keyboard.4 revision 423 
1.Dd April 7, 1993
2.Dt KEYBOARD 4
3.Os FreeBSD
4.Sh NAME
5.Nm keyboard
6.Nd pc keyboard interface
7.Sh DESCRIPTION
8
9The PC keyboard is use as the console character input device. The keyboard
10is owned by the current virtual console.
11To switch between the virtual consoles use the sequence 
12.Ar ALT+Fn
13, which means hold down ALT and press one of the function keys. The 
14virtual console with the same number as the function key is then
15selected as the current virtual console, and given exclusive use of
16the keyboard and display.
17
18The console allows entering values that are not physically
19present on the keyboard via a special keysequence.
20To use this facility press and hold down ALT,
21then enter a decimal number from 0-255 via the numerical keypad, then
22release ALT. The entered value is then used as the ASCII value for one
23character. This way it is possible to enter any ASCII value.
24The keyboard is configurable to suit the individual user and the different
25national layout.
26
27The keys on the keyboard can have any of the following functions:
28
29	Normal key	- Enter the ASCII value associated with the key.
30
31	Function key	- Enter a string of ASCII values.
32
33	Switch Key	- Switch virtual console.
34
35	Modifier Key	- Change the meaning of another key.
36
37
38The keyboard is seen as a number of keys numbered from 1 to n. This 
39number is often referred to as the "scancode" for a given key. The number
40of the key is transmitted as an 8 bit char with bit 7 as 0 when a key is 
41pressed, and the number with bit 7 as 1 when released. This makes it 
42possible to make the mapping of the keys fully configurable.
43
44The meaning of every key is programmable via the PIO_KEYMAP ioctl call, that
45takes a structure keymap_t as argument. The layout of this structure is as
46follows:
47.Pp
48.Bd -literal -offset indent
49		struct keymap {
50			u_short	n_keys;
51			struct key_t {
52				u_char map[NUM_STATES];
53				u_char spcl;
54				u_char flgs;
55			} key[NUM_KEYS];
56		};
57.Ed
58.Pp
59The field n_keys tells the system how many keydefinitions (scancodes)
60follows. Each scancode is then specified in the key_t substructure.
61
62Each scancode can be translated to any of 8 different values, depending
63on the shift, control, and alt state. These eight possibilities is 
64represented by the map array, as shown below:
65
66                                                            alt
67 scan                          cntrl          alt    alt   cntrl
68 code     base   shift  cntrl  shift   alt   shift  cntrl  shift
69 map[n]      0       1      2      3     4       5      6      7
70 ----     ------------------------------------------------------
71 0x1E      'a'     'A'   0x01   0x01    'a'    'A'   0x01   0x01
72
73This is the default mapping for the key labelled 'A' wich normally has 
74scancode 0x1E. The eight states is as shown, giving the 'A' key its 
75normal behavior. 
76The spcl field is used to give the key "special" treatment, and is
77interpreted as follows. 
78Each bit correspond to one of the states above. If the bit is 0 the 
79key emits the number defined in the corresponding map[] entry. 
80If the bit is 1 the key is "special". This means it does not emit 
81anything, instead it changes the "state". That means it is a shift, 
82control, alt, lock, switch-screen, function-key or no-op key. 
83The bitmap is backwards ie. 7 for base, 6 for shift etc.
84
85The flgs field defines if the key should react on caps-lock (1),
86num-lock (2), both (3) or ignore both (0). 
87
88The mapkbd utility is used to load such a description into/outof
89the kernel at runtime. This make it possible to change the key
90assignments at runtime, or more important to get (GIO_KEYMAP ioctl)
91the exact key meanings from the kernel (fx. used by the X server).
92
93The function keys can be programmed using the PIO_STRMAP ioctl call.
94
95This ioctl takes a argument of the type fkeyarg_t:
96.Bd -literal -offset indent
97		struct fkeyarg {
98			u_short	keynum;
99			char	keydef[MAXFK];
100			char	flen;
101		};
102.Ed
103.Pp
104The field keynum defines which function key that is programmed.
105The array keydef should contain the new string to be used (MAXFK long),
106and the length should be entered in flen.
107
108The GIO_STRMAP ioctl call works in a semilar manner, execpt it returns
109the current setting of keynum.
110
111The function keys are numbered like this:
112.Bd -literal -offset indent
113	F1-F12 			key 1 - 12
114	Shift F1-F12		key 13 - 24
115	Ctrl F1-F12		key 25 - 36
116	Ctrl+shift F1-F12	key 37 - 48
117	
118	Home			key 49
119	Up arrow		key 50
120	Page Up			key 51
121	(keypad) -		key 52
122	Left arrow		key 53
123	(keypad) 5		key 54
124	Right arrow		key 55
125	(keypad) +		key 56
126	End			key 57
127	Down arrow		key 58
128	Page down		key 59
129	Insert 			key 60
130.Ed
131.Pp
132.Sh AUTHOR
133 S_ren Schmidt 
134 Email: (baukno@login.dkuug.dk -or- sos@kmd-ac.dk)
135