Documentation/input/userio.rst

Source file repositories/reference/linux-study-clean/Documentation/input/userio.rst

File Facts

System
Linux kernel
Corpus path
Documentation/input/userio.rst
Extension
.rst
Size
2920 bytes
Lines
86
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

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

Annotation

Implementation Notes