From: Taylor Hutt thutt@chromium.org
Implements the tstc() interface for the serial driver. Multiplexing the console between the serial port and a keyboard uses a polling method of checking if characters are available; this means that the serial console must be non-blocking when attempting to read characters.
Signed-off-by: Taylor Hutt thutt@chromium.org Signed-off-by: Simon Glass sjg@chromium.org --- Changes in v3: None Changes in v2: None
arch/sandbox/cpu/os.c | 8 ++++++++ drivers/serial/sandbox.c | 44 ++++++++++++++++++++++++++++++++++++++------ include/os.h | 10 ++++++++++ 3 files changed, 56 insertions(+), 6 deletions(-)
diff --git a/arch/sandbox/cpu/os.c b/arch/sandbox/cpu/os.c index 36637af..3e37c93 100644 --- a/arch/sandbox/cpu/os.c +++ b/arch/sandbox/cpu/os.c @@ -44,6 +44,14 @@ ssize_t os_read(int fd, void *buf, size_t count) return read(fd, buf, count); }
+ssize_t os_read_no_block(int fd, void *buf, size_t count) +{ + const int flags = fcntl(fd, F_GETFL, 0); + + fcntl(fd, F_SETFL, flags | O_NONBLOCK); + return os_read(fd, buf, count); +} + ssize_t os_write(int fd, const void *buf, size_t count) { return write(fd, buf, count); 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 = { diff --git a/include/os.h b/include/os.h index 699682a..c452d1b 100644 --- a/include/os.h +++ b/include/os.h @@ -40,6 +40,16 @@ struct sandbox_state; ssize_t os_read(int fd, void *buf, size_t count);
/** + * Access to the OS read() system call with non-blocking access + * + * \param fd File descriptor as returned by os_open() + * \param buf Buffer to place data + * \param count Number of bytes to read + * \return number of bytes read, or -1 on error + */ +ssize_t os_read_no_block(int fd, void *buf, size_t count); + +/** * Access to the OS write() system call * * \param fd File descriptor as returned by os_open()