path: root/drivers/greybus/operation.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Greybus operations
 *
 * Copyright 2014-2015 Google Inc.
 * Copyright 2014-2015 Linaro Ltd.
 */

#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 <linux/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) {
		/*