subsystem: console: tty init checks and support for polled-only devices

This patch add tty runtime initialization check for console support
routines. Without it callers of routines API are not aware that
initialization of tty was failed. This patch basically checks
availability of console device and also its support for
interrupt driven transfers if routines are configured to use it.

Signed-off-by: Pavel Kral <pavel.kral@omsquare.com>

include/console/console.h

@@ -23,9 +23,9 @@ extern "C" {
  *  and incompatible with, callback (push-style) console handling
  *  (via console_input_fn callback, etc.).
  *
- *  @return N/A
+ * @return 0 on success, error code (<0) otherwise
  */
-void console_init(void);
+int console_init(void);
 
 /**
  * @brief Read data from console.

subsys/console/getchar.c

@@ -8,6 +8,7 @@
 #include <device.h>
 #include <console/console.h>
 #include <console/tty.h>
+#include <uart.h>
 
 static struct tty_serial console_serial;
 
@@ -46,12 +47,29 @@ int console_getchar(void)
 	return c;
 }
 
-void console_init(void)
+int console_init(void)
 {
 	struct device *uart_dev;
+	int ret;
 
 	uart_dev = device_get_binding(CONFIG_UART_CONSOLE_ON_DEV_NAME);
-	tty_init(&console_serial, uart_dev);
+	ret = tty_init(&console_serial, uart_dev);
+
+	if (ret) {
+		return ret;
+	}
+
+	/* Checks device driver supports for interrupt driven data transfers. */
+	if (CONFIG_CONSOLE_GETCHAR_BUFSIZE + CONFIG_CONSOLE_PUTCHAR_BUFSIZE) {
+		const struct uart_driver_api *api =
+			(const struct uart_driver_api *)uart_dev->driver_api;
+		if (!api->irq_callback_set) {
+			return -ENOTSUP;
+		}
+	}
+
 	tty_set_tx_buf(&console_serial, console_txbuf, sizeof(console_txbuf));
 	tty_set_rx_buf(&console_serial, console_rxbuf, sizeof(console_rxbuf));
+
+	return 0;
 }

subsys/console/tty.c

@@ -238,6 +238,10 @@ ssize_t tty_read(struct tty_serial *tty, void *buf, size_t size)
 
 int tty_init(struct tty_serial *tty, struct device *uart_dev)
 {
+	if (!uart_dev) {
+		return -ENODEV;
+	}
+
 	tty->uart_dev = uart_dev;
 
 	/* We start in unbuffer mode. */