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diff --git a/Documentation/input/userio.txt b/Documentation/input/userio.txt new file mode 100644 index 000000000000..0880c0f447a6 --- /dev/null +++ b/Documentation/input/userio.txt @@ -0,0 +1,70 @@ + The userio Protocol + (c) 2015 Stephen Chandler Paul <thatslyude@gmail.com> + Sponsored by Red Hat +-------------------------------------------------------------------------------- + +1. 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. + +2. 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>. + +3. 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. + +4. Commands +~~~~~~~~~~~ + +4.1 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. + +4.2 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. + +4.3 USERIO_CMD_SEND_INTERRUPT +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + Sends an interrupt through the virtual serio port to the serio driver, where +"data" is the interrupt data being sent. + +5. 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 |