1 #include "stddef.h"
2 #include "console.h"
3 #include <gpxe/process.h>
4 #include <gpxe/nap.h>
5
6 /** @file */
7
8 FILE_LICENCE ( GPL2_OR_LATER );
9
10 /**
11 * Write a single character to each console device.
12 *
13 * @v character Character to be written
14 * @ret None -
15 * @err None -
16 *
17 * The character is written out to all enabled console devices, using
18 * each device's console_driver::putchar() method.
19 *
20 */
putchar(int character)21 void putchar ( int character ) {
22 struct console_driver *console;
23
24 /* Automatic LF -> CR,LF translation */
25 if ( character == '\n' )
26 putchar ( '\r' );
27
28 for_each_table_entry ( console, CONSOLES ) {
29 if ( ( ! console->disabled ) && console->putchar )
30 console->putchar ( character );
31 }
32 }
33
34 /**
35 * Check to see if any input is available on any console.
36 *
37 * @v None -
38 * @ret console Console device that has input available, if any.
39 * @ret NULL No console device has input available.
40 * @err None -
41 *
42 * All enabled console devices are checked once for available input
43 * using each device's console_driver::iskey() method. The first
44 * console device that has available input will be returned, if any.
45 *
46 */
has_input(void)47 static struct console_driver * has_input ( void ) {
48 struct console_driver *console;
49
50 for_each_table_entry ( console, CONSOLES ) {
51 if ( ( ! console->disabled ) && console->iskey ) {
52 if ( console->iskey () )
53 return console;
54 }
55 }
56 return NULL;
57 }
58
59 /**
60 * Read a single character from any console.
61 *
62 * @v None -
63 * @ret character Character read from a console.
64 * @err None -
65 *
66 * A character will be read from the first enabled console device that
67 * has input available using that console's console_driver::getchar()
68 * method. If no console has input available to be read, this method
69 * will block. To perform a non-blocking read, use something like
70 *
71 * @code
72 *
73 * int key = iskey() ? getchar() : -1;
74 *
75 * @endcode
76 *
77 * The character read will not be echoed back to any console.
78 *
79 */
getchar(void)80 int getchar ( void ) {
81 struct console_driver *console;
82 int character;
83
84 while ( 1 ) {
85 console = has_input();
86 if ( console && console->getchar ) {
87 character = console->getchar ();
88 break;
89 }
90
91 /* Doze for a while (until the next interrupt). This works
92 * fine, because the keyboard is interrupt-driven, and the
93 * timer interrupt (approx. every 50msec) takes care of the
94 * serial port, which is read by polling. This reduces the
95 * power dissipation of a modern CPU considerably, and also
96 * makes Etherboot waiting for user interaction waste a lot
97 * less CPU time in a VMware session.
98 */
99 cpu_nap();
100
101 /* Keep processing background tasks while we wait for
102 * input.
103 */
104 step();
105 }
106
107 /* CR -> LF translation */
108 if ( character == '\r' )
109 character = '\n';
110
111 return character;
112 }
113
114 /** Check for available input on any console.
115 *
116 * @v None -
117 * @ret True Input is available on a console
118 * @ret False Input is not available on any console
119 * @err None -
120 *
121 * All enabled console devices are checked once for available input
122 * using each device's console_driver::iskey() method. If any console
123 * device has input available, this call will return True. If this
124 * call returns True, you can then safely call getchar() without
125 * blocking.
126 *
127 */
iskey(void)128 int iskey ( void ) {
129 return has_input() ? 1 : 0;
130 }
131