technically speaking deadlock free, but starves

1 files changed, 55 insertions, 0 deletions

diff --git a/src/uart/simple_uart.c b/src/uart/simple_uart.c
new file mode 100644
index 0000000..e640ae1
--- /dev/null
+++ b/src/uart/simple_uart.c
@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include <gran/uart/simple_uart.h>
+
+struct simple_uart {
+	struct component component;
+
+	struct component *send;
+	struct packet pkt;
+	bool busy;
+};
+
+static stat simple_uart_clock(struct simple_uart *uart)
+{
+	if (!uart->busy)
+		return OK;
+
+	stat r = SEND(uart, uart->send, uart->pkt);
+	if (r == EBUSY)
+		return OK;
+
+	uart->busy = false;
+	return OK;
+}
+
+static stat simple_uart_receive(struct simple_uart *uart, struct component *from, struct packet pkt)
+{
+	if (uart->busy)
+		return EBUSY;
+
+	uart->busy = true;
+	uart->send = from;
+	uart->pkt = response(pkt);
+
+	size_t size = packet_convsize(&pkt);
+	if (size != 1) {
+		set_flags(&uart->pkt, PACKET_ERROR);
+		return OK;
+	}
+
+	putchar(packet_convu8(&pkt));
+	fflush(stdout);
+	set_flags(&uart->pkt, PACKET_DONE);
+	return OK;
+}
+
+struct component *create_simple_uart()
+{
+	struct simple_uart *uart = calloc(1, sizeof(struct simple_uart));
+	if (!uart)
+		return NULL;
+
+	uart->component.receive = (receive_callback)simple_uart_receive;
+	uart->component.clock = (clock_callback)simple_uart_clock;
+	return (struct component *)uart;
+}