Streams: Define a lower level abstraction for queue access

This adds a new pair of interfaces called producer and consumer
which are simpler (in that they don't hold onto the underlying
queue) than the stream interfaces.  This makes it easier to
share a single queue between the endpoints that will manipulate
it.  It was not possible to share a queue between two objects
that implemented the in_stream and out_stream interfaces.

This also adds a pair of adaptors that can convert a producer
or consumer into a stream of the correct type.  These adaptors
will be used for existing code once the usb-stream and usart
drivers are converted over to use the producer/consumer
interfaces instead of the stream interfaces.

Signed-off-by: Anton Staaf <robotboy@chromium.org>

BRANCH=None
BUG=None
TEST=make buildall -j

Change-Id: I42b4b1ac15cca28e1adc6d3cea315f15e17a0b4d
Reviewed-on: https://chromium-review.googlesource.com/250941
Trybot-Ready: Anton Staaf <robotboy@chromium.org>
Tested-by: Anton Staaf <robotboy@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Queue: Anton Staaf <robotboy@chromium.org>

3 files changed, 236 insertions, 0 deletions

diff --git a/include/consumer.h b/include/consumer.h
new file mode 100644
index 0000000000..4a456de512
--- /dev/null
+++ b/include/consumer.h
@@ -0,0 +1,81 @@
+/* Copyright (c) 2015 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.
+ *
+ * Consumer interface
+ *
+ * The consumer abstraction allows for code that wants to be able to read from
+ * a queue, and be notified of new additions to the queue, or of requests to
+ * flush (empty) the queue.
+ */
+#ifndef INCLUDE_CONSUMER_H
+#define INCLUDE_CONSUMER_H
+
+#include "queue.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+struct consumer;
+struct producer;
+
+struct consumer_ops {
+	/*
+	 * Inform the consumer that count units were written to the queue.
+	 * This gives it the oportunity to read additional units from the queue
+	 * or to wake up a task or interrupt to do the same.  If a consumer has
+	 * no need for this information it can set this to NULL.
+	 */
+	void (*written)(struct consumer const *consumer, size_t count);
+
+	/*
+	 * Flush (read) everything from the associated queue.  This call blocks
+	 * until the consumer has flushed the queue.
+	 */
+	void (*flush)(struct consumer const *consumer);
+};
+
+struct consumer {
+	/*
+	 * A consumer references the producer at the other end of the queue.
+	 * This allows the consumer to notify the producer when units are
+	 * removed from the queue.
+	 */
+	struct producer const *producer;
+
+	/*
+	 * A consumer also references the queue that it is reading from.  This
+	 * and the producer reference above could be more flexibly replaced by
+	 * a queue manager object that could handle multiple producer/consumers
+	 * or alternate notification mechanisms.  But that complexity is not
+	 * yet warranted.
+	 */
+	struct queue const *queue;
+
+	struct consumer_ops const *ops;
+};
+
+/*
+ * Notify the consumer by calling its written method directly, as opposed to
+ * from a deferred callback or another task.
+ */
+void consumer_notify_directly(struct consumer const *consumer, size_t count);
+
+/*
+ * Read a single unit from the queue and notify the associated producer.
+ * Return the number of units read.
+ */
+size_t consumer_read_unit(struct consumer const *consumer, void *unit);
+
+/*
+ * Read multiple units from the queue, using the provided memcpy like routine
+ * and notify the producer.  Return the number of units read.
+ */
+size_t consumer_read_memcpy(struct consumer const *consumer,
+			    void *units,
+			    size_t count,
+			    void *(*memcpy)(void *dest,
+					    void const *src,
+					    size_t n));
+
+#endif /* INCLUDE_CONSUMER_H */
diff --git a/include/producer.h b/include/producer.h
new file mode 100644
index 0000000000..d42e148ea6
--- /dev/null
+++ b/include/producer.h
@@ -0,0 +1,75 @@
+/* Copyright (c) 2015 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.
+ *
+ * Producer interface
+ *
+ * The producer abstraction allows for code that wants to write into a queue and
+ * be notified when the queue is read from so that it can take action, such as
+ * adding new units to the queue.
+ */
+#ifndef INCLUDE_PRODUCER_H
+#define INCLUDE_PRODUCER_H
+
+#include "queue.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+struct consumer;
+struct producer;
+
+struct producer_ops {
+	/*
+	 * Inform the producer that count units were read from the queue.  This
+	 * gives it the oportunity to write additional units to the queue or to
+	 * wake up a task or interrupt to do the same.  If a producer has no
+	 * need for this information it can set this to NULL.
+	 */
+	void (*read)(struct producer const *producer, size_t count);
+};
+
+struct producer {
+	/*
+	 * A producer references the consumer at the other end of the queue.
+	 * This allows the producer to notify the consumer when new units are
+	 * added to the queue.
+	 */
+	struct consumer const *consumer;
+
+	/*
+	 * A producer also references the queue that it is writing into.  This
+	 * and the consumer reference above could be more flexibly replaced by
+	 * a queue manager object that could handle multiple producer/consumers
+	 * or alternate notification mechanisms.  But that complexity is not
+	 * yet warranted.
+	 */
+	struct queue const *queue;
+
+	struct producer_ops const *ops;
+};
+
+/*
+ * Notify the producer by calling its read method directly, as opposed to from
+ * a deferred callback or another task.
+ */
+void producer_notify_directly(struct producer const *producer, size_t count);
+
+/*
+ * Write a single unit to the queue and notify the associated consumer.  Return
+ * the number of units written.
+ */
+size_t producer_write_unit(struct producer const *producer, void const *unit);
+
+/*
+ * Write multiple units to the queue, using the provided memcpy like routine
+ * and notify the consumer.  Return the number of units written.
+ */
+size_t producer_write_memcpy(struct producer const *producer,
+			     void const *units,
+			     size_t count,
+			     void *(*memcpy)(void *dest,
+					     void const *src,
+					     size_t n));
+
+#endif /* INCLUDE_PRODUCER_H */
diff --git a/include/stream_adaptor.h b/include/stream_adaptor.h
new file mode 100644
index 0000000000..916ab6e78d
--- /dev/null
+++ b/include/stream_adaptor.h
@@ -0,0 +1,80 @@
+/* Copyright (c) 2015 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.
+ */
+#ifndef INCLUDE_STREAM_ADAPTOR_H
+#define INCLUDE_STREAM_ADAPTOR_H
+
+/* STM32 USART driver for Chrome EC */
+
+#include "common.h"
+#include "in_stream.h"
+#include "out_stream.h"
+#include "consumer.h"
+#include "producer.h"
+
+/*
+ * +..........+               +..........+------+...........+
+ * .          .<------------->.          |      |           .
+ * . Producer .  +---------+  . Consumer | ISFP | In Stream .
+ * .          .->|  Queue  |->.          |      |           .
+ * +..........+  +---------+  +..........+------+...........+
+ */
+
+struct in_stream_from_producer {
+	struct consumer consumer;
+	struct in_stream in;
+};
+
+/*
+ *
+ */
+extern struct in_stream_ops const in_stream_from_producer_in_stream_ops;
+extern struct consumer_ops const in_stream_from_producer_consumer_ops;
+
+#define IN_STREAM_FROM_PRODUCER(NAME, PRODUCER, QUEUE, READY)		\
+	struct in_stream_from_producer const NAME = {			\
+		.consumer = {						\
+			.producer = &PRODUCER,				\
+			.queue    = &QUEUE,				\
+			.ops      = &in_stream_from_producer_consumer_ops, \
+		},							\
+		.in = {							\
+			.ready = READY,					\
+			.ops   = &in_stream_from_producer_in_stream_ops, \
+		},							\
+	};
+
+/*
+ * +..........+               +..........+------+............+
+ * .          .<------------->.          |      |            .
+ * . Consumer .  +---------+  . Producer | OSFC | Out Stream .
+ * .          .<-|  Queue  |<-.          |      |            .
+ * +..........+  +---------+  +..........+------+............+
+ */
+
+struct out_stream_from_consumer {
+	struct producer producer;
+	struct out_stream out;
+};
+
+/*
+ *
+ */
+extern struct out_stream_ops const out_stream_from_consumer_out_stream_ops;
+extern struct producer_ops const out_stream_from_consumer_producer_ops;
+
+#define OUT_STREAM_FROM_CONSUMER(NAME, CONSUMER, QUEUE, READY)		\
+	struct out_stream_from_consumer const NAME = {			\
+		.producer = {						\
+			.consumer = &CONSUMER,				\
+			.queue    = &QUEUE,				\
+			.ops      = &out_stream_from_consumer_producer_ops, \
+		},							\
+		.out = {						\
+			.ready = READY,					\
+			.ops   = &out_stream_from_consumer_out_stream_ops, \
+		},							\
+	};
+
+#endif /* INCLUDE_STREAM_ADAPTOR_H */