1 files changed, 110 insertions, 0 deletions
diff --git a/devices/uart_16550.cpp b/devices/uart_16550.cpp
new file mode 100644
index 0000000..9620981
--- /dev/null
+++ b/devices/uart_16550.cpp
@@ -0,0 +1,110 @@
+#include "uart.hpp"
+#include <sys/io.hpp>
+
+template <UART port> struct Uart16550 : public kIoDevice, private Port<unsigned short, port> {
+  using Base = Port<unsigned short, port>;
+  using Ports = UART;
+  using PortOffset = UARTPortOffset;
+
+  // Line Control
+  // | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
+  // |dla|   | parity    | s | data  |
+  enum LineControl : unsigned char {
+    d5bit = 0x00, // 0000 0000  data bits
+    d6bit = 0x01, // 0000 0001
+    d7bit = 0x02, // 0000 0010
+    d8bit = 0x03, // 0000 0011
+    none = 0x00,  // 0000 0000  parity bits
+    odd = 0x08,   // 0000 1000
+    even = 0x18,  // 0001 1000
+    mark = 0x28,  // 0010 1000
+    space = 0x38, // 0011 1000
+    s1bit = 0x00, // 0000 0000  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 : unsigned char {
+    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
+  };
+
+  [[nodiscard]] static bool
+  test()
+  {
+    Base::out(0x00, 1); // Disable all interrupts
+    Base::out(0x80, 3); // Enable DLAB (set baud rate divisor)
+    Base::out(0x03, 0); // Set divisor to 3 (lo byte) 38400 baud
+    Base::out(0x00, 1); //                  (hi byte)
+    Base::out(0x03, 3); // 8 bits, no parity, one stop bit
+    Base::out(0xc7, 2); // Enable FIFO, clear them, with 14-byte threshold
+    Base::out(0x0b, 4); // IRQs enabled, RTS/DSR set
+    Base::out(0x1e, 4); // Set in loopback mode, test the serial chip
+    Base::out(0xae, 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 (Base::in() != 0xae) { 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)
+    Base::out(0x0f, 4);
+    return true;
+  }
+
+  [[nodiscard]] static bool
+  thre()
+  {
+    return Base::in(PortOffset::LineStatus)&THRE;
+  }
+
+  void
+  putc(char a) override
+  {
+    while (!thre()) {}
+    Base::out(a);
+    if (a == '\n') putc('\r');
+  }
+
+  int
+  puts(const char *string, int length) override
+  {
+    int written = 0;
+
+    if (length == -1)
+      while (*string != '\0') {
+        putc(*string);
+        ++string;
+        ++written;
+      }
+
+    else {
+      for (int i = 0; i < length; ++i) putc(string[i]);
+      written += length;
+    }
+
+    return written;
+  }
+
+  void
+  flush() override
+  {
+  }
+};
+
+static_assert(sizeof(Uart16550<COM1>) == sizeof(void *));
+
+template <>
+FILE *
+uart_init<COM1>()
+{
+  static Uart16550<COM1> device;
+  return &device;
+}