diff options
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/serial/sandbox.c | 44 |
1 files changed, 38 insertions, 6 deletions
diff --git a/drivers/serial/sandbox.c b/drivers/serial/sandbox.c index cb19401..b73520c 100644 --- a/drivers/serial/sandbox.c +++ b/drivers/serial/sandbox.c @@ -30,6 +30,19 @@ #include <serial.h> #include <linux/compiler.h> +/* + * + * serial_buf: A buffer that holds keyboard characters for the + * Sandbox U-boot. + * + * invariants: + * serial_buf_write == serial_buf_read -> empty buffer + * (serial_buf_write + 1) % 16 == serial_buf_read -> full buffer + */ +static char serial_buf[16]; +static unsigned int serial_buf_write; +static unsigned int serial_buf_read; + static int sandbox_serial_init(void) { os_tty_raw(0); @@ -50,18 +63,37 @@ static void sandbox_serial_puts(const char *str) os_write(1, str, strlen(str)); } -static int sandbox_serial_getc(void) +static unsigned int increment_buffer_index(unsigned int index) +{ + return (index + 1) % ARRAY_SIZE(serial_buf); +} + +static int sandbox_serial_tstc(void) { - char buf; + const unsigned int next_index = + increment_buffer_index(serial_buf_write); ssize_t count; - count = os_read(0, &buf, 1); - return count == 1 ? buf : 0; + os_usleep(100); + if (next_index == serial_buf_read) + return 1; /* buffer full */ + + count = os_read_no_block(0, &serial_buf[serial_buf_write], 1); + if (count == 1) + serial_buf_write = next_index; + return serial_buf_write != serial_buf_read; } -static int sandbox_serial_tstc(void) +static int sandbox_serial_getc(void) { - return 0; + int result; + + while (!sandbox_serial_tstc()) + ; /* buffer empty */ + + result = serial_buf[serial_buf_read]; + serial_buf_read = increment_buffer_index(serial_buf_read); + return result; } static struct serial_device sandbox_serial_drv = { |