Kernel-4.18.0-80.el8_pci-endpoint-cfs

               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 Device 11>/
… <EPF Device 21>/
.. /
… <EPF Device 12>/
… <EPF Device 22>/

In order to create a of the type probed by , the
user has to create a directory inside .

Every 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 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/
.. /
… /
… /
… start
.. /
… /
… /
… start

The directory will have a list of symbolic links to
. These symbolic links should be created by the user to
represent the functions present in the endpoint device.

The 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