Message queue and work item for process scan events.

* Prep for using ISR for kscan GPIO, by moving event
  process into a work item.

Kconfig

@@ -0,0 +1,7 @@
+mainmenu "ZMK Firmware"
+
+config ZMK_KSCAN_EVENT_QUEUE_SIZE
+	int "Size of the event queue for KSCAN events to buffer events"
+	default 4
+
+source "Kconfig.zephyr"

src/kscan.c

@@ -6,24 +6,61 @@
 
 #include <zephyr.h>
 #include <device.h>
-#include <devicetree.h>
 #include <drivers/kscan.h>
+#include <logging/log.h>
 
-static void zmk_kscan_callback(struct device *dev, u32_t row, u32_t column, bool pressed) {
-	printk("Row: %d, col: %d, pressed: %s\n", row, column, (pressed ? "true" : "false"));
-	// TODO: Push this to a message box, and then trigger a work item!
+LOG_MODULE_REGISTER(zmk_kscan, CONFIG_ZMK_KSCAN_LOG_LEVEL);
+
+#define ZMK_KSCAN_EVENT_STATE_PRESSED 0
+#define ZMK_KSCAN_EVENT_STATE_RELEASED 1
+
+struct zmk_kscan_event {
+	u32_t row;
+	u32_t column;
+	u32_t state;
+};
+
+struct zmk_kscan_msg_processor {
+	struct k_work work;
+} msg_processor;
+
+K_MSGQ_DEFINE(zmk_kscan_msgq, sizeof(struct zmk_kscan_event), CONFIG_ZMK_KSCAN_EVENT_QUEUE_SIZE, 4);
+
+static void zmk_kscan_callback(struct device *dev, u32_t row, u32_t column, bool pressed)
+{
+	struct zmk_kscan_event ev = {
+		.row = row,
+		.column = column,
+		.state = (pressed ? ZMK_KSCAN_EVENT_STATE_PRESSED : ZMK_KSCAN_EVENT_STATE_RELEASED)
+	};
+
+	k_msgq_put(&zmk_kscan_msgq, &ev, K_NO_WAIT);
+	k_work_submit(&msg_processor.work);
 }
 
-int zmk_kscan_init(char* name) {
+void zmk_kscan_process_msgq(struct k_work *item)
+{
+	struct zmk_kscan_event ev;
+	printk("process messages!\n");
+
+	while(k_msgq_get(&zmk_kscan_msgq, &ev, K_NO_WAIT) == 0) {
+		bool pressed = (ev.state == ZMK_KSCAN_EVENT_STATE_PRESSED);
+		printk("Row: %d, col: %d, pressed: %s\n", ev.row, ev.column, (pressed ? "true" : "false"));
+	}
+}
+
+int zmk_kscan_init(char* name)
+{
 	struct device *dev = device_get_binding(name);
 	if (dev == NULL) {
-		printk("NO DEVICE!\n");
+		LOG_ERR("Failed to get the KSCAN device");
 		return -EINVAL;
 	}
 
 	return 0;
 
-	kscan_config(dev, zmk_kscan_callback);
+	k_work_init(&msg_processor.work, zmk_kscan_process_msgq);
 
+	kscan_config(dev, zmk_kscan_callback);
 	kscan_enable_callback(dev);
 }

src/kscan.h

@@ -1,2 +1,6 @@
+#ifndef ZMK_KSCAN_H
+#define ZMK_KSCAN_H
 
 int zmk_kscan_init(char *name);
+
+#endif