technically speaking deadlock free, but starves

1 files changed, 117 insertions, 0 deletions

diff --git a/src/bus/simple_bus.c b/src/bus/simple_bus.c
new file mode 100644
index 0000000..1932419
--- /dev/null
+++ b/src/bus/simple_bus.c
@@ -0,0 +1,117 @@
+/* SPDX-License-Identifier: copyleft-next-0.3.1 */
+/* Copyright 2023 Kim Kuparinen < kimi.h.kuparinen@gmail.com > */
+#include <stdbool.h>
+
+#include <gran/bus/simple_bus.h>
+#include <gran/vec.h>
+
+struct bus_region {
+	uint64_t addr;
+	uint64_t size;
+	struct component *component;
+};
+
+struct simple_bus {
+	struct component component;
+	struct vec regions;
+
+	struct component *send;
+	struct packet pkt;
+	bool busy;
+};
+
+static struct bus_region *find_bus_region(struct simple_bus *bus, uint64_t addr)
+{
+	foreach_vec(i, bus->regions) {
+		struct bus_region *r = vec_at(&bus->regions, i);
+		if (addr >= r->addr && addr < (r->addr + r->size))
+			return r;
+	}
+
+	return NULL;
+}
+
+static stat simple_bus_clock(struct simple_bus *bus)
+{
+	if (bus->busy) {
+		stat r = SEND(bus, bus->send, bus->pkt);
+		if (r == EBUSY)
+			return OK;
+
+		bus->busy = false;
+		return r;
+	}
+
+	return OK;
+}
+
+static stat simple_bus_receive(struct simple_bus *bus, struct component *from, struct packet pkt)
+{
+	if (bus->busy)
+		return EBUSY;
+
+	bus->busy = true;
+
+	struct bus_region *region = find_bus_region(bus, pkt.to);
+	if (!region) {
+		warn("illegal address on bus %s at %" PRIuPTR,
+		     bus->component.name, pkt.to);
+
+		bus->send = from;
+		bus->pkt = response(pkt);
+		set_flags(&bus->pkt, PACKET_ERROR);
+		return OK;
+	}
+
+	bus->send = region->component;
+	bus->pkt = pkt;
+	return OK;
+}
+
+static void simple_bus_destroy(struct simple_bus *bus)
+{
+	vec_destroy(&bus->regions);
+	free(bus);
+}
+
+struct component *create_simple_bus()
+{
+	struct simple_bus *bus = calloc(1, sizeof(struct simple_bus));
+	if (!bus)
+		return NULL;
+
+	bus->component.receive = (receive_callback)simple_bus_receive;
+	bus->component.clock = (clock_callback)simple_bus_clock;
+
+	bus->component.destroy = (destroy_callback)simple_bus_destroy;
+	bus->regions = vec_create(sizeof(struct bus_region));
+
+	return (struct component *)bus;
+}
+
+stat simple_bus_add(struct component *bus, struct component *component,
+                    uint64_t addr, uint64_t size)
+{
+	struct simple_bus *b = (struct simple_bus *)bus;
+	struct bus_region *found = find_bus_region(b, addr);
+	if (!found)        found = find_bus_region(b, addr + size);
+
+	if (found) {
+		error("%s overlaps with %s at %" PRIuPTR,
+		      found->component->name,
+		      component->name,
+		      found->addr
+		      );
+
+		return EEXISTS;
+	}
+
+	struct bus_region new = (struct bus_region){
+		.component = component,
+		.addr = addr,
+		.size = size
+	};
+
+	vect_append(struct bus_region, b->regions, &new);
+	return OK;
+}