Based on kernel version 4.10.8. Page generated on 2017-04-01 14:43 EST.
1 The userio Protocol 2 (c) 2015 Stephen Chandler Paul <thatslyude@gmail.com> 3 Sponsored by Red Hat 4 -------------------------------------------------------------------------------- 5 6 1. Introduction 7 ~~~~~~~~~~~~~~~ 8 This module is intended to try to make the lives of input driver developers 9 easier by allowing them to test various serio devices (mainly the various 10 touchpads found on laptops) without having to have the physical device in front 11 of them. userio accomplishes this by allowing any privileged userspace program 12 to directly interact with the kernel's serio driver and control a virtual serio 13 port from there. 14 15 2. Usage overview 16 ~~~~~~~~~~~~~~~~~ 17 In order to interact with the userio kernel module, one simply opens the 18 /dev/userio character device in their applications. Commands are sent to the 19 kernel module by writing to the device, and any data received from the serio 20 driver is read as-is from the /dev/userio device. All of the structures and 21 macros you need to interact with the device are defined in <linux/userio.h> and 22 <linux/serio.h>. 23 24 3. Command Structure 25 ~~~~~~~~~~~~~~~~~~~~ 26 The struct used for sending commands to /dev/userio is as follows: 27 28 struct userio_cmd { 29 __u8 type; 30 __u8 data; 31 }; 32 33 "type" describes the type of command that is being sent. This can be any one 34 of the USERIO_CMD macros defined in <linux/userio.h>. "data" is the argument 35 that goes along with the command. In the event that the command doesn't have an 36 argument, this field can be left untouched and will be ignored by the kernel. 37 Each command should be sent by writing the struct directly to the character 38 device. In the event that the command you send is invalid, an error will be 39 returned by the character device and a more descriptive error will be printed 40 to the kernel log. Only one command can be sent at a time, any additional data 41 written to the character device after the initial command will be ignored. 42 To close the virtual serio port, just close /dev/userio. 43 44 4. Commands 45 ~~~~~~~~~~~ 46 47 4.1 USERIO_CMD_REGISTER 48 ~~~~~~~~~~~~~~~~~~~~~~~ 49 Registers the port with the serio driver and begins transmitting data back and 50 forth. Registration can only be performed once a port type is set with 51 USERIO_CMD_SET_PORT_TYPE. Has no argument. 52 53 4.2 USERIO_CMD_SET_PORT_TYPE 54 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 55 Sets the type of port we're emulating, where "data" is the port type being 56 set. Can be any of the macros from <linux/serio.h>. For example: SERIO_8042 57 would set the port type to be a normal PS/2 port. 58 59 4.3 USERIO_CMD_SEND_INTERRUPT 60 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 61 Sends an interrupt through the virtual serio port to the serio driver, where 62 "data" is the interrupt data being sent. 63 64 5. Userspace tools 65 ~~~~~~~~~~~~~~~~~~ 66 The userio userspace tools are able to record PS/2 devices using some of the 67 debugging information from i8042, and play back the devices on /dev/userio. The 68 latest version of these tools can be found at: 69 70 https://github.com/Lyude/ps2emu