1.. include:: <isonum.txt> 2 3=================== 4The userio Protocol 5=================== 6 7 8:Copyright: |copy| 2015 Stephen Chandler Paul <thatslyude@gmail.com> 9 10Sponsored by Red Hat 11 12 13Introduction 14============= 15 16This module is intended to try to make the lives of input driver developers 17easier by allowing them to test various serio devices (mainly the various 18touchpads found on laptops) without having to have the physical device in front 19of them. userio accomplishes this by allowing any privileged userspace program 20to directly interact with the kernel's serio driver and control a virtual serio 21port from there. 22 23Usage overview 24============== 25 26In 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 28kernel module by writing to the device, and any data received from the serio 29driver is read as-is from the /dev/userio device. All of the structures and 30macros you need to interact with the device are defined in <linux/userio.h> and 31<linux/serio.h>. 32 33Command Structure 34================= 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 one 44of the USERIO_CMD macros defined in <linux/userio.h>. ``data`` is the argument 45that goes along with the command. In the event that the command doesn't have an 46argument, 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 character 48device. In the event that the command you send is invalid, an error will be 49returned by the character device and a more descriptive error will be printed 50to the kernel log. Only one command can be sent at a time, any additional data 51written to the character device after the initial command will be ignored. 52 53To close the virtual serio port, just close /dev/userio. 54 55Commands 56======== 57 58USERIO_CMD_REGISTER 59~~~~~~~~~~~~~~~~~~~ 60 61Registers the port with the serio driver and begins transmitting data back and 62forth. Registration can only be performed once a port type is set with 63USERIO_CMD_SET_PORT_TYPE. Has no argument. 64 65USERIO_CMD_SET_PORT_TYPE 66~~~~~~~~~~~~~~~~~~~~~~~~ 67 68Sets the type of port we're emulating, where ``data`` is the port type being 69set. Can be any of the macros from <linux/serio.h>. For example: SERIO_8042 70would set the port type to be a normal PS/2 port. 71 72USERIO_CMD_SEND_INTERRUPT 73~~~~~~~~~~~~~~~~~~~~~~~~~ 74 75Sends an interrupt through the virtual serio port to the serio driver, where 76``data`` is the interrupt data being sent. 77 78Userspace tools 79=============== 80 81The userio userspace tools are able to record PS/2 devices using some of the 82debugging information from i8042, and play back the devices on /dev/userio. The 83latest version of these tools can be found at: 84 85 https://github.com/Lyude/ps2emu 86