kernel: add equeue object

equeue is a way for the kernel to deliver events to userspace programs.

include/kernel/equeue.h

@@ -0,0 +1,34 @@
+#ifndef KERNEL_EQUEUE_H_
+#define KERNEL_EQUEUE_H_
+
+#include <kernel/locks.h>
+#include <kernel/object.h>
+#include <kernel/sched.h>
+#include <mango/types.h>
+
+#define EQUEUE_PACKET_MAX 100
+
+enum equeue_flags {
+	EQUEUE_WAIT,
+	EQUEUE_DISCARD,
+};
+
+struct equeue {
+	struct object eq_base;
+	unsigned short eq_read_ptr, eq_write_ptr;
+	equeue_packet_t eq_packets[EQUEUE_PACKET_MAX];
+	struct waitqueue eq_wq;
+};
+
+extern kern_status_t equeue_type_init(void);
+extern struct equeue *equeue_cast(struct object *obj);
+
+extern struct equeue *equeue_create(void);
+
+extern kern_status_t equeue_enqueue(
+	struct equeue *q,
+	const equeue_packet_t *pkt,
+	enum equeue_flags flags);
+extern kern_status_t equeue_dequeue(struct equeue *q, equeue_packet_t *out);
+
+#endif