include/linux/irqbypass.h

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * IRQ offload/bypass manager
 *
 * Copyright (C) 2015 Red Hat, Inc.
 * Copyright (c) 2015 Linaro Ltd.
 */
#ifndef IRQBYPASS_H
#define IRQBYPASS_H

#include <linux/list.h>

struct eventfd_ctx;
struct irq_bypass_consumer;

/*
 * Theory of operation
 *
 * The IRQ bypass manager is a simple set of lists and callbacks that allows
 * IRQ producers (ex. physical interrupt sources) to be matched to IRQ
 * consumers (ex. virtualization hardware that allows IRQ bypass or offload)
 * via a shared eventfd_ctx.  Producers and consumers register independently.
 * When a producer and consumer are paired, i.e. an eventfd match is found, the
 * optional @stop callback will be called for each participant.  The pair will
 * then be connected via the @add_* callbacks, and finally the optional @start
 * callback will allow any final coordination.  When either participant is
 * unregistered, the process is repeated using the @del_* callbacks in place of
 * the @add_* callbacks.  eventfds must be unique per producer/consumer, 1:N
 * pairings are not supported.
 */

struct irq_bypass_consumer;

/**
 * struct irq_bypass_producer - IRQ bypass producer definition
 * @eventfd: eventfd context used to match producers and consumers
 * @consumer: The connected consumer (NULL if no connection)
 * @irq: Linux IRQ number for the producer device
 * @add_consumer: Connect the IRQ producer to an IRQ consumer (optional)
 * @del_consumer: Disconnect the IRQ producer from an IRQ consumer (optional)
 * @stop: Perform any quiesce operations necessary prior to add/del (optional)
 * @start: Perform any startup operations necessary after add/del (optional)
 *
 * The IRQ bypass producer structure represents an interrupt source for
 * participation in possible host bypass, for instance an interrupt vector
 * for a physical device assigned to a VM.
 */
struct irq_bypass_producer {
	struct eventfd_ctx *eventfd;
	struct irq_bypass_consumer *consumer;
	int irq;
	int (*add_consumer)(struct irq_bypass_producer *,
			    struct irq_bypass_consumer *);
	void (*del_consumer)(struct irq_bypass_producer *,
			     struct irq_bypass_consumer *);
	void (*stop)(struct irq_bypass_producer *);
	void (*start)(struct irq_bypass_producer *);
};

/**
 * struct irq_bypass_consumer - IRQ bypass consumer definition
 * @eventfd: eventfd context used to match producers and consumers
 * @producer: The connected producer (NULL if no connection)
 * @add_producer: Connect the IRQ consumer to an IRQ producer
 * @del_producer: Disconnect the IRQ consumer from an IRQ producer
 * @stop: Perform any quiesce operations necessary prior to add/del (optional)
 * @start: Perform any startup operations necessary after add/del (optional)
 *
 * The IRQ bypass consumer structure represents an interrupt sink for
 * participation in possible host bypass, for instance a hypervisor may
 * support offloads to allow bypassing the host entirely or offload
 * portions of the interrupt handling to the VM.
 */
struct irq_bypass_consumer {
	struct eventfd_ctx *eventfd;
	struct irq_bypass_producer *producer;

	int (*add_producer)(struct irq_bypass_consumer *,
			    struct irq_bypass_producer *);
	void (*del_producer)(struct irq_bypass_consumer *,
			     struct irq_bypass_producer *);
	void (*stop)(struct irq_bypass_consumer *);
	void (*start)(struct irq_bypass_consumer *);
};

int irq_bypass_register_producer(struct irq_bypass_producer *producer,
				 struct eventfd_ctx *eventfd, int irq);
void irq_bypass_unregister_producer(struct irq_bypass_producer *producer);
int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer,
				 struct eventfd_ctx *eventfd);
void irq_bypass_unregister_consumer(struct irq_bypass_consumer *consumer);

#endif /* IRQBYPASS_H */