[linux-2.6-block.git] / Documentation / input / userio.rst

.. include:: <isonum.txt>

===================
The userio Protocol
===================


:Copyright: |copy| 2015 Stephen Chandler Paul <thatslyude@gmail.com>

Sponsored by Red Hat


Introduction
=============

This module is intended to try to make the lives of input driver developers
easier by allowing them to test various serio devices (mainly the various
touchpads found on laptops) without having to have the physical device in front
of them. userio accomplishes this by allowing any privileged userspace program
to directly interact with the kernel's serio driver and control a virtual serio
port from there.

Usage overview
==============

In order to interact with the userio kernel module, one simply opens the
/dev/userio character device in their applications. Commands are sent to the
kernel module by writing to the device, and any data received from the serio
driver is read as-is from the /dev/userio device. All of the structures and
macros you need to interact with the device are defined in <linux/userio.h> and
<linux/serio.h>.

Command Structure
=================

The struct used for sending commands to /dev/userio is as follows::

	struct userio_cmd {
		__u8 type;
		__u8 data;
	};

``type`` describes the type of command that is being sent. This can be any one
of the USERIO_CMD macros defined in <linux/userio.h>. ``data`` is the argument
that goes along with the command. In the event that the command doesn't have an
argument, this field can be left untouched and will be ignored by the kernel.
Each command should be sent by writing the struct directly to the character
device. In the event that the command you send is invalid, an error will be
returned by the character device and a more descriptive error will be printed
to the kernel log. Only one command can be sent at a time, any additional data
written to the character device after the initial command will be ignored.

To close the virtual serio port, just close /dev/userio.

Commands
========

USERIO_CMD_REGISTER
~~~~~~~~~~~~~~~~~~~

Registers the port with the serio driver and begins transmitting data back and
forth. Registration can only be performed once a port type is set with
USERIO_CMD_SET_PORT_TYPE. Has no argument.

USERIO_CMD_SET_PORT_TYPE
~~~~~~~~~~~~~~~~~~~~~~~~

Sets the type of port we're emulating, where ``data`` is the port type being
set. Can be any of the macros from <linux/serio.h>. For example: SERIO_8042
would set the port type to be a normal PS/2 port.

USERIO_CMD_SEND_INTERRUPT
~~~~~~~~~~~~~~~~~~~~~~~~~

Sends an interrupt through the virtual serio port to the serio driver, where
``data`` is the interrupt data being sent.

Userspace tools
===============

The userio userspace tools are able to record PS/2 devices using some of the
debugging information from i8042, and play back the devices on /dev/userio. The
latest version of these tools can be found at:

	https://github.com/Lyude/ps2emu
Commit	Line	Data
730518f2 MCC	1	.. include:: <isonum.txt>
	2
	3	===================
	4	The userio Protocol
	5	===================
	6
	7
	8	:Copyright: \|copy\| 2015 Stephen Chandler Paul <thatslyude@gmail.com>
	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
5523662e SCP	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
730518f2 MCC	23	Usage overview
	24	==============
	25
	26	In order to interact with the userio kernel module, one simply opens the
5523662e SCP	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
730518f2 MCC	33	Command Structure
	34	=================
	35
	36	The struct used for sending commands to /dev/userio is as follows::
5523662e SCP	37
	38	struct userio_cmd {
	39	__u8 type;
	40	__u8 data;
	41	};
	42
730518f2 MCC	43	``type`` describes the type of command that is being sent. This can be any one
730518f2 MCC	44	of the USERIO_CMD macros defined in <linux/userio.h>. ``data`` is the argument
5523662e SCP	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.
5523662e	52
730518f2 MCC	53	To close the virtual serio port, just close /dev/userio.
	54
	55	Commands
	56	========
	57
	58	USERIO_CMD_REGISTER
	59	~~~~~~~~~~~~~~~~~~~
5523662e	60
730518f2	61	Registers the port with the serio driver and begins transmitting data back and
5523662e SCP	62	forth. Registration can only be performed once a port type is set with
	63	USERIO_CMD_SET_PORT_TYPE. Has no argument.
	64
730518f2 MCC	65	USERIO_CMD_SET_PORT_TYPE
	66	~~~~~~~~~~~~~~~~~~~~~~~~
	67
	68	Sets the type of port we're emulating, where ``data`` is the port type being
5523662e SCP	69	set. Can be any of the macros from <linux/serio.h>. For example: SERIO_8042
	70	would set the port type to be a normal PS/2 port.
	71
730518f2 MCC	72	USERIO_CMD_SEND_INTERRUPT
	73	~~~~~~~~~~~~~~~~~~~~~~~~~
	74
	75	Sends an interrupt through the virtual serio port to the serio driver, where
	76	``data`` is the interrupt data being sent.
	77
	78	Userspace tools
	79	===============
5523662e	80
730518f2	81	The userio userspace tools are able to record PS/2 devices using some of the
5523662e SCP	82	debugging information from i8042, and play back the devices on /dev/userio. The
	83	latest version of these tools can be found at:
	84
	85	https://github.com/Lyude/ps2emu