.. SPDX-License-Identifier: GPL-2.0 ======================================= Configuring PCI Endpoint Using CONFIGFS ======================================= :Author: Kishon Vijay Abraham I 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 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/ .. / ... / ... / ... / .. / ... / ... / 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) :: .. / ... / ... vendorid ... deviceid ... revid ... progif_code ... subclass_code ... baseclass_code ... cache_line_size ... subsys_vendor_id ... subsys_id ... interrupt_pin ... / ... primary/ ... / ... secondary/ ... / If an EPF device has to be associated with 2 EPCs (like in the case of Non-transparent bridge), symlink of endpoint controller connected to primary interface should be added in 'primary' directory and symlink of endpoint controller connected to secondary interface should be added in 'secondary' directory. The directory can have a list of symbolic links () to other . These symbolic links should be created by the user to represent the virtual functions that are bound to the physical function. In the above directory structure is a physical function and is a virtual function. An EPF device once it's linked to another EPF device, cannot be linked to a EPC device. 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. Only that represents a physical function can be linked to a EPC 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/ | / | | start | functions/ | / | / | 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.rst