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#include "uart.h"
#include <stddef.h>
#include <sys/io.h>
enum uart_16550_offset {
Data = 0, // read from receive buffer / write to transmit buffer | BaudDiv_l
InterruptControl = 1, // interrupt enable | BaudDiv_h
FifoControl = 2, // interrupt ID and FIFO control
LineControl = 3, // most significant bit is the DLAB
ModemControl = 4,
LineStatus = 5,
ModemStatus = 6,
Scratch = 7,
};
// Line Control
// | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
// |dla| | parity | s | data |
enum LineControl {
d5bit = 0x00, // 0000 0000 data bits
d6bit = 0x01, // 0000 0001
d7bit = 0x02, // 0000 0010
d8bit = 0x03, // 0000 0011
// none = 0b00000000, // parity bits
odd = 0x08, // 0000 1000
even = 0x18, // 0001 1000
mark = 0x28, // 0010 1000
space = 0x38, // 0011 1000
// s1bit = 0b00000000, // stop bits
s2bit = 0x04, // 0000 0100 1.5 for 5bit data; 2 otherwise
dlab = 0x80 // 1000 0000 divisor latch access bit
};
// Line Status Register
enum LineStatus {
DR = (1 << 0), // data ready: see if there is data to read
OE = (1 << 1), // overrun error: see if there has been data lost
PE = (1 << 2), // parity error: see if there was error in transmission
FE = (1 << 3), // framing error: see if a stop bit was missing
BI = (1 << 4), // break indicator: see if there is a break in data input
THRE = (1 << 5), // transmitter holding register empty: see if transmission buffer is empty
TEMT = (1 << 6), // transmitter empty: see if transmitter is not doing anything
ERRO = (1 << 7), // impending error: see if there is an error with a word in the input buffer
};
int
uart_thre(enum UART port)
{
return inb(port + LineStatus) & THRE;
}
void
uart_write(const FILE *self, char a)
{
while (uart_thre(self->id) == 0) {}
outb(a, self->id);
if (a == '\n') {
while (uart_thre(self->id) == 0) {}
outb('\r', self->id);
}
}
int
uart_puts(const FILE *self, const char *string, int length)
{
int written = 0;
if (length == -1)
while (*string != '\0') {
uart_write(self, *string);
++string;
++written;
}
else
for (int i = 0; i < length; ++i) {
uart_write(self, string[i]);
++written;
}
return written;
}
void
uart_flush(__attribute__((unused)) const FILE *self)
{
}
FILE uart_stream;
FILE *
uart_init(enum UART port)
{
outb(0x00, port + 1); // Disable all interrupts
outb(0x80, port + 3); // Enable DLAB (set baud rate divisor)
outb(0x03, port + 0); // Set divisor to 3 (lo byte) 38400 baud
outb(0x00, port + 1); // (hi byte)
outb(0x03, port + 3); // 8 bits, no parity, one stop bit
outb(0xc7, port + 2); // Enable FIFO, clear them, with 14-byte threshold
outb(0x0b, port + 4); // IRQs enabled, RTS/DSR set
outb(0x1e, port + 4); // Set in loopback mode, test the serial chip
outb(0xae, port + 0); // 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 + 0) != 0xae) { return NULL; }
// 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(0x0f, port + 4);
uart_stream.id = port;
uart_stream.putc = &uart_write;
uart_stream.puts = &uart_puts;
uart_stream.flush = &uart_flush;
return &uart_stream;
}
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