Mon 14 Oct 23:06:38 CEST 2024

kernel/serial.c

@@ -0,0 +1,162 @@
+/*
+Copyright (C) 2016-2019 The University of Notre Dame
+This software is distributed under the GNU General Public License.
+See the file LICENSE for details.
+*/
+
+// Derived from: https://wiki.osdev.org/Serial_Ports#Example_Code
+// For more info:
+//     https://wiki.osdev.org/Serial_Ports
+//     http://www.webcitation.org/5ugQv5JOw
+
+#include "kernel/types.h"
+#include "ioports.h"
+#include "string.h"
+#include "device.h"
+
+#define COM1 0x3f8
+#define COM2 0x2F8
+#define COM3 0x3E8
+#define COM4 0x2E8
+
+#define SERIAL_DATA 0		// If DLAB disabled in LCR
+
+#define SERIAL_IRQ_ENABLE 1	// If DLAB disabled in LCR
+#define SERIAL_IRQ_DATA_AVAILABILE (0x01 << 0)
+#define SERIAL_IRQ_TRASMITTER_EMPTY (0x01 << 1)
+#define SERIAL_IRQ_ERROR (0x01 << 2)
+#define SERIAL_IRQ_STATUS_CHANGE (0x01 << 3)
+
+#define SERIAL_DIVISOR_LO 0	// If DLAB enabled in LCR
+
+#define SERIAL_DIVISOR_HI 1	// If DLAB enabled in LCR
+
+#define SERIAL_FCR 2
+#define SERIAL_FIFO_ENABLE (0x01 << 0)
+#define SERIAL_FIFO_CLEAR_RECIEVER (0x01 << 1)
+#define SERIAL_FIFO_CLEAR_TRANSMITTER (0x01 << 2)
+#define SERIAL_FIFO_DMA_MODE (0x01 << 3)
+#define SERIAL_TRIGGER_LEVEL0 (0x01 << 6)
+#define SERIAL_TRIGGER_LEVEL1 (0x01 << 7)
+
+#define SERIAL_LCR 3
+#define SERIAL_CHARLEN_START (0x01 << 0)
+#define SERIAL_STOP_BITS (0x01 << 2)
+#define SERIAL_DLAB_ENABLE (0x01 << 3)
+
+#define SERIAL_MCR 4
+#define SERIAL_DATA_TERMINAL_READY (0x01 << 0)
+#define SERIAL_REQUEST_TO_SEND (0x01 << 1)
+#define SERIAL_AUX_OUT1 (0x01 << 2)
+#define SERIAL_AUX_OUT2 (0x01 << 3)
+
+#define SERIAL_LSR 5
+#define SERIAL_DATA_AVAILABLE (0x01 << 0)
+#define SERIAL_TRANSMIT_EMPTY (0x01 << 5)
+
+#define SERIAL_MSR 6
+
+#define SERIAL_SCRATCH 7
+
+static const int serial_ports[4] = { COM1, COM2, COM3, COM4 };
+
+static void serial_init_port(int port)
+{
+	//Disable iterrupts
+	outb(0x00, port + SERIAL_IRQ_ENABLE);
+	//Enable DLAB(set baud rate divisor)
+	outb(SERIAL_DLAB_ENABLE, port + SERIAL_LCR);
+	//Set divisor to 3(lo byte) 38400 baud
+	outb(0x03, port + SERIAL_DIVISOR_LO);
+	//(hi byte)
+	outb(0x00, port + SERIAL_DIVISOR_HI);
+	//8 bits, no parity, one stop bit
+	outb(SERIAL_CHARLEN_START * 3, port + SERIAL_LCR);
+	//Enable FIFO, clear them, with 14 - byte threshold
+	outb(SERIAL_FIFO_ENABLE | SERIAL_FIFO_CLEAR_RECIEVER | SERIAL_FIFO_CLEAR_TRANSMITTER | SERIAL_TRIGGER_LEVEL0 | SERIAL_TRIGGER_LEVEL1, port + SERIAL_FCR);
+	//IRQs enabled, RTS / DSR set
+	outb(SERIAL_DATA_TERMINAL_READY | SERIAL_REQUEST_TO_SEND | SERIAL_AUX_OUT2, port + SERIAL_MCR);
+}
+
+static int serial_received(int port)
+{
+	return inb(port + SERIAL_LSR) & SERIAL_DATA_AVAILABLE;
+}
+
+static int is_transmit_empty(int port)
+{
+	return inb(port + SERIAL_LSR) & SERIAL_TRANSMIT_EMPTY;
+}
+
+static int is_valid_port(uint8_t port_no)
+{
+	return port_no < sizeof(serial_ports) / sizeof(int);
+}
+
+char serial_read(uint8_t port_no)
+{
+	if(!is_valid_port(port_no))
+		return -1;
+
+	while(serial_received(serial_ports[port_no]) == 0);
+	return inb(serial_ports[port_no]);
+}
+
+int serial_write(uint8_t port_no, char a)
+{
+	if(!is_valid_port(port_no))
+		return -1;
+
+	while(is_transmit_empty(serial_ports[port_no]) == 0);
+	outb(a, serial_ports[port_no]);
+	return 0;
+}
+
+int serial_device_probe( int unit, int *blocksize, int *nblocks, char *info )
+{
+	if(unit<0 || unit>3) return 0;
+	serial_init_port(serial_ports[unit]);
+	*blocksize = 1;
+	*nblocks = 0;
+	strcpy(info,"serial");
+	return 1;
+}
+
+int serial_device_read( int unit, void *data, int length, int offset )
+{
+	int i;
+	char *cdata = data;
+	for(i=0;i<length;i++) {
+		cdata[i] = serial_read(unit);
+	}
+	return length;
+}
+
+int serial_device_write( int unit, const void *data, int length, int offset )
+{
+	int i;
+	const char *cdata = data;
+	for(i=0;i<length;i++) {
+		serial_write(unit,cdata[i]);
+	}
+	return length;
+}
+
+static struct device_driver serial_driver = {
+       .name           = "serial",
+       .probe          = serial_device_probe,
+       .read           = serial_device_read,
+       .read_nonblock  = serial_device_read,
+       .write          = serial_device_write
+};
+
+void serial_init()
+{
+	int i;
+	for(i = 0; i < sizeof(serial_ports) / sizeof(int); i++) {
+		serial_init_port(serial_ports[i]);
+	}
+	device_driver_register(&serial_driver);
+}
+
+