drivers/serial/sandbox.c

   1 /*
   2  * Copyright (c) 2011 The Chromium OS Authors.
   3  *
   4  * SPDX-License-Identifier:     GPL-2.0+
   5  */
   6
   7 /*
   8  * This provide a test serial port. It provides an emulated serial port where
   9  * a test program and read out the serial output and inject serial input for
  10  * U-Boot.
  11  */
  12
  13 #include <common.h>
  14 #include <lcd.h>
  15 #include <os.h>
  16 #include <serial.h>
  17 #include <linux/compiler.h>
  18
  19 /*
  20  *
  21  *   serial_buf: A buffer that holds keyboard characters for the
  22  *               Sandbox U-boot.
  23  *
  24  * invariants:
  25  *   serial_buf_write            == serial_buf_read -> empty buffer
  26  *   (serial_buf_write + 1) % 16 == serial_buf_read -> full buffer
  27  */
  28 static char serial_buf[16];
  29 static unsigned int serial_buf_write;
  30 static unsigned int serial_buf_read;
  31
  32 static int sandbox_serial_init(void)
  33 {
  34         os_tty_raw(0);
  35         return 0;
  36 }
  37
  38 static void sandbox_serial_setbrg(void)
  39 {
  40 }
  41
  42 static void sandbox_serial_putc(const char ch)
  43 {
  44         os_write(1, &ch, 1);
  45 }
  46
  47 static void sandbox_serial_puts(const char *str)
  48 {
  49         os_write(1, str, strlen(str));
  50 }
  51
  52 static unsigned int increment_buffer_index(unsigned int index)
  53 {
  54         return (index + 1) % ARRAY_SIZE(serial_buf);
  55 }
  56
  57 static int sandbox_serial_tstc(void)
  58 {
  59         const unsigned int next_index =
  60                 increment_buffer_index(serial_buf_write);
  61         ssize_t count;
  62
  63         os_usleep(100);
  64 #ifdef CONFIG_LCD
  65         lcd_sync();
  66 #endif
  67         if (next_index == serial_buf_read)
  68                 return 1;       /* buffer full */
  69
  70         count = os_read_no_block(0, &serial_buf[serial_buf_write], 1);
  71         if (count == 1)
  72                 serial_buf_write = next_index;
  73         return serial_buf_write != serial_buf_read;
  74 }
  75
  76 static int sandbox_serial_getc(void)
  77 {
  78         int result;
  79
  80         while (!sandbox_serial_tstc())
  81                 ;       /* buffer empty */
  82
  83         result = serial_buf[serial_buf_read];
  84         serial_buf_read = increment_buffer_index(serial_buf_read);
  85         return result;
  86 }
  87
  88 static struct serial_device sandbox_serial_drv = {
  89         .name   = "sandbox_serial",
  90         .start  = sandbox_serial_init,
  91         .stop   = NULL,
  92         .setbrg = sandbox_serial_setbrg,
  93         .putc   = sandbox_serial_putc,
  94         .puts   = sandbox_serial_puts,
  95         .getc   = sandbox_serial_getc,
  96         .tstc   = sandbox_serial_tstc,
  97 };
  98
  99 void sandbox_serial_initialize(void)
 100 {
 101         serial_register(&sandbox_serial_drv);
 102 }
 103
 104 __weak struct serial_device *default_serial_console(void)
 105 {
 106         return &sandbox_serial_drv;
 107 }