Refactor the i8042 module to be thread-safe.

Any command/data coming from host will be placed in from_host queue, and
the interrupt handler returns immediately. The i8042_command_task() will
handle them later.

Data reply to the host will be protected by the mutex.

BUG=chrome-os-partner:10090
TEST=randomly play around on the link board.

Change-Id: Ic19d5abd1abf8dc261ddaad4224cd9305c2f36a4
Signed-off-by: Louis Yung-Chieh Lo <yjlou@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/24299
Commit-Ready: Yung-Chieh Lo <yjlou%chromium.org@gtempaccount.com>
Reviewed-by: Yung-Chieh Lo <yjlou%chromium.org@gtempaccount.com>
Tested-by: Yung-Chieh Lo <yjlou%chromium.org@gtempaccount.com>

include/queue.h

@@ -0,0 +1,40 @@
+/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ *
+ * Queue data structure.
+ */
+
+#include "common.h"
+
+/* Generic queue container.
+ *
+ *   head: next to dequeqe
+ *   tail: next to enqueue
+ *
+ *   Empty:
+ *     head == tail
+ *   Full:
+ *     ((tail + 1) % buf_bytes) == head
+ */
+struct queue {
+	int head, tail;
+	int buf_bytes;   /* size of buffer (in byte) */
+	int unit_bytes;  /* size of unit (in byte) */
+	uint8_t *buf;
+};
+
+/* Reset the queue to empty state. */
+void queue_reset(struct queue *queue);
+
+/* Return TRUE if the queue is empty. */
+int queue_is_empty(const struct queue *q);
+
+/* Return TRUE if the queue has at least one unit space. */
+int queue_has_space(const struct queue *q, int unit_count);
+
+/* Add multiple units into queue. */
+void queue_add_units(struct queue *q, const void *src, int unit_count);
+
+/* Remove one unit from the begin of the queue. */
+int queue_remove_unit(struct queue *q, void *dest);