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 <os.h>
  15 #include <serial.h>
  16 #include <linux/compiler.h>
  17
  18 /*
  19  *
  20  *   serial_buf: A buffer that holds keyboard characters for the
  21  *               Sandbox U-boot.
  22  *
  23  * invariants:
  24  *   serial_buf_write            == serial_buf_read -> empty buffer
  25  *   (serial_buf_write + 1) % 16 == serial_buf_read -> full buffer
  26  */
  27 static char serial_buf[16];
  28 static unsigned int serial_buf_write;
  29 static unsigned int serial_buf_read;
  30
  31 static int sandbox_serial_init(void)
  32 {
  33         os_tty_raw(0);
  34         return 0;
  35 }
  36
  37 static void sandbox_serial_setbrg(void)
  38 {
  39 }
  40
  41 static void sandbox_serial_putc(const char ch)
  42 {
  43         os_write(1, &ch, 1);
  44 }
  45
  46 static void sandbox_serial_puts(const char *str)
  47 {
  48         os_write(1, str, strlen(str));
  49 }
  50
  51 static unsigned int increment_buffer_index(unsigned int index)
  52 {
  53         return (index + 1) % ARRAY_SIZE(serial_buf);
  54 }
  55
  56 static int sandbox_serial_tstc(void)
  57 {
  58         const unsigned int next_index =
  59                 increment_buffer_index(serial_buf_write);
  60         ssize_t count;
  61
  62         os_usleep(100);
  63         if (next_index == serial_buf_read)
  64                 return 1;       /* buffer full */
  65
  66         count = os_read_no_block(0, &serial_buf[serial_buf_write], 1);
  67         if (count == 1)
  68                 serial_buf_write = next_index;
  69         return serial_buf_write != serial_buf_read;
  70 }
  71
  72 static int sandbox_serial_getc(void)
  73 {
  74         int result;
  75
  76         while (!sandbox_serial_tstc())
  77                 ;       /* buffer empty */
  78
  79         result = serial_buf[serial_buf_read];
  80         serial_buf_read = increment_buffer_index(serial_buf_read);
  81         return result;
  82 }
  83
  84 static struct serial_device sandbox_serial_drv = {
  85         .name   = "sandbox_serial",
  86         .start  = sandbox_serial_init,
  87         .stop   = NULL,
  88         .setbrg = sandbox_serial_setbrg,
  89         .putc   = sandbox_serial_putc,
  90         .puts   = sandbox_serial_puts,
  91         .getc   = sandbox_serial_getc,
  92         .tstc   = sandbox_serial_tstc,
  93 };
  94
  95 void sandbox_serial_initialize(void)
  96 {
  97         serial_register(&sandbox_serial_drv);
  98 }
  99
 100 __weak struct serial_device *default_serial_console(void)
 101 {
 102         return &sandbox_serial_drv;
 103 }