drivers/accessibility/speakup/buffers.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/console.h>
   3 #include <linux/types.h>
   4 #include <linux/wait.h>
   5
   6 #include "speakup.h"
   7 #include "spk_priv.h"
   8
   9 #define SYNTH_BUF_SIZE 8192     /* currently 8K bytes */
  10
  11 static u16 synth_buffer[SYNTH_BUF_SIZE];        /* guess what this is for! */
  12 static u16 *buff_in = synth_buffer;
  13 static u16 *buff_out = synth_buffer;
  14 static u16 *buffer_end = synth_buffer + SYNTH_BUF_SIZE - 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 && vc_cons[i].d->port.tty)
  32                         start_tty(vc_cons[i].d->port.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 && vc_cons[i].d->port.tty)
  43                         stop_tty(vc_cons[i].d->port.tty);
  44 }
  45
  46 static int synth_buffer_free(void)
  47 {
  48         int chars_free;
  49
  50         if (buff_in >= buff_out)
  51                 chars_free = SYNTH_BUF_SIZE - (buff_in - buff_out);
  52         else
  53                 chars_free = buff_out - buff_in;
  54         return chars_free;
  55 }
  56
  57 int synth_buffer_empty(void)
  58 {
  59         return (buff_in == buff_out);
  60 }
  61 EXPORT_SYMBOL_GPL(synth_buffer_empty);
  62
  63 void synth_buffer_add(u16 ch)
  64 {
  65         if (!synth->alive) {
  66                 /* This makes sure that we won't stop TTYs if there is no synth
  67                  * to restart them
  68                  */
  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         /* We have written something to the speech synthesis, so we are not
  81          * paused any more.
  82          */
  83         spk_paused = false;
  84 }
  85
  86 u16 synth_buffer_getc(void)
  87 {
  88         u16 ch;
  89
  90         if (buff_out == buff_in)
  91                 return 0;
  92         ch = *buff_out++;
  93         if (buff_out > buffer_end)
  94                 buff_out = synth_buffer;
  95         return ch;
  96 }
  97 EXPORT_SYMBOL_GPL(synth_buffer_getc);
  98
  99 u16 synth_buffer_peek(void)
 100 {
 101         if (buff_out == buff_in)
 102                 return 0;
 103         return *buff_out;
 104 }
 105 EXPORT_SYMBOL_GPL(synth_buffer_peek);
 106
 107 void synth_buffer_skip_nonlatin1(void)
 108 {
 109         while (buff_out != buff_in) {
 110                 if (*buff_out < 0x100)
 111                         return;
 112                 buff_out++;
 113                 if (buff_out > buffer_end)
 114                         buff_out = synth_buffer;
 115         }
 116 }
 117 EXPORT_SYMBOL_GPL(synth_buffer_skip_nonlatin1);
 118
 119 void synth_buffer_clear(void)
 120 {
 121         buff_in = synth_buffer;
 122         buff_out = synth_buffer;
 123 }
 124 EXPORT_SYMBOL_GPL(synth_buffer_clear);