146 lines
4.9 KiB
Groff
146 lines
4.9 KiB
Groff
.Dd January 8, 1995
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.Dt KEYBOARD 4 i386
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.Os FreeBSD
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.Sh NAME
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.Nm keyboard
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.Nd pc keyboard interface
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.Sh DESCRIPTION
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The PC keyboard is used as the console character input device. The keyboard
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is owned by the current virtual console.
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To switch between the virtual consoles use the sequence
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.Ar ALT+Fn
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, which means hold down ALT and press one of the function keys. The
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virtual console with the same number as the function key is then
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selected as the current virtual console, and given exclusive use of
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the keyboard and display.
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The console allows entering values that are not physically
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present on the keyboard via a special keysequence.
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To use this facility press and hold down ALT,
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then enter a decimal number from 0-255 via the numerical keypad, then
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release ALT. The entered value is then used as the ASCII value for one
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character. This way it is possible to enter any ASCII value, not present
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on the keyboard.
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The console driver also includes a history function. It is activated by
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pressing the scroll-lock key. This holds the display, and enables the cursor
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arrows for scrolling up and down through the last scrolled out lines.
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The keyboard is configurable to suit the individual user and the different
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national layout.
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The keys on the keyboard can have any of the following functions:
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Normal key - Enter the ASCII value associated with the key.
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Function key - Enter a string of ASCII values.
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Switch Key - Switch virtual console.
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Modifier Key - Change the meaning of another key.
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The keyboard is seen as a number of keys numbered from 1 to n. This
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number is often referred to as the "scancode" for a given key. The number
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of the key is transmitted as an 8 bit char with bit 7 as 0 when a key is
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pressed, and the number with bit 7 as 1 when released. This makes it
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possible to make the mapping of the keys fully configurable.
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The meaning of every key is programmable via the PIO_KEYMAP ioctl call, that
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takes a structure keymap_t as argument. The layout of this structure is as
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follows:
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.Pp
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.Bd -literal -offset indent
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struct keymap {
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u_short n_keys;
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struct key_t {
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u_char map[NUM_STATES];
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u_char spcl;
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u_char flgs;
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} key[NUM_KEYS];
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};
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.Ed
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.Pp
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The field n_keys tells the system how many keydefinitions (scancodes)
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follows. Each scancode is then specified in the key_t substructure.
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Each scancode can be translated to any of 8 different values, depending
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on the shift, control, and alt state. These eight possibilities is
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represented by the map array, as shown below:
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alt
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scan cntrl alt alt cntrl
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code base shift cntrl shift alt shift cntrl shift
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map[n] 0 1 2 3 4 5 6 7
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---- ------------------------------------------------------
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0x1E 'a' 'A' 0x01 0x01 'a' 'A' 0x01 0x01
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This is the default mapping for the key labelled 'A' wich normally has
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scancode 0x1E. The eight states is as shown, giving the 'A' key its
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normal behavior.
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The spcl field is used to give the key "special" treatment, and is
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interpreted as follows.
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Each bit correspond to one of the states above. If the bit is 0 the
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key emits the number defined in the corresponding map[] entry.
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If the bit is 1 the key is "special". This means it does not emit
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anything, instead it changes the "state". That means it is a shift,
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control, alt, lock, switch-screen, function-key or no-op key.
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The bitmap is backwards ie. 7 for base, 6 for shift etc.
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The flgs field defines if the key should react on caps-lock (1),
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num-lock (2), both (3) or ignore both (0).
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The kbdcontrol utility is used to load such a description into/outof
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the kernel at runtime. This make it possible to change the key
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assignments at runtime, or more important to get (GIO_KEYMAP ioctl)
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the exact key meanings from the kernel (fx. used by the X server).
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The function keys can be programmed using the PIO_STRMAP ioctl call.
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This ioctl takes a argument of the type fkeyarg_t:
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.Bd -literal -offset indent
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struct fkeyarg {
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u_short keynum;
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char keydef[MAXFK];
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char flen;
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};
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.Ed
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.Pp
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The field keynum defines which function key that is programmed.
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The array keydef should contain the new string to be used (MAXFK long),
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and the length should be entered in flen.
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The GIO_STRMAP ioctl call works in a semilar manner, execpt it returns
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the current setting of keynum.
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The function keys are numbered like this:
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.Bd -literal -offset indent
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F1-F12 key 1 - 12
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Shift F1-F12 key 13 - 24
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Ctrl F1-F12 key 25 - 36
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Ctrl+shift F1-F12 key 37 - 48
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Home key 49
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Up arrow key 50
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Page Up key 51
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(keypad) - key 52
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Left arrow key 53
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(keypad) 5 key 54
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Right arrow key 55
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(keypad) + key 56
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End key 57
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Down arrow key 58
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Page down key 59
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Insert key 60
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Delete key 61
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Right window key 62
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Left window key 63
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Menu key 64
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.Ed
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The kbdcontrol utility also allows changing these values at runtime.
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.Pp
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.Sh AUTHOR
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S<>ren Schmidt (sos@FreeBSD.org)
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