71 lines
2.9 KiB
Text
71 lines
2.9 KiB
Text
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The userio Protocol
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(c) 2015 Stephen Chandler Paul <thatslyude@gmail.com>
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Sponsored by Red Hat
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--------------------------------------------------------------------------------
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1. Introduction
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~~~~~~~~~~~~~~~
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This module is intended to try to make the lives of input driver developers
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easier by allowing them to test various serio devices (mainly the various
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touchpads found on laptops) without having to have the physical device in front
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of them. userio accomplishes this by allowing any privileged userspace program
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to directly interact with the kernel's serio driver and control a virtual serio
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port from there.
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2. Usage overview
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~~~~~~~~~~~~~~~~~
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In order to interact with the userio kernel module, one simply opens the
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/dev/userio character device in their applications. Commands are sent to the
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kernel module by writing to the device, and any data received from the serio
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driver is read as-is from the /dev/userio device. All of the structures and
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macros you need to interact with the device are defined in <linux/userio.h> and
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<linux/serio.h>.
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3. Command Structure
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~~~~~~~~~~~~~~~~~~~~
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The struct used for sending commands to /dev/userio is as follows:
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struct userio_cmd {
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__u8 type;
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__u8 data;
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};
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"type" describes the type of command that is being sent. This can be any one
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of the USERIO_CMD macros defined in <linux/userio.h>. "data" is the argument
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that goes along with the command. In the event that the command doesn't have an
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argument, this field can be left untouched and will be ignored by the kernel.
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Each command should be sent by writing the struct directly to the character
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device. In the event that the command you send is invalid, an error will be
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returned by the character device and a more descriptive error will be printed
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to the kernel log. Only one command can be sent at a time, any additional data
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written to the character device after the initial command will be ignored.
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To close the virtual serio port, just close /dev/userio.
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4. Commands
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~~~~~~~~~~~
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4.1 USERIO_CMD_REGISTER
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~~~~~~~~~~~~~~~~~~~~~~~
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Registers the port with the serio driver and begins transmitting data back and
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forth. Registration can only be performed once a port type is set with
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USERIO_CMD_SET_PORT_TYPE. Has no argument.
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4.2 USERIO_CMD_SET_PORT_TYPE
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Sets the type of port we're emulating, where "data" is the port type being
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set. Can be any of the macros from <linux/serio.h>. For example: SERIO_8042
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would set the port type to be a normal PS/2 port.
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4.3 USERIO_CMD_SEND_INTERRUPT
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Sends an interrupt through the virtual serio port to the serio driver, where
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"data" is the interrupt data being sent.
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5. Userspace tools
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~~~~~~~~~~~~~~~~~~
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The userio userspace tools are able to record PS/2 devices using some of the
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debugging information from i8042, and play back the devices on /dev/userio. The
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latest version of these tools can be found at:
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https://github.com/Lyude/ps2emu
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