drivers/staging/speakup/buffers.c

   1 #include <linux/console.h>
   2 #include <linux/types.h>
   3 #include <linux/wait.h>
   4
   5 #include "speakup.h"
   6 #include "spk_priv.h"
   7
   8 #define SYNTH_BUF_SIZE 8192     /* currently 8K bytes */
   9
  10 static u_char synth_buffer[SYNTH_BUF_SIZE];     /* guess what this is for! */
  11 static u_char *buff_in = synth_buffer;
  12 static u_char *buff_out = synth_buffer;
  13 static u_char *buffer_end = synth_buffer + SYNTH_BUF_SIZE - 1;
  14
  15 /* These try to throttle applications by stopping the TTYs
  16  * Note: we need to make sure that we will restart them eventually, which is
  17  * usually not possible to do from the notifiers. TODO: it should be possible
  18  * starting from linux 2.6.26.
  19  *
  20  * So we only stop when we know alive == 1 (else we discard the data anyway),
  21  * and the alive synth will eventually call start_ttys from the thread context.
  22  */
  23 void speakup_start_ttys(void)
  24 {
  25         int i;
  26
  27         for (i = 0; i < MAX_NR_CONSOLES; i++) {
  28                 if (speakup_console[i] && speakup_console[i]->tty_stopped)
  29                         continue;
  30                 if ((vc_cons[i].d != NULL) && (vc_cons[i].d->port.tty != NULL))
  31                         start_tty(vc_cons[i].d->port.tty);
  32         }
  33 }
  34 EXPORT_SYMBOL_GPL(speakup_start_ttys);
  35
  36 static void speakup_stop_ttys(void)
  37 {
  38         int i;
  39
  40         for (i = 0; i < MAX_NR_CONSOLES; i++)
  41                 if ((vc_cons[i].d != NULL) && (vc_cons[i].d->port.tty != NULL))
  42                         stop_tty(vc_cons[i].d->port.tty);
  43 }
  44
  45 static int synth_buffer_free(void)
  46 {
  47         int bytes_free;
  48
  49         if (buff_in >= buff_out)
  50                 bytes_free = SYNTH_BUF_SIZE - (buff_in - buff_out);
  51         else
  52                 bytes_free = buff_out - buff_in;
  53         return bytes_free;
  54 }
  55
  56 int synth_buffer_empty(void)
  57 {
  58         return (buff_in == buff_out);
  59 }
  60 EXPORT_SYMBOL_GPL(synth_buffer_empty);
  61
  62 void synth_buffer_add(char ch)
  63 {
  64         if (!synth->alive) {
  65                 /* This makes sure that we won't stop TTYs if there is no synth
  66                  * to restart them */
  67                 return;
  68         }
  69         if (synth_buffer_free() <= 100) {
  70                 synth_start();
  71                 speakup_stop_ttys();
  72         }
  73         if (synth_buffer_free() <= 1)
  74                 return;
  75         *buff_in++ = ch;
  76         if (buff_in > buffer_end)
  77                 buff_in = synth_buffer;
  78 }
  79
  80 char synth_buffer_getc(void)
  81 {
  82         char ch;
  83
  84         if (buff_out == buff_in)
  85                 return 0;
  86         ch = *buff_out++;
  87         if (buff_out > buffer_end)
  88                 buff_out = synth_buffer;
  89         return ch;
  90 }
  91 EXPORT_SYMBOL_GPL(synth_buffer_getc);
  92
  93 char synth_buffer_peek(void)
  94 {
  95         if (buff_out == buff_in)
  96                 return 0;
  97         return *buff_out;
  98 }
  99 EXPORT_SYMBOL_GPL(synth_buffer_peek);
 100
 101 void synth_buffer_clear(void)
 102 {
 103         buff_in = buff_out = synth_buffer;
 104         return;
 105 }
 106 EXPORT_SYMBOL_GPL(synth_buffer_clear);