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1.. include:: <isonum.txt>2 3===================4The userio Protocol5===================6 7 8:Copyright: |copy| 2015 Stephen Chandler Paul <thatslyude@gmail.com>9 10Sponsored by Red Hat11 12 13Introduction14=============15 16This module is intended to try to make the lives of input driver developers17easier by allowing them to test various serio devices (mainly the various18touchpads found on laptops) without having to have the physical device in front19of them. userio accomplishes this by allowing any privileged userspace program20to directly interact with the kernel's serio driver and control a virtual serio21port from there.22 23Usage overview24==============25 26In order to interact with the userio kernel module, one simply opens the27/dev/userio character device in their applications. Commands are sent to the28kernel module by writing to the device, and any data received from the serio29driver is read as-is from the /dev/userio device. All of the structures and30macros you need to interact with the device are defined in <linux/userio.h> and31<linux/serio.h>.32 33Command Structure34=================35 36The 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 one44of the USERIO_CMD macros defined in <linux/userio.h>. ``data`` is the argument45that goes along with the command. In the event that the command doesn't have an46argument, this field can be left untouched and will be ignored by the kernel.47Each command should be sent by writing the struct directly to the character48device. In the event that the command you send is invalid, an error will be49returned by the character device and a more descriptive error will be printed50to the kernel log. Only one command can be sent at a time, any additional data51written to the character device after the initial command will be ignored.52 53To close the virtual serio port, just close /dev/userio.54 55Commands56========57 58USERIO_CMD_REGISTER59~~~~~~~~~~~~~~~~~~~60 61Registers the port with the serio driver and begins transmitting data back and62forth. Registration can only be performed once a port type is set with63USERIO_CMD_SET_PORT_TYPE. Has no argument.64 65USERIO_CMD_SET_PORT_TYPE66~~~~~~~~~~~~~~~~~~~~~~~~67 68Sets the type of port we're emulating, where ``data`` is the port type being69set. Can be any of the macros from <linux/serio.h>. For example: SERIO_804270would set the port type to be a normal PS/2 port.71 72USERIO_CMD_SEND_INTERRUPT73~~~~~~~~~~~~~~~~~~~~~~~~~74 75Sends an interrupt through the virtual serio port to the serio driver, where76``data`` is the interrupt data being sent.77 78Userspace tools79===============80 81The userio userspace tools are able to record PS/2 devices using some of the82debugging information from i8042, and play back the devices on /dev/userio. The83latest version of these tools can be found at:84 85 https://github.com/Lyude/ps2emu86