linux - Documentation/input/userio.rst

104 lines · 3.4 KiB

1	.. include:: <isonum.txt>
2
3	===================
4	The userio Protocol
5	===================
6
7
8	:Copyright: \|copy\| 2015 Lyude Paul <[email protected]>
9
10	Sponsored by Red Hat
11
12
13	Introduction
14	=============
15
16	This module is intended to try to make the lives of input driver developers
17	easier by allowing them to test various serio devices (mainly the various
18	touchpads found on laptops) without having to have the physical device in front
19	of them. userio accomplishes this by allowing any privileged userspace program
20	to directly interact with the kernel's serio driver and control a virtual serio
21	port from there.
22
23	Usage overview
24	==============
25
26	In order to interact with the userio kernel module, one simply opens the
27	/dev/userio character device in their applications. Commands are sent to the
28	kernel module by writing to the device, and any data received from the serio
29	driver is read as-is from the /dev/userio device. All of the structures and
30	macros you need to interact with the device are defined in <linux/userio.h> and
31	<linux/serio.h>.
32
33	Command Structure
34	=================
35
36	The struct used for sending commands to /dev/userio is as follows::
37
38	struct userio_cmd {
39	__u8 type;
40	__u8 data;
41	};
42
43	``type`` describes the type of command that is being sent. This can be any one
44	of the USERIO_CMD macros defined in <linux/userio.h>. ``data`` is the argument
45	that goes along with the command. In the event that the command doesn't have an
46	argument, this field can be left untouched and will be ignored by the kernel.
47	Each command should be sent by writing the struct directly to the character
48	device. In the event that the command you send is invalid, an error will be
49	returned by the character device and a more descriptive error will be printed
50	to the kernel log. Only one command can be sent at a time, any additional data
51	written to the character device after the initial command will be ignored.
52
53	To close the virtual serio port, just close /dev/userio.
54
55	Commands
56	========
57
58	USERIO_CMD_REGISTER
59	~~~~~~~~~~~~~~~~~~~
60
61	Registers the port with the serio driver and begins transmitting data back and
62	forth. Registration can only be performed once a port type is set with
63	USERIO_CMD_SET_PORT_TYPE. Has no argument.
64
65	USERIO_CMD_SET_PORT_TYPE
66	~~~~~~~~~~~~~~~~~~~~~~~~
67
68	Sets the type of port we're emulating, where ``data`` is the port type being
69	set. Can be any of the serio type macros from <linux/serio.h>. For example:
70	SERIO_8042 would set the port type to be a normal PS/2 port.
71
72	USERIO_CMD_SET_PORT_PROTO
73	~~~~~~~~~~~~~~~~~~~~~~~~~
74
75	Sets the protocol of port we're emulating, where ``data`` is the protocol being
76	set. Can be any of the serio proto macros from <linux/serio.h>. For example:
77	SERIO_IFORCE would set the port type to be an I-Force serial joystick.
78
79	USERIO_CMD_SET_PORT_ID
80	~~~~~~~~~~~~~~~~~~~~~~
81
82	Sets the ``id`` value on the identification of port we're emulating, where
83	``data`` is the value being set.
84
85	USERIO_CMD_SET_PORT_EXTRA
86	~~~~~~~~~~~~~~~~~~~~~~~~~
87
88	Sets the ``extra`` value on the identification of port we're emulating, where
89	``data`` is the value being set.
90
91	USERIO_CMD_SEND_INTERRUPT
92	~~~~~~~~~~~~~~~~~~~~~~~~~
93
94	Sends an interrupt through the virtual serio port to the serio driver, where
95	``data`` is the interrupt data being sent.
96
97	Userspace tools
98	===============
99
100	The userio userspace tools are able to record PS/2 devices using some of the
101	debugging information from i8042, and play back the devices on /dev/userio. The
102	latest version of these tools can be found at:
103
104	https://github.com/Lyude/ps2emu