Add UART irq input hook to uart_console_isr()

Adds an input hook to be used by the interrupt handler uart_console_isr().
This hook permits the console input to detect a character escape sequence
that can be used to override the console's default input behavior.

This input hook can be set using the following API:
   void uart_irq_input_hook_set(struct device *dev,
                                int (*hook)(struct device *, uint8_t));

The hook returns 1 if the handler should stop processing the character,
and 0 if it should not stop.

Change-Id: I95e7da75e07fb6caaca2d45e80bfc4334a43c0ac
Signed-off-by: Peter Mitsis <peter.mitsis@windriver.com>

drivers/console/uart_console.c

@@ -136,6 +136,18 @@ void uart_console_isr(void *unused)
 			uint8_t byte;
 			int rx;
 
+			rx = read_uart(UART_CONSOLE_DEV, &byte, 1);
+			if (rx < 0) {
+				return;
+			}
+
+			if (uart_irq_input_hook(UART_CONSOLE_DEV, byte) != 0) {
+				/*
+				 * The input hook indicates that no further processing
+				 * should be done by this handler.
+				 */
+				return;
+			}
 
 			if (!cmd) {
 				cmd = nano_isr_fifo_get(avail_queue);
@@ -143,12 +155,6 @@ void uart_console_isr(void *unused)
 					return;
 			}
 
-			rx = read_uart(UART_CONSOLE_DEV, &byte, 1);
-			if (rx < 0) {
-				nano_isr_fifo_put(avail_queue, cmd);
-				return;
-			}
-
 			/* Echo back to console */
 			uart_poll_out(UART_CONSOLE_DEV, byte);
 

include/uart.h

@@ -106,6 +106,7 @@ struct uart_driver_api {
 	int (*irq_is_pending)(struct device *dev);
 	int (*irq_update)(struct device *dev);
 	unsigned int (*irq_get)(struct device *dev);
+	int (*irq_input_hook)(struct device *dev, uint8_t byte);
 
 #endif
 };
@@ -416,6 +417,51 @@ static inline unsigned int uart_irq_get(struct device *dev)
 	return 0;
 }
 
+/**
+ * @brief Invoke the UART input hook routine if installed
+ *
+ * The input hook is a custom handler invoked by the ISR on each received
+ * character.  It allows the detection of a character escape sequence that may
+ * be used to override the behavior of the ISR handler.
+ *
+ * @param dev UART device struct (of type struct uart_device_config_t)
+ * @param byte Byte to process
+ *
+ * @return 1 if character processing must stop, 0 or if it is to continue
+ */
+static inline int uart_irq_input_hook(struct device *dev, uint8_t byte)
+{
+	struct uart_driver_api *api;
+
+	api = (struct uart_driver_api *)dev->driver_api;
+
+	if ((api != NULL) && (api->irq_input_hook != NULL)) {
+		return api->irq_input_hook(dev, byte);
+	}
+
+	return 0;
+}
+
+/**
+ * @brief Set the UART input hook routine
+ *
+ * @param dev UART device struct (of type struct uart_device_config_t)
+ * @param hook Routine to use as UART input hook
+ *
+ * @return N/A
+ */
+static inline void uart_irq_input_hook_set(struct device *dev,
+		int (*hook)(struct device *, uint8_t))
+{
+	struct uart_driver_api *api;
+
+	api = (struct uart_driver_api *)dev->driver_api;
+
+	if (api != NULL) {
+		api->irq_input_hook = hook;
+	}
+}
+
 #endif
 
 #ifdef __cplusplus