driver/serial: Serial write interface

driver/irq/pic/serial/serial.c

@@ -0,0 +1,55 @@
+
+#include "serial.h"
+#include "../internal.h"
+#include "../../../../interrupt/interrupt.h"
+
+
+pic_serial_Port pic_serial_COM1 = {0x3f8, false}, pic_serial_COM2 = {0x2f8, false};
+
+bool pic_serial_Init(pic_serial_Port *port, int baudrate, int lineFlags) {
+	if (115200 % baudrate != 0)
+		return false;
+
+	uint16_t divisor = 115200 / baudrate;
+	INTERRUPT_DISABLE;
+
+	outb(port->port + 3, 0x80);           // Enable DLAB (set baud rate divisor)
+	outb(port->port + 0, divisor & 0xFF); // Set divisor (lo byte)
+	outb(port->port + 1, divisor >> 8);   //             (hi byte)
+	outb(port->port + 3, 0x03);           // 8 bits, no parity, one stop bit
+	outb(port->port + 2, 0xC7);           // Enable FIFO, clear them, with 14-byte threshold
+	outb(port->port + 4, 0x0B);           // IRQs enabled, RTS/DSR set
+	outb(port->port + 4, 0x1E);           // Set in loopback mode, test the serial chip
+	outb(port->port + 0, 0xAE);           // Test serial chip (send byte 0xAE and check if serial returns same byte)
+
+	// Check if serial is faulty (i.e: not same byte as sent)
+	if (inb(port->port + 0) != 0xAE) {
+		INTERRUPT_RESTORE;
+		return false;
+	}
+
+	// If serial is not faulty set it in normal operation mode
+	// (not-loopback with IRQs enabled and OUT#1 and OUT#2 bits enabled)
+	outb(port->port + 4, 0x0F);
+	port->ok = true;
+
+	INTERRUPT_RESTORE;
+	return true;
+}
+
+void pic_serial_Write(pic_serial_Port *port, const char *str, int n) {
+	if (port && port->ok) {
+		if (n != 0) {
+			for (int i = 0; i < n; i++) {
+				while ((inb(port->port + 5) & 0x20) == 0) {}
+				outb(port->port, str[i]);
+			}
+		} else {
+			while (*str != 0) {
+				while ((inb(port->port + 5) & 0x20) == 0) {}
+				outb(port->port, *str);
+				str++;
+			}
+		}
+	}
+}

driver/irq/pic/serial/serial.h

@@ -0,0 +1,33 @@
+#pragma once
+
+#include "stdbool.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+// Serial port state.
+//
+// Line protocol defaults to 8N1 (8 bits, no parity, one stop bit)
+typedef struct {
+	int  port; // IO Port
+	bool ok;   // Is the port usable?
+} pic_serial_Port;
+
+extern pic_serial_Port pic_serial_COM1, pic_serial_COM2;
+
+// Init initializes a serial port. Returns true if success.
+//
+// TODO lineFlags is ignored by now, always 8N1
+bool pic_serial_Init(pic_serial_Port *port, int baudrate, int lineFlags);
+
+// Write writes a string to a serial port, if the port is usable.
+//
+// Writes n chars. If n is 0, writes until it reaches NUL.
+void pic_serial_Write(pic_serial_Port *port, const char *str, int n);
+
+
+#ifdef __cplusplus
+}
+#endif