1 files changed, 78 insertions, 0 deletions
diff --git a/devices/uart/uart_16550.c b/devices/uart/uart_16550.c
new file mode 100644
index 0000000..4697cf3
--- /dev/null
+++ b/devices/uart/uart_16550.c
@@ -0,0 +1,78 @@
+#include "uart_16550.h"
+#include <stddef.h>
+
+int
+uart_thre(unsigned short port)
+{
+  return inb(port + LineStatus) & THRE;
+}
+
+void
+uart_putc(const FILE *self, char a)
+{
+  const unsigned short port = (unsigned short)self->id;
+
+  while (uart_thre(port) == 0) {}
+  outb((unsigned char)a, port);
+
+  if (a == '\n') {
+    while (uart_thre(port) == 0) {}
+    outb('\r', port);
+  }
+}
+
+int
+uart_puts(const FILE *self, const char *string, int length)
+{
+  int i;
+  int written = 0;
+
+  if (length == -1)
+    while (*string != '\0') {
+      uart_putc(self, *string);
+      ++string;
+      ++written;
+    }
+
+  else
+    for (i = 0; i < length; ++i) {
+      uart_putc(self, string[i]);
+      ++written;
+    }
+
+  return written;
+}
+
+void
+uart_flush(__attribute__((unused)) const FILE *self)
+{
+}
+
+FILE uart_stream;
+
+FILE *
+uart_init(unsigned short 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_putc;
+  uart_stream.puts = &uart_puts;
+  uart_stream.flush = &uart_flush;
+  return &uart_stream;
+}