src/core/console.c

   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  */
  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  */
  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  */
  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  */
 128 int iskey ( void ) {
 129         return has_input() ? 1 : 0;
 130 }