentation/PCI/00-INDEX
index ba950b296bd8..bf8223a1bf08 100644
--- a/Documentation/PCI/00-INDEX
+++ b/Documentation/PCI/00-INDEX
@@ -14,3 +14,5 @@ pcieaer-howto.txt
         - the PCI Express Advanced Error Reporting Driver Guide HOWTO
 endpoint/pci-endpoint.txt
         - guide to add endpoint controller driver and endpoint function driver.
+endpoint/pci-endpoint-cfs.txt
+        - guide to use configfs to configure the PCI endpoint function.
diff --git a/Documentation/PCI/endpoint/pci-endpoint-cfs.txt b/Documentation/PCI/endpoint/pci-endpoint-cfs.txt
new file mode 100644
index 000000000000..d740f29960a4
--- /dev/null
+++ b/Documentation/PCI/endpoint/pci-endpoint-cfs.txt
@@ -0,0 +1,105 @@
+                   CONFIGURING PCI ENDPOINT USING CONFIGFS
+                    Kishon Vijay Abraham I <kishon@ti.com>
+
+The PCI Endpoint Core exposes configfs entry (pci_ep) to configure the
+PCI endpoint function and to bind the endpoint function
+with the endpoint controller. (For introducing other mechanisms to
+configure the PCI Endpoint Function refer to [1]).
+
+*) Mounting configfs
+
+The PCI Endpoint Core layer creates pci_ep directory in the mounted configfs
+directory. configfs can be mounted using the following command.
+
+        mount -t configfs none /sys/kernel/config
+
+*) Directory Structure
+
+The pci_ep configfs has two directories at its root: controllers and
+functions. Every EPC device present in the system will have an entry in
+the *controllers* directory and and every EPF driver present in the system
+will have an entry in the *functions* directory.
+
+/sys/kernel/config/pci_ep/
+        .. controllers/
+        .. functions/
+
+*) Creating EPF Device
+
+Every registered EPF driver will be listed in controllers directory. The
+entries corresponding to EPF driver will be created by the EPF core.
+
+/sys/kernel/config/pci_ep/functions/
+        .. <EPF Driver1>/
+                ... <EPF Device 11>/
+                ... <EPF Device 21>/
+        .. <EPF Driver2>/
+                ... <EPF Device 12>/
+                ... <EPF Device 22>/
+
+In order to create a <EPF device> of the type probed by <EPF Driver>, the
+user has to create a directory inside <EPF DriverN>.
+
+Every <EPF device> directory consists of the following entries that can be
+used to configure the standard configuration header of the endpoint function.
+(These entries are created by the framework when any new <EPF Device> is
+created)
+
+        .. <EPF Driver1>/
+                ... <EPF Device 11>/
+                        ... vendorid
+                        ... deviceid
+                        ... revid
+                        ... progif_code
+                        ... subclass_code
+                        ... baseclass_code
+                        ... cache_line_size
+                        ... subsys_vendor_id
+                        ... subsys_id
+                        ... interrupt_pin
+
+*) EPC Device
+
+Every registered EPC device will be listed in controllers directory. The
+entries corresponding to EPC device will be created by the EPC core.
+
+/sys/kernel/config/pci_ep/controllers/
+        .. <EPC Device1>/
+                ... <Symlink EPF Device11>/
+                ... <Symlink EPF Device12>/
+                ... start
+        .. <EPC Device2>/
+                ... <Symlink EPF Device21>/
+                ... <Symlink EPF Device22>/
+                ... start
+
+The <EPC Device> directory will have a list of symbolic links to
+<EPF Device>. These symbolic links should be created by the user to
+represent the functions present in the endpoint device.
+
+The <EPC Device> directory will also have a *start* field. Once
+"1" is written to this field, the endpoint device will be ready to
+establish the link with the host. This is usually done after
+all the EPF devices are created and linked with the EPC device.
+
+
+                         | controllers/
+                                | <Directory: EPC name>/
+                                        | <Symbolic Link: Function>
+                                        | start
+                         | functions/
+                                | <Directory: EPF driver>/
+                                        | <Directory: EPF device>/
+                                                | vendorid
+                                                | deviceid
+                                                | revid
+                                                | progif_code
+                                                | subclass_code
+                                                | baseclass_code
+                                                | cache_line_size
+                                                | subsys_vendor_id
+                                                | subsys_id
+                                                | interrupt_pin
+                                                | function
+
+[1] -> Documentation/PCI/endpoint/pci-endpoint.txt