1.. SPDX-License-Identifier: GPL-2.0
2
3=======================================
4Configuring PCI Endpoint Using CONFIGFS
5=======================================
6
7:Author: Kishon Vijay Abraham I <kishon@ti.com>
8
9The PCI Endpoint Core exposes configfs entry (pci_ep) to configure the
10PCI endpoint function and to bind the endpoint function
11with the endpoint controller. (For introducing other mechanisms to
12configure the PCI Endpoint Function refer to [1]).
13
14Mounting configfs
15=================
16
17The PCI Endpoint Core layer creates pci_ep directory in the mounted configfs
18directory. configfs can be mounted using the following command::
19
20	mount -t configfs none /sys/kernel/config
21
22Directory Structure
23===================
24
25The pci_ep configfs has two directories at its root: controllers and
26functions. Every EPC device present in the system will have an entry in
27the *controllers* directory and every EPF driver present in the system
28will have an entry in the *functions* directory.
29::
30
31	/sys/kernel/config/pci_ep/
32		.. controllers/
33		.. functions/
34
35Creating EPF Device
36===================
37
38Every registered EPF driver will be listed in controllers directory. The
39entries corresponding to EPF driver will be created by the EPF core.
40::
41
42	/sys/kernel/config/pci_ep/functions/
43		.. <EPF Driver1>/
44			... <EPF Device 11>/
45			... <EPF Device 21>/
46			... <EPF Device 31>/
47		.. <EPF Driver2>/
48			... <EPF Device 12>/
49			... <EPF Device 22>/
50
51In order to create a <EPF device> of the type probed by <EPF Driver>, the
52user has to create a directory inside <EPF DriverN>.
53
54Every <EPF device> directory consists of the following entries that can be
55used to configure the standard configuration header of the endpoint function.
56(These entries are created by the framework when any new <EPF Device> is
57created)
58::
59
60		.. <EPF Driver1>/
61			... <EPF Device 11>/
62				... vendorid
63				... deviceid
64				... revid
65				... progif_code
66				... subclass_code
67				... baseclass_code
68				... cache_line_size
69				... subsys_vendor_id
70				... subsys_id
71				... interrupt_pin
72			        ... <Symlink EPF Device 31>/
73                                ... primary/
74			                ... <Symlink EPC Device1>/
75                                ... secondary/
76			                ... <Symlink EPC Device2>/
77
78If an EPF device has to be associated with 2 EPCs (like in the case of
79Non-transparent bridge), symlink of endpoint controller connected to primary
80interface should be added in 'primary' directory and symlink of endpoint
81controller connected to secondary interface should be added in 'secondary'
82directory.
83
84The <EPF Device> directory can have a list of symbolic links
85(<Symlink EPF Device 31>) to other <EPF Device>. These symbolic links should
86be created by the user to represent the virtual functions that are bound to
87the physical function. In the above directory structure <EPF Device 11> is a
88physical function and <EPF Device 31> is a virtual function. An EPF device once
89it's linked to another EPF device, cannot be linked to a EPC device.
90
91EPC Device
92==========
93
94Every registered EPC device will be listed in controllers directory. The
95entries corresponding to EPC device will be created by the EPC core.
96::
97
98	/sys/kernel/config/pci_ep/controllers/
99		.. <EPC Device1>/
100			... <Symlink EPF Device11>/
101			... <Symlink EPF Device12>/
102			... start
103		.. <EPC Device2>/
104			... <Symlink EPF Device21>/
105			... <Symlink EPF Device22>/
106			... start
107
108The <EPC Device> directory will have a list of symbolic links to
109<EPF Device>. These symbolic links should be created by the user to
110represent the functions present in the endpoint device. Only <EPF Device>
111that represents a physical function can be linked to a EPC device.
112
113The <EPC Device> directory will also have a *start* field. Once
114"1" is written to this field, the endpoint device will be ready to
115establish the link with the host. This is usually done after
116all the EPF devices are created and linked with the EPC device.
117::
118
119			 | controllers/
120				| <Directory: EPC name>/
121					| <Symbolic Link: Function>
122					| start
123			 | functions/
124				| <Directory: EPF driver>/
125					| <Directory: EPF device>/
126						| vendorid
127						| deviceid
128						| revid
129						| progif_code
130						| subclass_code
131						| baseclass_code
132						| cache_line_size
133						| subsys_vendor_id
134						| subsys_id
135						| interrupt_pin
136						| function
137
138[1] Documentation/PCI/endpoint/pci-endpoint.rst
139