1 files changed, 77 insertions, 0 deletions
diff --git a/common/debug.c b/common/debug.c
new file mode 100644
index 0000000..be71cd2
--- /dev/null
+++ b/common/debug.c
@@ -0,0 +1,77 @@
+#include <apos/types.h>
+#include <apos/debug.h>
+
+#ifdef DEBUG
+
+/* if there arises a need for more supported serial drivers, I should probably
+ * try to implement some kind of basic driver subsystem, but this is good enough
+ * for now. */
+
+struct __packed ns16550a {
+	union {
+		struct {
+			uint8_t data;
+			uint8_t irq;
+		};
+
+		struct {
+			uint8_t lsbr;
+			uint8_t msbr;
+		};
+	};
+
+	uint8_t irq_id;
+	uint8_t lcr;
+	uint8_t mcr;
+	uint8_t lsr;
+	uint8_t msr;
+	uint8_t scr;
+};
+
+#define LSR_DR   (1 << 0)
+#define LSR_OE   (1 << 1)
+#define LSR_PE   (1 << 2)
+#define LSR_FE   (1 << 3)
+#define LSR_BI   (1 << 4)
+#define LSR_THRE (1 << 5)
+#define LSR_TEMT (1 << 6)
+#define LSR_ERR  (1 << 7)
+
+static struct ns16550a *port = 0;
+
+int __serial_tx_empty()
+{
+	return port->lsr & LSR_THRE;
+}
+
+void __serial_putchar(char c)
+{
+	if (!port)
+		return;
+
+	while(__serial_tx_empty() == 0);
+
+	port->data = c;
+}
+
+void dbg_init(void *pt, enum serial_dev_t dev)
+{
+	switch (dev) {
+		case NS16550A:
+			port = pt;
+			break;
+	}
+
+	/* in the future possibly configure the serial connection, though the
+	 * defaults (set by U-boot) seem to work alright */
+}
+
+void dbg(const char *fmt, ...)
+{
+	/* do a proper implementation later, for now just dump stuff */
+	while(*fmt){
+		__serial_putchar(*fmt++);
+	}
+}
+
+#endif /* DEBUG */