drivers/staging/speakup/buffers.c

   1 #include <linux/console.h>
   2 #include <linux/smp_lock.h>
   3 #include <linux/types.h>
   4 #include <linux/wait.h>
   5
   6 #include "speakup.h"
   7 #include "spk_priv.h"
   8
   9 #define synthBufferSize 8192    /* currently 8K bytes */
  10
  11 static u_char synth_buffer[synthBufferSize];    /* guess what this is for! */
  12 static u_char *buff_in = synth_buffer;
  13 static u_char *buff_out = synth_buffer;
  14 static u_char *buffer_end = synth_buffer+synthBufferSize-1;
  15
  16 /* These try to throttle applications by stopping the TTYs
  17  * Note: we need to make sure that we will restart them eventually, which is
  18  * usually not possible to do from the notifiers. TODO: it should be possible
  19  * starting from linux 2.6.26.
  20  *
  21  * So we only stop when we know alive == 1 (else we discard the data anyway),
  22  * and the alive synth will eventually call start_ttys from the thread context.
  23  */
  24 void speakup_start_ttys(void)
  25 {
  26         int i;
  27
  28         for (i = 0; i < MAX_NR_CONSOLES; i++) {
  29                 if (speakup_console[i] && speakup_console[i]->tty_stopped)
  30                         continue;
  31                 if ((vc_cons[i].d != NULL) && (vc_cons[i].d->vc_tty != NULL))
  32                         start_tty(vc_cons[i].d->vc_tty);
  33         }
  34 }
  35 EXPORT_SYMBOL_GPL(speakup_start_ttys);
  36
  37 static void speakup_stop_ttys(void)
  38 {
  39         int i;
  40
  41         for (i = 0; i < MAX_NR_CONSOLES; i++)
  42                 if ((vc_cons[i].d != NULL) && (vc_cons[i].d->vc_tty != NULL))
  43                         stop_tty(vc_cons[i].d->vc_tty);
  44         return;
  45 }
  46
  47 static int synth_buffer_free(void)
  48 {
  49         int bytesFree;
  50
  51         if (buff_in >= buff_out)
  52                 bytesFree = synthBufferSize - (buff_in - buff_out);
  53         else
  54                 bytesFree = buff_out - buff_in;
  55         return bytesFree;
  56 }
  57
  58 int synth_buffer_empty(void)
  59 {
  60         return (buff_in == buff_out);
  61 }
  62 EXPORT_SYMBOL_GPL(synth_buffer_empty);
  63
  64 void synth_buffer_add(char ch)
  65 {
  66         if (!synth->alive) {
  67                 /* This makes sure that we won't stop TTYs if there is no synth
  68                  * to restart them */
  69                 return;
  70         }
  71         if (synth_buffer_free() <= 100) {
  72                 synth_start();
  73                 speakup_stop_ttys();
  74         }
  75         if (synth_buffer_free() <= 1)
  76                 return;
  77         *buff_in++ = ch;
  78         if (buff_in > buffer_end)
  79                 buff_in = synth_buffer;
  80 }
  81
  82 char synth_buffer_getc(void)
  83 {
  84         char ch;
  85
  86         if (buff_out == buff_in)
  87                 return 0;
  88         ch = *buff_out++;
  89         if (buff_out > buffer_end)
  90                 buff_out = synth_buffer;
  91         return ch;
  92 }
  93 EXPORT_SYMBOL_GPL(synth_buffer_getc);
  94
  95 char synth_buffer_peek(void)
  96 {
  97         if (buff_out == buff_in)
  98                 return 0;
  99         return *buff_out;
 100 }
 101 EXPORT_SYMBOL_GPL(synth_buffer_peek);
 102
 103 void synth_buffer_clear(void)
 104 {
 105         buff_in = buff_out = synth_buffer;
 106         return;
 107 }
 108 EXPORT_SYMBOL_GPL(synth_buffer_clear);