treewide: remove redundant IS_ERR() before error code check

[linux/fpc-iii.git] / Documentation / input / devices / atarikbd.rst

====================================
Intelligent Keyboard (ikbd) Protocol
====================================


Introduction
============

The Atari Corp. Intelligent Keyboard (ikbd) is a general purpose keyboard
controller that is flexible enough that it can be used in a variety of
products without modification. The keyboard, with its microcontroller,
provides a convenient connection point for a mouse and switch-type joysticks.
The ikbd processor also maintains a time-of-day clock with one second
resolution.
The ikbd has been designed to be general enough that it can be used with a
variety of new computer products. Product variations in a number of
keyswitches, mouse resolution, etc. can be accommodated.
The ikbd communicates with the main processor over a high speed bi-directional
serial interface. It can function in a variety of modes to facilitate
different applications of the keyboard,  joysticks, or mouse. Limited use of
the controller is possible in applications in which only a unidirectional
communications medium is available by carefully designing the default modes.

Keyboard
========

The keyboard always returns key make/break scan codes. The ikbd generates
keyboard scan codes for each key press and release. The key scan make (key
closure) codes start at 1, and are defined in Appendix A. For example, the
ISO key position in the scan code table should exist even if no keyswitch
exists in that position on a particular keyboard. The break code for each key
is obtained by ORing 0x80 with the make code.

The special codes 0xF6 through 0xFF are reserved for use as follows:

=================== ====================================================
    Code            Command
=================== ====================================================
    0xF6            status report
    0xF7            absolute mouse position record
    0xF8-0xFB       relative mouse position records (lsbs determined by
                    mouse button states)
    0xFC            time-of-day
    0xFD            joystick report (both sticks)
    0xFE            joystick 0 event
    0xFF            joystick 1 event
=================== ====================================================

The two shift keys return different scan codes in this mode. The ENTER key
and the RETurn key are also distinct.

Mouse
=====

The mouse port should be capable of supporting a mouse with resolution of
approximately 200 counts (phase changes or 'clicks') per inch of travel. The
mouse should be scanned at a rate that will permit accurate tracking at
velocities up to 10 inches per second.
The ikbd can report mouse motion in three distinctly different ways. It can
report relative motion, absolute motion in a coordinate system maintained
within the ikbd, or by converting mouse motion into keyboard cursor control
key equivalents.
The mouse buttons can be treated as part of the mouse or as additional
keyboard keys.

Relative Position Reporting
---------------------------

In relative position mode, the ikbd will return relative mouse position
records whenever a mouse event occurs. A mouse event consists of a mouse
button being pressed or released, or motion in either axis exceeding a
settable threshold of motion. Regardless of the threshold, all bits of
resolution are returned to the host computer.
Note that the ikbd may return mouse relative position reports with
significantly more than the threshold delta x or y. This may happen since no
relative mouse motion events will be generated: (a) while the keyboard has
been 'paused' ( the event will be stored until keyboard communications is
resumed) (b) while any event is being transmitted.

The relative mouse position record is a three byte record of the form
(regardless of keyboard mode)::

    %111110xy           ; mouse position record flag
                        ; where y is the right button state
                        ; and x is the left button state
    X                   ; delta x as twos complement integer
    Y                   ; delta y as twos complement integer

Note that the value of the button state bits should be valid even if the
MOUSE BUTTON ACTION has set the buttons to act like part of the keyboard.
If the accumulated motion before the report packet is generated exceeds the
+127...-128 range, the motion is broken into multiple packets.
Note that the sign of the delta y reported is a function of the Y origin
selected.

Absolute Position reporting
---------------------------

The ikbd can also maintain absolute mouse position. Commands exist for
resetting the mouse position, setting X/Y scaling, and interrogating the
current mouse position.

Mouse Cursor Key Mode
---------------------

The ikbd can translate mouse motion into the equivalent cursor keystrokes.
The number of mouse clicks per keystroke is independently programmable in
each axis. The ikbd internally maintains mouse motion information to the
highest resolution available, and merely generates a pair of cursor key events
for each multiple of the scale factor.
Mouse motion produces the cursor key make code immediately followed by the
break code for the appropriate cursor key. The mouse buttons produce scan
codes above those normally assigned for the largest envisioned keyboard (i.e.
LEFT=0x74 & RIGHT=0x75).

Joystick
========

Joystick Event Reporting
------------------------

In this mode, the ikbd generates a record whenever the joystick position is
changed (i.e. for each opening or closing of a joystick switch or trigger).

The joystick event record is two bytes of the form::

    %1111111x           ; Joystick event marker
                        ; where x is Joystick 0 or 1
    %x000yyyy           ; where yyyy is the stick position
                        ; and x is the trigger

Joystick Interrogation
----------------------

The current state of the joystick ports may be interrogated at any time in
this mode by sending an 'Interrogate Joystick' command to the ikbd.

The ikbd response to joystick interrogation is a three byte report of the form::

    0xFD                ; joystick report header
    %x000yyyy           ; Joystick 0
    %x000yyyy           ; Joystick 1
                        ; where x is the trigger
                        ; and yyy is the stick position

Joystick Monitoring
-------------------

A mode is available that devotes nearly all of the keyboard communications
time to reporting the state of the joystick ports at a user specifiable rate.
It remains in this mode until reset or commanded into another mode. The PAUSE
command in this mode not only stop the output but also temporarily stops
scanning the joysticks (samples are not queued).

Fire Button Monitoring
----------------------

A mode is provided to permit monitoring a single input bit at a high rate. In
this mode the ikbd monitors the state of the Joystick 1 fire button at the
maximum rate permitted by the serial communication channel. The data is packed
8 bits per byte for transmission to the host. The ikbd remains in this mode
until reset or commanded into another mode. The PAUSE command in this mode not
only stops the output but also temporarily stops scanning the button (samples
are not queued).

Joystick Key Code Mode
----------------------

The ikbd may be commanded to translate the use of either joystick into the
equivalent cursor control keystroke(s). The ikbd provides a single breakpoint
velocity joystick cursor.
Joystick events produce the make code, immediately followed by the break code
for the appropriate cursor motion keys. The trigger or fire buttons of the
joysticks produce pseudo key scan codes above those used by the largest key
matrix envisioned (i.e. JOYSTICK0=0x74, JOYSTICK1=0x75).

Time-of-Day Clock
=================

The ikbd also maintains a time-of-day clock for the system. Commands are
available to set and interrogate the timer-of-day clock. Time-keeping is
maintained down to a resolution of one second.

Status Inquiries
================

The current state of ikbd modes and parameters may be found by sending status
inquiry commands that correspond to the ikbd set commands.

Power-Up Mode
=============

The keyboard controller will perform a simple self-test on power-up to detect
major controller faults (ROM checksum and RAM test) and such things as stuck
keys. Any keys down at power-up are presumed to be stuck, and their BREAK
(sic) code is returned (which without the preceding MAKE code is a flag for a
keyboard error). If the controller self-test completes without error, the code
0xF0 is returned. (This code will be used to indicate the version/release of
the ikbd controller. The first release of the ikbd is version 0xF0, should
there be a second release it will be 0xF1, and so on.)
The ikbd defaults to a mouse position reporting with threshold of 1 unit in
either axis and the Y=0 origin at the top of the screen, and joystick event
reporting mode for joystick 1, with both buttons being logically assigned to
the mouse. After any joystick command, the ikbd assumes that joysticks are
connected to both Joystick0 and Joystick1. Any mouse command (except MOUSE
DISABLE) then causes port 0 to again be scanned as if it were a mouse, and
both buttons are logically connected to it. If a mouse disable command is
received while port 0 is presumed to be a mouse, the button is logically
assigned to Joystick1 (until the mouse is reenabled by another mouse command).

ikbd Command Set
================

This section contains a list of commands that can be sent to the ikbd. Command
codes (such as 0x00) which are not specified should perform no operation
(NOPs).

RESET
-----

::

    0x80
    0x01

N.B. The RESET command is the only two byte command understood by the ikbd.
Any byte following an 0x80 command byte other than 0x01 is ignored (and causes
the 0x80 to be ignored).
A reset may also be caused by sending a break lasting at least 200mS to the
ikbd.
Executing the RESET command returns the keyboard to its default (power-up)
mode and parameter settings. It does not affect the time-of-day clock.
The RESET command or function causes the ikbd to perform a simple self-test.
If the test is successful, the ikbd will send the code of 0xF0 within 300mS
of receipt of the RESET command (or the end of the break, or power-up). The
ikbd will then scan the key matrix for any stuck (closed) keys. Any keys found
closed will cause the break scan code to be generated (the break code arriving
without being preceded by the make code is a flag for a key matrix error).

SET MOUSE BUTTON ACTION
-----------------------

::

    0x07
    %00000mss           ; mouse button action
                        ;       (m is presumed = 1 when in MOUSE KEYCODE mode)
                        ; mss=0xy, mouse button press or release causes mouse
                        ;  position report
                        ;  where y=1, mouse key press causes absolute report
                        ;  and x=1, mouse key release causes absolute report
                        ; mss=100, mouse buttons act like keys

This command sets how the ikbd should treat the buttons on the mouse. The
default mouse button action mode is %00000000, the buttons are treated as part
of the mouse logically.
When buttons act like keys, LEFT=0x74 & RIGHT=0x75.

SET RELATIVE MOUSE POSITION REPORTING
-------------------------------------

::

    0x08

Set relative mouse position reporting. (DEFAULT) Mouse position packets are
generated asynchronously by the ikbd whenever motion exceeds the setable
threshold in either axis (see SET MOUSE THRESHOLD). Depending upon the mouse
key mode, mouse position reports may also be generated when either mouse
button is pressed or released. Otherwise the mouse buttons behave as if they
were keyboard keys.

SET ABSOLUTE MOUSE POSITIONING
------------------------------

::

    0x09
    XMSB                ; X maximum (in scaled mouse clicks)
    XLSB
    YMSB                ; Y maximum (in scaled mouse clicks)
    YLSB

Set absolute mouse position maintenance. Resets the ikbd maintained X and Y
coordinates.
In this mode, the value of the internally maintained coordinates does NOT wrap
between 0 and large positive numbers. Excess motion below 0 is ignored. The
command sets the maximum positive value that can be attained in the scaled
coordinate system. Motion beyond that value is also ignored.

SET MOUSE KEYCODE MOSE
----------------------

::

    0x0A
    deltax              ; distance in X clicks to return (LEFT) or (RIGHT)
    deltay              ; distance in Y clicks to return (UP) or (DOWN)

Set mouse monitoring routines to return cursor motion keycodes instead of
either RELATIVE or ABSOLUTE motion records. The ikbd returns the appropriate
cursor keycode after mouse travel exceeding the user specified deltas in
either axis. When the keyboard is in key scan code mode, mouse motion will
cause the make code immediately followed by the break code. Note that this
command is not affected by the mouse motion origin.

SET MOUSE THRESHOLD
-------------------

::

    0x0B
    X                   ; x threshold in mouse ticks (positive integers)
    Y                   ; y threshold in mouse ticks (positive integers)

This command sets the threshold before a mouse event is generated. Note that
it does NOT affect the resolution of the data returned to the host. This
command is valid only in RELATIVE MOUSE POSITIONING mode. The thresholds
default to 1 at RESET (or power-up).

SET MOUSE SCALE
---------------

::

    0x0C
    X                   ; horizontal mouse ticks per internal X
    Y                   ; vertical mouse ticks per internal Y

This command sets the scale factor for the ABSOLUTE MOUSE POSITIONING mode.
In this mode, the specified number of mouse phase changes ('clicks') must
occur before the internally maintained coordinate is changed by one
(independently scaled for each axis). Remember that the mouse position
information is available only by interrogating the ikbd in the ABSOLUTE MOUSE
POSITIONING mode unless the ikbd has been commanded to report on button press
or release (see SET MOSE BUTTON ACTION).

INTERROGATE MOUSE POSITION
--------------------------

::

    0x0D
    Returns:
            0xF7       ; absolute mouse position header
    BUTTONS
            0000dcba   ; where a is right button down since last interrogation
                       ; b is right button up since last
                       ; c is left button down since last
                       ; d is left button up since last
            XMSB       ; X coordinate
            XLSB
            YMSB       ; Y coordinate
            YLSB

The INTERROGATE MOUSE POSITION command is valid when in the ABSOLUTE MOUSE
POSITIONING mode, regardless of the setting of the MOUSE BUTTON ACTION.

LOAD MOUSE POSITION
-------------------

::

    0x0E
    0x00                ; filler
    XMSB                ; X coordinate
    XLSB                ; (in scaled coordinate system)
    YMSB                ; Y coordinate
    YLSB

This command allows the user to preset the internally maintained absolute
mouse position.

SET Y=0 AT BOTTOM
-----------------

::

    0x0F

This command makes the origin of the Y axis to be at the bottom of the
logical coordinate system internal to the ikbd for all relative or absolute
mouse motion. This causes mouse motion toward the user to be negative in sign
and away from the user to be positive.

SET Y=0 AT TOP
--------------

::

    0x10

Makes the origin of the Y axis to be at the top of the logical coordinate
system within the ikbd for all relative or absolute mouse motion. (DEFAULT)
This causes mouse motion toward the user to be positive in sign and away from
the user to be negative.

RESUME
------

::

    0x11

Resume sending data to the host. Since any command received by the ikbd after
its output has been paused also causes an implicit RESUME this command can be
thought of as a NO OPERATION command. If this command is received by the ikbd
and it is not PAUSED, it is simply ignored.

DISABLE MOUSE
-------------

::

    0x12

All mouse event reporting is disabled (and scanning may be internally
disabled). Any valid mouse mode command resumes mouse motion monitoring. (The
valid mouse mode commands are SET RELATIVE MOUSE POSITION REPORTING, SET
ABSOLUTE MOUSE POSITIONING, and SET MOUSE KEYCODE MODE. )
N.B. If the mouse buttons have been commanded to act like keyboard keys, this
command DOES affect their actions.

PAUSE OUTPUT
------------

::

    0x13

Stop sending data to the host until another valid command is received. Key
matrix activity is still monitored and scan codes or ASCII characters enqueued
(up to the maximum supported by the microcontroller) to be sent when the host
allows the output to be resumed. If in the JOYSTICK EVENT REPORTING mode,
joystick events are also queued.
Mouse motion should be accumulated while the output is paused. If the ikbd is
in RELATIVE MOUSE POSITIONING REPORTING mode, motion is accumulated beyond the
normal threshold limits to produce the minimum number of packets necessary for
transmission when output is resumed. Pressing or releasing either mouse button
causes any accumulated motion to be immediately queued as packets, if the
mouse is in RELATIVE MOUSE POSITION REPORTING mode.
Because of the limitations of the microcontroller memory this command should
be used sparingly, and the output should not be shut of for more than <tbd>
milliseconds at a time.
The output is stopped only at the end of the current 'even'. If the PAUSE
OUTPUT command is received in the middle of a multiple byte report, the packet
will still be transmitted to conclusion and then the PAUSE will take effect.
When the ikbd is in either the JOYSTICK MONITORING mode or the FIRE BUTTON
MONITORING mode, the PAUSE OUTPUT command also temporarily stops the
monitoring process (i.e. the samples are not enqueued for transmission).

SET JOYSTICK EVENT REPORTING
----------------------------

::

    0x14

Enter JOYSTICK EVENT REPORTING mode (DEFAULT). Each opening or closure of a
joystick switch or trigger causes a joystick event record to be generated.

SET JOYSTICK INTERROGATION MODE
-------------------------------

::

    0x15

Disables JOYSTICK EVENT REPORTING. Host must send individual JOYSTICK
INTERROGATE commands to sense joystick state.

JOYSTICK INTERROGATE
--------------------

::

    0x16

Return a record indicating the current state of the joysticks. This command
is valid in either the JOYSTICK EVENT REPORTING mode or the JOYSTICK
INTERROGATION MODE.

SET JOYSTICK MONITORING
-----------------------

::

    0x17
    rate                ; time between samples in hundredths of a second
    Returns: (in packets of two as long as in mode)
            %000000xy   ; where y is JOYSTICK1 Fire button
                        ; and x is JOYSTICK0 Fire button
            %nnnnmmmm   ; where m is JOYSTICK1 state
                        ; and n is JOYSTICK0 state

Sets the ikbd to do nothing but monitor the serial command line, maintain the
time-of-day clock, and monitor the joystick. The rate sets the interval
between joystick samples.
N.B. The user should not set the rate higher than the serial communications
channel will allow the 2 bytes packets to be transmitted.

SET FIRE BUTTON MONITORING
--------------------------

::

    0x18
    Returns: (as long as in mode)
            %bbbbbbbb   ; state of the JOYSTICK1 fire button packed
                        ; 8 bits per byte, the first sample if the MSB

Set the ikbd to do nothing but monitor the serial command line, maintain the
time-of-day clock, and monitor the fire button on Joystick 1. The fire button
is scanned at a rate that causes 8 samples to be made in the time it takes for
the previous byte to be sent to the host (i.e. scan rate = 8/10 * baud rate).
The sample interval should be as constant as possible.

SET JOYSTICK KEYCODE MODE
-------------------------

::

    0x19
    RX                  ; length of time (in tenths of seconds) until
                        ; horizontal velocity breakpoint is reached
    RY                  ; length of time (in tenths of seconds) until
                        ; vertical velocity breakpoint is reached
    TX                  ; length (in tenths of seconds) of joystick closure
                        ; until horizontal cursor key is generated before RX
                        ; has elapsed
    TY                  ; length (in tenths of seconds) of joystick closure
                        ; until vertical cursor key is generated before RY
                        ; has elapsed
    VX                  ; length (in tenths of seconds) of joystick closure
                        ; until horizontal cursor keystrokes are generated
                        ; after RX has elapsed
    VY                  ; length (in tenths of seconds) of joystick closure
                        ; until vertical cursor keystrokes are generated
                        ; after RY has elapsed

In this mode, joystick 0 is scanned in a way that simulates cursor keystrokes.
On initial closure, a keystroke pair (make/break) is generated. Then up to Rn
tenths of seconds later, keystroke pairs are generated every Tn tenths of
seconds. After the Rn breakpoint is reached, keystroke pairs are generated
every Vn tenths of seconds. This provides a velocity (auto-repeat) breakpoint
feature.
Note that by setting RX and/or Ry to zero, the velocity feature can be
disabled. The values of TX and TY then become meaningless, and the generation
of cursor 'keystrokes' is set by VX and VY.

DISABLE JOYSTICKS
-----------------

::

    0x1A

Disable the generation of any joystick events (and scanning may be internally
disabled). Any valid joystick mode command resumes joystick monitoring. (The
joystick mode commands are SET JOYSTICK EVENT REPORTING, SET JOYSTICK
INTERROGATION MODE, SET JOYSTICK MONITORING, SET FIRE BUTTON MONITORING, and
SET JOYSTICK KEYCODE MODE.)

TIME-OF-DAY CLOCK SET
---------------------

::

    0x1B
    YY                  ; year (2 least significant digits)
    MM                  ; month
    DD                  ; day
    hh                  ; hour
    mm                  ; minute
    ss                  ; second

All time-of-day data should be sent to the ikbd in packed BCD format.
Any digit that is not a valid BCD digit should be treated as a 'don't care'
and not alter that particular field of the date or time. This permits setting
only some subfields of the time-of-day clock.

INTERROGATE TIME-OF-DAT CLOCK
-----------------------------

::

    0x1C
    Returns:
            0xFC        ; time-of-day event header
            YY          ; year (2 least significant digits)
            MM          ; month
            DD          ; day
            hh          ; hour
            mm          ; minute
            ss          ; second

    All time-of-day is sent in packed BCD format.

MEMORY LOAD
-----------

::

    0x20
    ADRMSB              ; address in controller
    ADRLSB              ; memory to be loaded
    NUM                 ; number of bytes (0-128)
    { data }

This command permits the host to load arbitrary values into the ikbd
controller memory. The time between data bytes must be less than 20ms.

MEMORY READ
-----------

::

    0x21
    ADRMSB              ; address in controller
    ADRLSB              ; memory to be read
    Returns:
            0xF6        ; status header
            0x20        ; memory access
            { data }    ; 6 data bytes starting at ADR

This command permits the host to read from the ikbd controller memory.

CONTROLLER EXECUTE
------------------

::

    0x22
    ADRMSB              ; address of subroutine in
    ADRLSB              ; controller memory to be called

This command allows the host to command the execution of a subroutine in the
ikbd controller memory.

STATUS INQUIRIES
----------------

::

    Status commands are formed by inclusively ORing 0x80 with the
    relevant SET command.

    Example:
    0x88 (or 0x89 or 0x8A)  ; request mouse mode
    Returns:
            0xF6        ; status response header
            mode        ; 0x08 is RELATIVE
                        ; 0x09 is ABSOLUTE
                        ; 0x0A is KEYCODE
            param1      ; 0 is RELATIVE
                        ; XMSB maximum if ABSOLUTE
                        ; DELTA X is KEYCODE
            param2      ; 0 is RELATIVE
                        ; YMSB maximum if ABSOLUTE
                        ; DELTA Y is KEYCODE
            param3      ; 0 if RELATIVE
                        ; or KEYCODE
                        ; YMSB is ABSOLUTE
            param4      ; 0 if RELATIVE
                        ; or KEYCODE
                        ; YLSB is ABSOLUTE
            0           ; pad
            0

The STATUS INQUIRY commands request the ikbd to return either the current mode
or the parameters associated with a given command. All status reports are
padded to form 8 byte long return packets. The responses to the status
requests are designed so that the host may store them away (after stripping
off the status report header byte) and later send them back as commands to
ikbd to restore its state. The 0 pad bytes will be treated as NOPs by the
ikbd.

    Valid STATUS INQUIRY commands are::

            0x87    mouse button action
            0x88    mouse mode
            0x89
            0x8A
            0x8B    mnouse threshold
            0x8C    mouse scale
            0x8F    mouse vertical coordinates
            0x90    ( returns       0x0F Y=0 at bottom
                            0x10 Y=0 at top )
            0x92    mouse enable/disable
                    ( returns       0x00 enabled)
                            0x12 disabled )
            0x94    joystick mode
            0x95
            0x96
            0x9A    joystick enable/disable
                    ( returns       0x00 enabled
                            0x1A disabled )

It is the (host) programmer's responsibility to have only one unanswered
inquiry in process at a time.
STATUS INQUIRY commands are not valid if the ikbd is in JOYSTICK MONITORING
mode or FIRE BUTTON MONITORING mode.


SCAN CODES
==========

The key scan codes returned by the ikbd are chosen to simplify the
implementation of GSX.

GSX Standard Keyboard Mapping

======= ============
Hex     Keytop
======= ============
01      Esc
02      1
03      2
04      3
05      4
06      5
07      6
08      7
09      8
0A      9
0B      0
0C      \-
0D      \=
0E      BS
0F      TAB
10      Q
11      W
12      E
13      R
14      T
15      Y
16      U
17      I
18      O
19      P
1A      [
1B      ]
1C      RET
1D      CTRL
1E      A
1F      S
20      D
21      F
22      G
23      H
24      J
25      K
26      L
27      ;
28      '
29      \`
2A      (LEFT) SHIFT
2B      \\
2C      Z
2D      X
2E      C
2F      V
30      B
31      N
32      M
33      ,
34      .
35      /
36      (RIGHT) SHIFT
37      { NOT USED }
38      ALT
39      SPACE BAR
3A      CAPS LOCK
3B      F1
3C      F2
3D      F3
3E      F4
3F      F5
40      F6
41      F7
42      F8
43      F9
44      F10
45      { NOT USED }
46      { NOT USED }
47      HOME
48      UP ARROW
49      { NOT USED }
4A      KEYPAD -
4B      LEFT ARROW
4C      { NOT USED }
4D      RIGHT ARROW
4E      KEYPAD +
4F      { NOT USED }
50      DOWN ARROW
51      { NOT USED }
52      INSERT
53      DEL
54      { NOT USED }
5F      { NOT USED }
60      ISO KEY
61      UNDO
62      HELP
63      KEYPAD (
64      KEYPAD /
65      KEYPAD *
66      KEYPAD *
67      KEYPAD 7
68      KEYPAD 8
69      KEYPAD 9
6A      KEYPAD 4
6B      KEYPAD 5
6C      KEYPAD 6
6D      KEYPAD 1
6E      KEYPAD 2
6F      KEYPAD 3
70      KEYPAD 0
71      KEYPAD .
72      KEYPAD ENTER
======= ============