[patch 03/32] greybus: operations logic

[Greg KH <gregkh@linuxfoundation.org>]

This is the Greybus operations code, handling the logic for them.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/greybus/operation.c | 1239 ++++++++++++++++++++++++++++++++++++++++++++
 drivers/greybus/operation.h |  210 +++++++
 2 files changed, 1449 insertions(+)

--- /dev/null
+++ b/drivers/greybus/operation.c
@@ -0,0 +1,1239 @@
+/*
+ * Greybus operations
+ *
+ * Copyright 2014-2015 Google Inc.
+ * Copyright 2014-2015 Linaro Ltd.
+ *
+ * Released under the GPLv2 only.
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/workqueue.h>
+
+#include "greybus.h"
+#include "greybus_trace.h"
+
+static struct kmem_cache *gb_operation_cache;
+static struct kmem_cache *gb_message_cache;
+
+/* Workqueue to handle Greybus operation completions. */
+static struct workqueue_struct *gb_operation_completion_wq;
+
+/* Wait queue for synchronous cancellations. */
+static DECLARE_WAIT_QUEUE_HEAD(gb_operation_cancellation_queue);
+
+/*
+ * Protects updates to operation->errno.
+ */
+static DEFINE_SPINLOCK(gb_operations_lock);
+
+static int gb_operation_response_send(struct gb_operation *operation,
+					int errno);
+
+/*
+ * Increment operation active count and add to connection list unless the
+ * connection is going away.
+ *
+ * Caller holds operation reference.
+ */
+static int gb_operation_get_active(struct gb_operation *operation)
+{
+	struct gb_connection *connection = operation->connection;
+	unsigned long flags;
+
+	spin_lock_irqsave(&connection->lock, flags);
+	switch (connection->state) {
+	case GB_CONNECTION_STATE_ENABLED:
+		break;
+	case GB_CONNECTION_STATE_ENABLED_TX:
+		if (gb_operation_is_incoming(operation))
+			goto err_unlock;
+		break;
+	case GB_CONNECTION_STATE_DISCONNECTING:
+		if (!gb_operation_is_core(operation))
+			goto err_unlock;
+		break;
+	default:
+		goto err_unlock;
+	}
+
+	if (operation->active++ == 0)
+		list_add_tail(&operation->links, &connection->operations);
+
+	trace_gb_operation_get_active(operation);
+
+	spin_unlock_irqrestore(&connection->lock, flags);
+
+	return 0;
+
+err_unlock:
+	spin_unlock_irqrestore(&connection->lock, flags);
+
+	return -ENOTCONN;
+}
+
+/* Caller holds operation reference. */
+static void gb_operation_put_active(struct gb_operation *operation)
+{
+	struct gb_connection *connection = operation->connection;
+	unsigned long flags;
+
+	spin_lock_irqsave(&connection->lock, flags);
+
+	trace_gb_operation_put_active(operation);
+
+	if (--operation->active == 0) {
+		list_del(&operation->links);
+		if (atomic_read(&operation->waiters))
+			wake_up(&gb_operation_cancellation_queue);
+	}
+	spin_unlock_irqrestore(&connection->lock, flags);
+}
+
+static bool gb_operation_is_active(struct gb_operation *operation)
+{
+	struct gb_connection *connection = operation->connection;
+	unsigned long flags;
+	bool ret;
+
+	spin_lock_irqsave(&connection->lock, flags);
+	ret = operation->active;
+	spin_unlock_irqrestore(&connection->lock, flags);
+
+	return ret;
+}
+
+/*
+ * Set an operation's result.
+ *
+ * Initially an outgoing operation's errno value is -EBADR.
+ * If no error occurs before sending the request message the only
+ * valid value operation->errno can be set to is -EINPROGRESS,
+ * indicating the request has been (or rather is about to be) sent.
+ * At that point nobody should be looking at the result until the
+ * response arrives.
+ *
+ * The first time the result gets set after the request has been
+ * sent, that result "sticks."  That is, if two concurrent threads
+ * race to set the result, the first one wins.  The return value
+ * tells the caller whether its result was recorded; if not the
+ * caller has nothing more to do.
+ *
+ * The result value -EILSEQ is reserved to signal an implementation
+ * error; if it's ever observed, the code performing the request has
+ * done something fundamentally wrong.  It is an error to try to set
+ * the result to -EBADR, and attempts to do so result in a warning,
+ * and -EILSEQ is used instead.  Similarly, the only valid result
+ * value to set for an operation in initial state is -EINPROGRESS.
+ * Attempts to do otherwise will also record a (successful) -EILSEQ
+ * operation result.
+ */
+static bool gb_operation_result_set(struct gb_operation *operation, int result)
+{
+	unsigned long flags;
+	int prev;
+
+	if (result == -EINPROGRESS) {
+		/*
+		 * -EINPROGRESS is used to indicate the request is
+		 * in flight.  It should be the first result value
+		 * set after the initial -EBADR.  Issue a warning
+		 * and record an implementation error if it's
+		 * set at any other time.
+		 */
+		spin_lock_irqsave(&gb_operations_lock, flags);
+		prev = operation->errno;
+		if (prev == -EBADR)
+			operation->errno = result;
+		else
+			operation->errno = -EILSEQ;
+		spin_unlock_irqrestore(&gb_operations_lock, flags);
+		WARN_ON(prev != -EBADR);
+
+		return true;
+	}
+
+	/*
+	 * The first result value set after a request has been sent
+	 * will be the final result of the operation.  Subsequent
+	 * attempts to set the result are ignored.
+	 *
+	 * Note that -EBADR is a reserved "initial state" result
+	 * value.  Attempts to set this value result in a warning,
+	 * and the result code is set to -EILSEQ instead.
+	 */
+	if (WARN_ON(result == -EBADR))
+		result = -EILSEQ; /* Nobody should be setting -EBADR */
+
+	spin_lock_irqsave(&gb_operations_lock, flags);
+	prev = operation->errno;
+	if (prev == -EINPROGRESS)
+		operation->errno = result;	/* First and final result */
+	spin_unlock_irqrestore(&gb_operations_lock, flags);
+
+	return prev == -EINPROGRESS;
+}
+
+int gb_operation_result(struct gb_operation *operation)
+{
+	int result = operation->errno;
+
+	WARN_ON(result == -EBADR);
+	WARN_ON(result == -EINPROGRESS);
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(gb_operation_result);
+
+/*
+ * Looks up an outgoing operation on a connection and returns a refcounted
+ * pointer if found, or NULL otherwise.
+ */
+static struct gb_operation *
+gb_operation_find_outgoing(struct gb_connection *connection, u16 operation_id)
+{
+	struct gb_operation *operation;
+	unsigned long flags;
+	bool found = false;
+
+	spin_lock_irqsave(&connection->lock, flags);
+	list_for_each_entry(operation, &connection->operations, links)
+		if (operation->id == operation_id &&
+				!gb_operation_is_incoming(operation)) {
+			gb_operation_get(operation);
+			found = true;
+			break;
+		}
+	spin_unlock_irqrestore(&connection->lock, flags);
+
+	return found ? operation : NULL;
+}
+
+static int gb_message_send(struct gb_message *message, gfp_t gfp)
+{
+	struct gb_connection *connection = message->operation->connection;
+
+	trace_gb_message_send(message);
+	return connection->hd->driver->message_send(connection->hd,
+					connection->hd_cport_id,
+					message,
+					gfp);
+}
+
+/*
+ * Cancel a message we have passed to the host device layer to be sent.
+ */
+static void gb_message_cancel(struct gb_message *message)
+{
+	struct gb_host_device *hd = message->operation->connection->hd;
+
+	hd->driver->message_cancel(message);
+}
+
+static void gb_operation_request_handle(struct gb_operation *operation)
+{
+	struct gb_connection *connection = operation->connection;
+	int status;
+	int ret;
+
+	if (connection->handler) {
+		status = connection->handler(operation);
+	} else {
+		dev_err(&connection->hd->dev,
+			"%s: unexpected incoming request of type 0x%02x\n",
+			connection->name, operation->type);
+
+		status = -EPROTONOSUPPORT;
+	}
+
+	ret = gb_operation_response_send(operation, status);
+	if (ret) {
+		dev_err(&connection->hd->dev,
+			"%s: failed to send response %d for type 0x%02x: %d\n",
+			connection->name, status, operation->type, ret);
+		return;
+	}
+}
+
+/*
+ * Process operation work.
+ *
+ * For incoming requests, call the protocol request handler. The operation
+ * result should be -EINPROGRESS at this point.
+ *
+ * For outgoing requests, the operation result value should have
+ * been set before queueing this.  The operation callback function
+ * allows the original requester to know the request has completed
+ * and its result is available.
+ */
+static void gb_operation_work(struct work_struct *work)
+{
+	struct gb_operation *operation;
+
+	operation = container_of(work, struct gb_operation, work);
+
+	if (gb_operation_is_incoming(operation))
+		gb_operation_request_handle(operation);
+	else
+		operation->callback(operation);
+
+	gb_operation_put_active(operation);
+	gb_operation_put(operation);
+}
+
+static void gb_operation_message_init(struct gb_host_device *hd,
+				struct gb_message *message, u16 operation_id,
+				size_t payload_size, u8 type)
+{
+	struct gb_operation_msg_hdr *header;
+
+	header = message->buffer;
+
+	message->header = header;
+	message->payload = payload_size ? header + 1 : NULL;
+	message->payload_size = payload_size;
+
+	/*
+	 * The type supplied for incoming message buffers will be
+	 * GB_REQUEST_TYPE_INVALID. Such buffers will be overwritten by
+	 * arriving data so there's no need to initialize the message header.
+	 */
+	if (type != GB_REQUEST_TYPE_INVALID) {
+		u16 message_size = (u16)(sizeof(*header) + payload_size);
+
+		/*
+		 * For a request, the operation id gets filled in
+		 * when the message is sent.  For a response, it
+		 * will be copied from the request by the caller.
+		 *
+		 * The result field in a request message must be
+		 * zero.  It will be set just prior to sending for
+		 * a response.
+		 */
+		header->size = cpu_to_le16(message_size);
+		header->operation_id = 0;
+		header->type = type;
+		header->result = 0;
+	}
+}
+
+/*
+ * Allocate a message to be used for an operation request or response.
+ * Both types of message contain a common header.  The request message
+ * for an outgoing operation is outbound, as is the response message
+ * for an incoming operation.  The message header for an outbound
+ * message is partially initialized here.
+ *
+ * The headers for inbound messages don't need to be initialized;
+ * they'll be filled in by arriving data.
+ *
+ * Our message buffers have the following layout:
+ *	message header  \_ these combined are
+ *	message payload /  the message size
+ */
+static struct gb_message *
+gb_operation_message_alloc(struct gb_host_device *hd, u8 type,
+				size_t payload_size, gfp_t gfp_flags)
+{
+	struct gb_message *message;
+	struct gb_operation_msg_hdr *header;
+	size_t message_size = payload_size + sizeof(*header);
+
+	if (message_size > hd->buffer_size_max) {
+		dev_warn(&hd->dev, "requested message size too big (%zu > %zu)\n",
+				message_size, hd->buffer_size_max);
+		return NULL;
+	}
+
+	/* Allocate the message structure and buffer. */
+	message = kmem_cache_zalloc(gb_message_cache, gfp_flags);
+	if (!message)
+		return NULL;
+
+	message->buffer = kzalloc(message_size, gfp_flags);
+	if (!message->buffer)
+		goto err_free_message;
+
+	/* Initialize the message.  Operation id is filled in later. */
+	gb_operation_message_init(hd, message, 0, payload_size, type);
+
+	return message;
+
+err_free_message:
+	kmem_cache_free(gb_message_cache, message);
+
+	return NULL;
+}
+
+static void gb_operation_message_free(struct gb_message *message)
+{
+	kfree(message->buffer);
+	kmem_cache_free(gb_message_cache, message);
+}
+
+/*
+ * Map an enum gb_operation_status value (which is represented in a
+ * message as a single byte) to an appropriate Linux negative errno.
+ */
+static int gb_operation_status_map(u8 status)
+{
+	switch (status) {
+	case GB_OP_SUCCESS:
+		return 0;
+	case GB_OP_INTERRUPTED:
+		return -EINTR;
+	case GB_OP_TIMEOUT:
+		return -ETIMEDOUT;
+	case GB_OP_NO_MEMORY:
+		return -ENOMEM;
+	case GB_OP_PROTOCOL_BAD:
+		return -EPROTONOSUPPORT;
+	case GB_OP_OVERFLOW:
+		return -EMSGSIZE;
+	case GB_OP_INVALID:
+		return -EINVAL;
+	case GB_OP_RETRY:
+		return -EAGAIN;
+	case GB_OP_NONEXISTENT:
+		return -ENODEV;
+	case GB_OP_MALFUNCTION:
+		return -EILSEQ;
+	case GB_OP_UNKNOWN_ERROR:
+	default:
+		return -EIO;
+	}
+}
+
+/*
+ * Map a Linux errno value (from operation->errno) into the value
+ * that should represent it in a response message status sent
+ * over the wire.  Returns an enum gb_operation_status value (which
+ * is represented in a message as a single byte).
+ */
+static u8 gb_operation_errno_map(int errno)
+{
+	switch (errno) {
+	case 0:
+		return GB_OP_SUCCESS;
+	case -EINTR:
+		return GB_OP_INTERRUPTED;
+	case -ETIMEDOUT:
+		return GB_OP_TIMEOUT;
+	case -ENOMEM:
+		return GB_OP_NO_MEMORY;
+	case -EPROTONOSUPPORT:
+		return GB_OP_PROTOCOL_BAD;
+	case -EMSGSIZE:
+		return GB_OP_OVERFLOW;	/* Could be underflow too */
+	case -EINVAL:
+		return GB_OP_INVALID;
+	case -EAGAIN:
+		return GB_OP_RETRY;
+	case -EILSEQ:
+		return GB_OP_MALFUNCTION;
+	case -ENODEV:
+		return GB_OP_NONEXISTENT;
+	case -EIO:
+	default:
+		return GB_OP_UNKNOWN_ERROR;
+	}
+}
+
+bool gb_operation_response_alloc(struct gb_operation *operation,
+					size_t response_size, gfp_t gfp)
+{
+	struct gb_host_device *hd = operation->connection->hd;
+	struct gb_operation_msg_hdr *request_header;
+	struct gb_message *response;
+	u8 type;
+
+	type = operation->type | GB_MESSAGE_TYPE_RESPONSE;
+	response = gb_operation_message_alloc(hd, type, response_size, gfp);
+	if (!response)
+		return false;
+	response->operation = operation;
+
+	/*
+	 * Size and type get initialized when the message is
+	 * allocated.  The errno will be set before sending.  All
+	 * that's left is the operation id, which we copy from the
+	 * request message header (as-is, in little-endian order).
+	 */
+	request_header = operation->request->header;
+	response->header->operation_id = request_header->operation_id;
+	operation->response = response;
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(gb_operation_response_alloc);
+
+/*
+ * Create a Greybus operation to be sent over the given connection.
+ * The request buffer will be big enough for a payload of the given
+ * size.
+ *
+ * For outgoing requests, the request message's header will be
+ * initialized with the type of the request and the message size.
+ * Outgoing operations must also specify the response buffer size,
+ * which must be sufficient to hold all expected response data.  The
+ * response message header will eventually be overwritten, so there's
+ * no need to initialize it here.
+ *
+ * Request messages for incoming operations can arrive in interrupt
+ * context, so they must be allocated with GFP_ATOMIC.  In this case
+ * the request buffer will be immediately overwritten, so there is
+ * no need to initialize the message header.  Responsibility for
+ * allocating a response buffer lies with the incoming request
+ * handler for a protocol.  So we don't allocate that here.
+ *
+ * Returns a pointer to the new operation or a null pointer if an
+ * error occurs.
+ */
+static struct gb_operation *
+gb_operation_create_common(struct gb_connection *connection, u8 type,
+				size_t request_size, size_t response_size,
+				unsigned long op_flags, gfp_t gfp_flags)
+{
+	struct gb_host_device *hd = connection->hd;
+	struct gb_operation *operation;
+
+	operation = kmem_cache_zalloc(gb_operation_cache, gfp_flags);
+	if (!operation)
+		return NULL;
+	operation->connection = connection;
+
+	operation->request = gb_operation_message_alloc(hd, type, request_size,
+							gfp_flags);
+	if (!operation->request)
+		goto err_cache;
+	operation->request->operation = operation;
+
+	/* Allocate the response buffer for outgoing operations */
+	if (!(op_flags & GB_OPERATION_FLAG_INCOMING)) {
+		if (!gb_operation_response_alloc(operation, response_size,
+						 gfp_flags)) {
+			goto err_request;
+		}
+	}
+
+	operation->flags = op_flags;
+	operation->type = type;
+	operation->errno = -EBADR;  /* Initial value--means "never set" */
+
+	INIT_WORK(&operation->work, gb_operation_work);
+	init_completion(&operation->completion);
+	kref_init(&operation->kref);
+	atomic_set(&operation->waiters, 0);
+
+	return operation;
+
+err_request:
+	gb_operation_message_free(operation->request);
+err_cache:
+	kmem_cache_free(gb_operation_cache, operation);
+
+	return NULL;
+}
+
+/*
+ * Create a new operation associated with the given connection.  The
+ * request and response sizes provided are the number of bytes
+ * required to hold the request/response payload only.  Both of
+ * these are allowed to be 0.  Note that 0x00 is reserved as an
+ * invalid operation type for all protocols, and this is enforced
+ * here.
+ */
+struct gb_operation *
+gb_operation_create_flags(struct gb_connection *connection,
+				u8 type, size_t request_size,
+				size_t response_size, unsigned long flags,
+				gfp_t gfp)
+{
+	struct gb_operation *operation;
+
+	if (WARN_ON_ONCE(type == GB_REQUEST_TYPE_INVALID))
+		return NULL;
+	if (WARN_ON_ONCE(type & GB_MESSAGE_TYPE_RESPONSE))
+		type &= ~GB_MESSAGE_TYPE_RESPONSE;
+
+	if (WARN_ON_ONCE(flags & ~GB_OPERATION_FLAG_USER_MASK))
+		flags &= GB_OPERATION_FLAG_USER_MASK;
+
+	operation = gb_operation_create_common(connection, type,
+						request_size, response_size,
+						flags, gfp);
+	if (operation)
+		trace_gb_operation_create(operation);
+
+	return operation;
+}
+EXPORT_SYMBOL_GPL(gb_operation_create_flags);
+
+struct gb_operation *
+gb_operation_create_core(struct gb_connection *connection,
+				u8 type, size_t request_size,
+				size_t response_size, unsigned long flags,
+				gfp_t gfp)
+{
+	struct gb_operation *operation;
+
+	flags |= GB_OPERATION_FLAG_CORE;
+
+	operation = gb_operation_create_common(connection, type,
+						request_size, response_size,
+						flags, gfp);
+	if (operation)
+		trace_gb_operation_create_core(operation);
+
+	return operation;
+}
+/* Do not export this function. */
+
+size_t gb_operation_get_payload_size_max(struct gb_connection *connection)
+{
+	struct gb_host_device *hd = connection->hd;
+
+	return hd->buffer_size_max - sizeof(struct gb_operation_msg_hdr);
+}
+EXPORT_SYMBOL_GPL(gb_operation_get_payload_size_max);
+
+static struct gb_operation *
+gb_operation_create_incoming(struct gb_connection *connection, u16 id,
+				u8 type, void *data, size_t size)
+{
+	struct gb_operation *operation;
+	size_t request_size;
+	unsigned long flags = GB_OPERATION_FLAG_INCOMING;
+
+	/* Caller has made sure we at least have a message header. */
+	request_size = size - sizeof(struct gb_operation_msg_hdr);
+
+	if (!id)
+		flags |= GB_OPERATION_FLAG_UNIDIRECTIONAL;
+
+	operation = gb_operation_create_common(connection, type,
+						request_size,
+						GB_REQUEST_TYPE_INVALID,
+						flags, GFP_ATOMIC);
+	if (!operation)
+		return NULL;
+
+	operation->id = id;
+	memcpy(operation->request->header, data, size);
+	trace_gb_operation_create_incoming(operation);
+
+	return operation;
+}
+
+/*
+ * Get an additional reference on an operation.
+ */
+void gb_operation_get(struct gb_operation *operation)
+{
+	kref_get(&operation->kref);
+}
+EXPORT_SYMBOL_GPL(gb_operation_get);
+
+/*
+ * Destroy a previously created operation.
+ */
+static void _gb_operation_destroy(struct kref *kref)
+{
+	struct gb_operation *operation;
+
+	operation = container_of(kref, struct gb_operation, kref);
+
+	trace_gb_operation_destroy(operation);
+
+	if (operation->response)
+		gb_operation_message_free(operation->response);
+	gb_operation_message_free(operation->request);
+
+	kmem_cache_free(gb_operation_cache, operation);
+}
+
+/*
+ * Drop a reference on an operation, and destroy it when the last
+ * one is gone.
+ */
+void gb_operation_put(struct gb_operation *operation)
+{
+	if (WARN_ON(!operation))
+		return;
+
+	kref_put(&operation->kref, _gb_operation_destroy);
+}
+EXPORT_SYMBOL_GPL(gb_operation_put);
+
+/* Tell the requester we're done */
+static void gb_operation_sync_callback(struct gb_operation *operation)
+{
+	complete(&operation->completion);
+}
+
+/**
+ * gb_operation_request_send() - send an operation request message
+ * @operation:	the operation to initiate
+ * @callback:	the operation completion callback
+ * @gfp:	the memory flags to use for any allocations
+ *
+ * The caller has filled in any payload so the request message is ready to go.
+ * The callback function supplied will be called when the response message has
+ * arrived, a unidirectional request has been sent, or the operation is
+ * cancelled, indicating that the operation is complete. The callback function
+ * can fetch the result of the operation using gb_operation_result() if
+ * desired.
+ *
+ * Return: 0 if the request was successfully queued in the host-driver queues,
+ * or a negative errno.
+ */
+int gb_operation_request_send(struct gb_operation *operation,
+				gb_operation_callback callback,
+				gfp_t gfp)
+{
+	struct gb_connection *connection = operation->connection;
+	struct gb_operation_msg_hdr *header;
+	unsigned int cycle;
+	int ret;
+
+	if (gb_connection_is_offloaded(connection))
+		return -EBUSY;
+
+	if (!callback)
+		return -EINVAL;
+
+	/*
+	 * Record the callback function, which is executed in
+	 * non-atomic (workqueue) context when the final result
+	 * of an operation has been set.
+	 */
+	operation->callback = callback;
+
+	/*
+	 * Assign the operation's id, and store it in the request header.
+	 * Zero is a reserved operation id for unidirectional operations.
+	 */
+	if (gb_operation_is_unidirectional(operation)) {
+		operation->id = 0;
+	} else {
+		cycle = (unsigned int)atomic_inc_return(&connection->op_cycle);
+		operation->id = (u16)(cycle % U16_MAX + 1);
+	}
+
+	header = operation->request->header;
+	header->operation_id = cpu_to_le16(operation->id);
+
+	gb_operation_result_set(operation, -EINPROGRESS);
+
+	/*
+	 * Get an extra reference on the operation. It'll be dropped when the
+	 * operation completes.
+	 */
+	gb_operation_get(operation);
+	ret = gb_operation_get_active(operation);
+	if (ret)
+		goto err_put;
+
+	ret = gb_message_send(operation->request, gfp);
+	if (ret)
+		goto err_put_active;
+
+	return 0;
+
+err_put_active:
+	gb_operation_put_active(operation);
+err_put:
+	gb_operation_put(operation);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gb_operation_request_send);
+
+/*
+ * Send a synchronous operation.  This function is expected to
+ * block, returning only when the response has arrived, (or when an
+ * error is detected.  The return value is the result of the
+ * operation.
+ */
+int gb_operation_request_send_sync_timeout(struct gb_operation *operation,
+						unsigned int timeout)
+{
+	int ret;
+	unsigned long timeout_jiffies;
+
+	ret = gb_operation_request_send(operation, gb_operation_sync_callback,
+					GFP_KERNEL);
+	if (ret)
+		return ret;
+
+	if (timeout)
+		timeout_jiffies = msecs_to_jiffies(timeout);
+	else
+		timeout_jiffies = MAX_SCHEDULE_TIMEOUT;
+
+	ret = wait_for_completion_interruptible_timeout(&operation->completion,
+							timeout_jiffies);
+	if (ret < 0) {
+		/* Cancel the operation if interrupted */
+		gb_operation_cancel(operation, -ECANCELED);
+	} else if (ret == 0) {
+		/* Cancel the operation if op timed out */
+		gb_operation_cancel(operation, -ETIMEDOUT);
+	}
+
+	return gb_operation_result(operation);
+}
+EXPORT_SYMBOL_GPL(gb_operation_request_send_sync_timeout);
+
+/*
+ * Send a response for an incoming operation request.  A non-zero
+ * errno indicates a failed operation.
+ *
+ * If there is any response payload, the incoming request handler is
+ * responsible for allocating the response message.  Otherwise the
+ * it can simply supply the result errno; this function will
+ * allocate the response message if necessary.
+ */
+static int gb_operation_response_send(struct gb_operation *operation,
+					int errno)
+{
+	struct gb_connection *connection = operation->connection;
+	int ret;
+
+	if (!operation->response &&
+			!gb_operation_is_unidirectional(operation)) {
+		if (!gb_operation_response_alloc(operation, 0, GFP_KERNEL))
+			return -ENOMEM;
+	}
+
+	/* Record the result */
+	if (!gb_operation_result_set(operation, errno)) {
+		dev_err(&connection->hd->dev, "request result already set\n");
+		return -EIO;	/* Shouldn't happen */
+	}
+
+	/* Sender of request does not care about response. */
+	if (gb_operation_is_unidirectional(operation))
+		return 0;
+
+	/* Reference will be dropped when message has been sent. */
+	gb_operation_get(operation);
+	ret = gb_operation_get_active(operation);
+	if (ret)
+		goto err_put;
+
+	/* Fill in the response header and send it */
+	operation->response->header->result = gb_operation_errno_map(errno);
+
+	ret = gb_message_send(operation->response, GFP_KERNEL);
+	if (ret)
+		goto err_put_active;
+
+	return 0;
+
+err_put_active:
+	gb_operation_put_active(operation);
+err_put:
+	gb_operation_put(operation);
+
+	return ret;
+}
+
+/*
+ * This function is called when a message send request has completed.
+ */
+void greybus_message_sent(struct gb_host_device *hd,
+					struct gb_message *message, int status)
+{
+	struct gb_operation *operation = message->operation;
+	struct gb_connection *connection = operation->connection;
+
+	/*
+	 * If the message was a response, we just need to drop our
+	 * reference to the operation.  If an error occurred, report
+	 * it.
+	 *
+	 * For requests, if there's no error and the operation in not
+	 * unidirectional, there's nothing more to do until the response
+	 * arrives. If an error occurred attempting to send it, or if the
+	 * operation is unidrectional, record the result of the operation and
+	 * schedule its completion.
+	 */
+	if (message == operation->response) {
+		if (status) {
+			dev_err(&connection->hd->dev,
+				"%s: error sending response 0x%02x: %d\n",
+				connection->name, operation->type, status);
+		}
+
+		gb_operation_put_active(operation);
+		gb_operation_put(operation);
+	} else if (status || gb_operation_is_unidirectional(operation)) {
+		if (gb_operation_result_set(operation, status)) {
+			queue_work(gb_operation_completion_wq,
+					&operation->work);
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(greybus_message_sent);
+
+/*
+ * We've received data on a connection, and it doesn't look like a
+ * response, so we assume it's a request.
+ *
+ * This is called in interrupt context, so just copy the incoming
+ * data into the request buffer and handle the rest via workqueue.
+ */
+static void gb_connection_recv_request(struct gb_connection *connection,
+				const struct gb_operation_msg_hdr *header,
+				void *data, size_t size)
+{
+	struct gb_operation *operation;
+	u16 operation_id;
+	u8 type;
+	int ret;
+
+	operation_id = le16_to_cpu(header->operation_id);
+	type = header->type;
+
+	operation = gb_operation_create_incoming(connection, operation_id,
+						type, data, size);
+	if (!operation) {
+		dev_err(&connection->hd->dev,
+			"%s: can't create incoming operation\n",
+			connection->name);
+		return;
+	}
+
+	ret = gb_operation_get_active(operation);
+	if (ret) {
+		gb_operation_put(operation);
+		return;
+	}
+	trace_gb_message_recv_request(operation->request);
+
+	/*
+	 * The initial reference to the operation will be dropped when the
+	 * request handler returns.
+	 */
+	if (gb_operation_result_set(operation, -EINPROGRESS))
+		queue_work(connection->wq, &operation->work);
+}
+
+/*
+ * We've received data that appears to be an operation response
+ * message.  Look up the operation, and record that we've received
+ * its response.
+ *
+ * This is called in interrupt context, so just copy the incoming
+ * data into the response buffer and handle the rest via workqueue.
+ */
+static void gb_connection_recv_response(struct gb_connection *connection,
+				const struct gb_operation_msg_hdr *header,
+				void *data, size_t size)
+{
+	struct gb_operation *operation;
+	struct gb_message *message;
+	size_t message_size;
+	u16 operation_id;
+	int errno;
+
+	operation_id = le16_to_cpu(header->operation_id);
+
+	if (!operation_id) {
+		dev_err_ratelimited(&connection->hd->dev,
+				"%s: invalid response id 0 received\n",
+				connection->name);
+		return;
+	}
+
+	operation = gb_operation_find_outgoing(connection, operation_id);
+	if (!operation) {
+		dev_err_ratelimited(&connection->hd->dev,
+				"%s: unexpected response id 0x%04x received\n",
+				connection->name, operation_id);
+		return;
+	}
+
+	errno = gb_operation_status_map(header->result);
+	message = operation->response;
+	message_size = sizeof(*header) + message->payload_size;
+	if (!errno && size > message_size) {
+		dev_err_ratelimited(&connection->hd->dev,
+				"%s: malformed response 0x%02x received (%zu > %zu)\n",
+				connection->name, header->type,
+				size, message_size);
+		errno = -EMSGSIZE;
+	} else if (!errno && size < message_size) {
+		if (gb_operation_short_response_allowed(operation)) {
+			message->payload_size = size - sizeof(*header);
+		} else {
+			dev_err_ratelimited(&connection->hd->dev,
+					"%s: short response 0x%02x received (%zu < %zu)\n",
+					connection->name, header->type,
+					size, message_size);
+			errno = -EMSGSIZE;
+		}
+	}
+
+	/* We must ignore the payload if a bad status is returned */
+	if (errno)
+		size = sizeof(*header);
+
+	/* The rest will be handled in work queue context */
+	if (gb_operation_result_set(operation, errno)) {
+		memcpy(message->buffer, data, size);
+
+		trace_gb_message_recv_response(message);
+
+		queue_work(gb_operation_completion_wq, &operation->work);
+	}
+
+	gb_operation_put(operation);
+}
+
+/*
+ * Handle data arriving on a connection.  As soon as we return the
+ * supplied data buffer will be reused (so unless we do something
+ * with, it's effectively dropped).
+ */
+void gb_connection_recv(struct gb_connection *connection,
+				void *data, size_t size)
+{
+	struct gb_operation_msg_hdr header;
+	struct device *dev = &connection->hd->dev;
+	size_t msg_size;
+
+	if (connection->state == GB_CONNECTION_STATE_DISABLED ||
+			gb_connection_is_offloaded(connection)) {
+		dev_warn_ratelimited(dev, "%s: dropping %zu received bytes\n",
+				connection->name, size);
+		return;
+	}
+
+	if (size < sizeof(header)) {
+		dev_err_ratelimited(dev, "%s: short message received\n",
+				connection->name);
+		return;
+	}
+
+	/* Use memcpy as data may be unaligned */
+	memcpy(&header, data, sizeof(header));
+	msg_size = le16_to_cpu(header.size);
+	if (size < msg_size) {
+		dev_err_ratelimited(dev,
+				"%s: incomplete message 0x%04x of type 0x%02x received (%zu < %zu)\n",
+				connection->name,
+				le16_to_cpu(header.operation_id),
+				header.type, size, msg_size);
+		return;		/* XXX Should still complete operation */
+	}
+
+	if (header.type & GB_MESSAGE_TYPE_RESPONSE) {
+		gb_connection_recv_response(connection,	&header, data,
+						msg_size);
+	} else {
+		gb_connection_recv_request(connection, &header, data,
+						msg_size);
+	}
+}
+
+/*
+ * Cancel an outgoing operation synchronously, and record the given error to
+ * indicate why.
+ */
+void gb_operation_cancel(struct gb_operation *operation, int errno)
+{
+	if (WARN_ON(gb_operation_is_incoming(operation)))
+		return;
+
+	if (gb_operation_result_set(operation, errno)) {
+		gb_message_cancel(operation->request);
+		queue_work(gb_operation_completion_wq, &operation->work);
+	}
+	trace_gb_message_cancel_outgoing(operation->request);
+
+	atomic_inc(&operation->waiters);
+	wait_event(gb_operation_cancellation_queue,
+			!gb_operation_is_active(operation));
+	atomic_dec(&operation->waiters);
+}
+EXPORT_SYMBOL_GPL(gb_operation_cancel);
+
+/*
+ * Cancel an incoming operation synchronously. Called during connection tear
+ * down.
+ */
+void gb_operation_cancel_incoming(struct gb_operation *operation, int errno)
+{
+	if (WARN_ON(!gb_operation_is_incoming(operation)))
+		return;
+
+	if (!gb_operation_is_unidirectional(operation)) {
+		/*
+		 * Make sure the request handler has submitted the response
+		 * before cancelling it.
+		 */
+		flush_work(&operation->work);
+		if (!gb_operation_result_set(operation, errno))
+			gb_message_cancel(operation->response);
+	}
+	trace_gb_message_cancel_incoming(operation->response);
+
+	atomic_inc(&operation->waiters);
+	wait_event(gb_operation_cancellation_queue,
+			!gb_operation_is_active(operation));
+	atomic_dec(&operation->waiters);
+}
+
+/**
+ * gb_operation_sync_timeout() - implement a "simple" synchronous operation
+ * @connection: the Greybus connection to send this to
+ * @type: the type of operation to send
+ * @request: pointer to a memory buffer to copy the request from
+ * @request_size: size of @request
+ * @response: pointer to a memory buffer to copy the response to
+ * @response_size: the size of @response.
+ * @timeout: operation timeout in milliseconds
+ *
+ * This function implements a simple synchronous Greybus operation.  It sends
+ * the provided operation request and waits (sleeps) until the corresponding
+ * operation response message has been successfully received, or an error
+ * occurs.  @request and @response are buffers to hold the request and response
+ * data respectively, and if they are not NULL, their size must be specified in
+ * @request_size and @response_size.
+ *
+ * If a response payload is to come back, and @response is not NULL,
+ * @response_size number of bytes will be copied into @response if the operation
+ * is successful.
+ *
+ * If there is an error, the response buffer is left alone.
+ */
+int gb_operation_sync_timeout(struct gb_connection *connection, int type,
+				void *request, int request_size,
+				void *response, int response_size,
+				unsigned int timeout)
+{
+	struct gb_operation *operation;
+	int ret;
+
+	if ((response_size && !response) ||
+	    (request_size && !request))
+		return -EINVAL;
+
+	operation = gb_operation_create(connection, type,
+					request_size, response_size,
+					GFP_KERNEL);
+	if (!operation)
+		return -ENOMEM;
+
+	if (request_size)
+		memcpy(operation->request->payload, request, request_size);
+
+	ret = gb_operation_request_send_sync_timeout(operation, timeout);
+	if (ret) {
+		dev_err(&connection->hd->dev,
+			"%s: synchronous operation id 0x%04x of type 0x%02x failed: %d\n",
+			connection->name, operation->id, type, ret);
+	} else {
+		if (response_size) {
+			memcpy(response, operation->response->payload,
+			       response_size);
+		}
+	}
+
+	gb_operation_put(operation);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gb_operation_sync_timeout);
+
+/**
+ * gb_operation_unidirectional_timeout() - initiate a unidirectional operation
+ * @connection:		connection to use
+ * @type:		type of operation to send
+ * @request:		memory buffer to copy the request from
+ * @request_size:	size of @request
+ * @timeout:		send timeout in milliseconds
+ *
+ * Initiate a unidirectional operation by sending a request message and
+ * waiting for it to be acknowledged as sent by the host device.
+ *
+ * Note that successful send of a unidirectional operation does not imply that
+ * the request as actually reached the remote end of the connection.
+ */
+int gb_operation_unidirectional_timeout(struct gb_connection *connection,
+				int type, void *request, int request_size,
+				unsigned int timeout)
+{
+	struct gb_operation *operation;
+	int ret;
+
+	if (request_size && !request)
+		return -EINVAL;
+
+	operation = gb_operation_create_flags(connection, type,
+					request_size, 0,
+					GB_OPERATION_FLAG_UNIDIRECTIONAL,
+					GFP_KERNEL);
+	if (!operation)
+		return -ENOMEM;
+
+	if (request_size)
+		memcpy(operation->request->payload, request, request_size);
+
+	ret = gb_operation_request_send_sync_timeout(operation, timeout);
+	if (ret) {
+		dev_err(&connection->hd->dev,
+			"%s: unidirectional operation of type 0x%02x failed: %d\n",
+			connection->name, type, ret);
+	}
+
+	gb_operation_put(operation);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gb_operation_unidirectional_timeout);
+
+int __init gb_operation_init(void)
+{
+	gb_message_cache = kmem_cache_create("gb_message_cache",
+				sizeof(struct gb_message), 0, 0, NULL);
+	if (!gb_message_cache)
+		return -ENOMEM;
+
+	gb_operation_cache = kmem_cache_create("gb_operation_cache",
+				sizeof(struct gb_operation), 0, 0, NULL);
+	if (!gb_operation_cache)
+		goto err_destroy_message_cache;
+
+	gb_operation_completion_wq = alloc_workqueue("greybus_completion",
+				0, 0);
+	if (!gb_operation_completion_wq)
+		goto err_destroy_operation_cache;
+
+	return 0;
+
+err_destroy_operation_cache:
+	kmem_cache_destroy(gb_operation_cache);
+	gb_operation_cache = NULL;
+err_destroy_message_cache:
+	kmem_cache_destroy(gb_message_cache);
+	gb_message_cache = NULL;
+
+	return -ENOMEM;
+}
+
+void gb_operation_exit(void)
+{
+	destroy_workqueue(gb_operation_completion_wq);
+	gb_operation_completion_wq = NULL;
+	kmem_cache_destroy(gb_operation_cache);
+	gb_operation_cache = NULL;
+	kmem_cache_destroy(gb_message_cache);
+	gb_message_cache = NULL;
+}
--- /dev/null
+++ b/drivers/greybus/operation.h
@@ -0,0 +1,210 @@
+/*
+ * Greybus operations
+ *
+ * Copyright 2014 Google Inc.
+ * Copyright 2014 Linaro Ltd.
+ *
+ * Released under the GPLv2 only.
+ */
+
+#ifndef __OPERATION_H
+#define __OPERATION_H
+
+#include <linux/completion.h>
+
+struct gb_operation;
+
+/* The default amount of time a request is given to complete */
+#define GB_OPERATION_TIMEOUT_DEFAULT	1000	/* milliseconds */
+
+/*
+ * The top bit of the type in an operation message header indicates
+ * whether the message is a request (bit clear) or response (bit set)
+ */
+#define GB_MESSAGE_TYPE_RESPONSE	((u8)0x80)
+
+enum gb_operation_result {
+	GB_OP_SUCCESS		= 0x00,
+	GB_OP_INTERRUPTED	= 0x01,
+	GB_OP_TIMEOUT		= 0x02,
+	GB_OP_NO_MEMORY		= 0x03,
+	GB_OP_PROTOCOL_BAD	= 0x04,
+	GB_OP_OVERFLOW		= 0x05,
+	GB_OP_INVALID		= 0x06,
+	GB_OP_RETRY		= 0x07,
+	GB_OP_NONEXISTENT	= 0x08,
+	GB_OP_UNKNOWN_ERROR	= 0xfe,
+	GB_OP_MALFUNCTION	= 0xff,
+};
+
+#define GB_OPERATION_MESSAGE_SIZE_MIN	sizeof(struct gb_operation_msg_hdr)
+#define GB_OPERATION_MESSAGE_SIZE_MAX	U16_MAX
+
+/*
+ * Protocol code should only examine the payload and payload_size fields, and
+ * host-controller drivers may use the hcpriv field. All other fields are
+ * intended to be private to the operations core code.
+ */
+struct gb_message {
+	struct gb_operation		*operation;
+	struct gb_operation_msg_hdr	*header;
+
+	void				*payload;
+	size_t				payload_size;
+
+	void				*buffer;
+
+	void				*hcpriv;
+};
+
+#define GB_OPERATION_FLAG_INCOMING		BIT(0)
+#define GB_OPERATION_FLAG_UNIDIRECTIONAL	BIT(1)
+#define GB_OPERATION_FLAG_SHORT_RESPONSE	BIT(2)
+#define GB_OPERATION_FLAG_CORE			BIT(3)
+
+#define GB_OPERATION_FLAG_USER_MASK	(GB_OPERATION_FLAG_SHORT_RESPONSE | \
+					 GB_OPERATION_FLAG_UNIDIRECTIONAL)
+
+/*
+ * A Greybus operation is a remote procedure call performed over a
+ * connection between two UniPro interfaces.
+ *
+ * Every operation consists of a request message sent to the other
+ * end of the connection coupled with a reply message returned to
+ * the sender.  Every operation has a type, whose interpretation is
+ * dependent on the protocol associated with the connection.
+ *
+ * Only four things in an operation structure are intended to be
+ * directly usable by protocol handlers:  the operation's connection
+ * pointer; the operation type; the request message payload (and
+ * size); and the response message payload (and size).  Note that a
+ * message with a 0-byte payload has a null message payload pointer.
+ *
+ * In addition, every operation has a result, which is an errno
+ * value.  Protocol handlers access the operation result using
+ * gb_operation_result().
+ */
+typedef void (*gb_operation_callback)(struct gb_operation *);
+struct gb_operation {
+	struct gb_connection	*connection;
+	struct gb_message	*request;
+	struct gb_message	*response;
+
+	unsigned long		flags;
+	u8			type;
+	u16			id;
+	int			errno;		/* Operation result */
+
+	struct work_struct	work;
+	gb_operation_callback	callback;
+	struct completion	completion;
+
+	struct kref		kref;
+	atomic_t		waiters;
+
+	int			active;
+	struct list_head	links;		/* connection->operations */
+};
+
+static inline bool
+gb_operation_is_incoming(struct gb_operation *operation)
+{
+	return operation->flags & GB_OPERATION_FLAG_INCOMING;
+}
+
+static inline bool
+gb_operation_is_unidirectional(struct gb_operation *operation)
+{
+	return operation->flags & GB_OPERATION_FLAG_UNIDIRECTIONAL;
+}
+
+static inline bool
+gb_operation_short_response_allowed(struct gb_operation *operation)
+{
+	return operation->flags & GB_OPERATION_FLAG_SHORT_RESPONSE;
+}
+
+static inline bool gb_operation_is_core(struct gb_operation *operation)
+{
+	return operation->flags & GB_OPERATION_FLAG_CORE;
+}
+
+void gb_connection_recv(struct gb_connection *connection,
+					void *data, size_t size);
+
+int gb_operation_result(struct gb_operation *operation);
+
+size_t gb_operation_get_payload_size_max(struct gb_connection *connection);
+struct gb_operation *
+gb_operation_create_flags(struct gb_connection *connection,
+				u8 type, size_t request_size,
+				size_t response_size, unsigned long flags,
+				gfp_t gfp);
+
+static inline struct gb_operation *
+gb_operation_create(struct gb_connection *connection,
+				u8 type, size_t request_size,
+				size_t response_size, gfp_t gfp)
+{
+	return gb_operation_create_flags(connection, type, request_size,
+						response_size, 0, gfp);
+}
+
+struct gb_operation *
+gb_operation_create_core(struct gb_connection *connection,
+				u8 type, size_t request_size,
+				size_t response_size, unsigned long flags,
+				gfp_t gfp);
+
+void gb_operation_get(struct gb_operation *operation);
+void gb_operation_put(struct gb_operation *operation);
+
+bool gb_operation_response_alloc(struct gb_operation *operation,
+					size_t response_size, gfp_t gfp);
+
+int gb_operation_request_send(struct gb_operation *operation,
+				gb_operation_callback callback,
+				gfp_t gfp);
+int gb_operation_request_send_sync_timeout(struct gb_operation *operation,
+						unsigned int timeout);
+static inline int
+gb_operation_request_send_sync(struct gb_operation *operation)
+{
+	return gb_operation_request_send_sync_timeout(operation,
+			GB_OPERATION_TIMEOUT_DEFAULT);
+}
+
+void gb_operation_cancel(struct gb_operation *operation, int errno);
+void gb_operation_cancel_incoming(struct gb_operation *operation, int errno);
+
+void greybus_message_sent(struct gb_host_device *hd,
+				struct gb_message *message, int status);
+
+int gb_operation_sync_timeout(struct gb_connection *connection, int type,
+				void *request, int request_size,
+				void *response, int response_size,
+				unsigned int timeout);
+int gb_operation_unidirectional_timeout(struct gb_connection *connection,
+				int type, void *request, int request_size,
+				unsigned int timeout);
+
+static inline int gb_operation_sync(struct gb_connection *connection, int type,
+		      void *request, int request_size,
+		      void *response, int response_size)
+{
+	return gb_operation_sync_timeout(connection, type,
+			request, request_size, response, response_size,
+			GB_OPERATION_TIMEOUT_DEFAULT);
+}
+
+static inline int gb_operation_unidirectional(struct gb_connection *connection,
+				int type, void *request, int request_size)
+{
+	return gb_operation_unidirectional_timeout(connection, type,
+			request, request_size, GB_OPERATION_TIMEOUT_DEFAULT);
+}
+
+int gb_operation_init(void);
+void gb_operation_exit(void);
+
+#endif /* !__OPERATION_H */