1/*
 2 * Copyright (c) 2016 Christoph Hellwig.
 3 *
 4 * This program is free software; you can redistribute it and/or modify it
 5 * under the terms and conditions of the GNU General Public License,
 6 * version 2, as published by the Free Software Foundation.
 7 *
 8 * This program is distributed in the hope it will be useful, but WITHOUT
 9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
11 * more details.
12 */
13#include <linux/kobject.h>
14#include <linux/blkdev.h>
15#include <linux/blk-mq.h>
16#include <linux/blk-mq-pci.h>
17#include <linux/pci.h>
18#include <linux/module.h>
19
20/**
21 * blk_mq_pci_map_queues - provide a default queue mapping for PCI device
22 * @set:	tagset to provide the mapping for
23 * @pdev:	PCI device associated with @set.
24 * @offset:	Offset to use for the pci irq vector
25 *
26 * This function assumes the PCI device @pdev has at least as many available
27 * interrupt vectors as @set has queues.  It will then query the vector
28 * corresponding to each queue for it's affinity mask and built queue mapping
29 * that maps a queue to the CPUs that have irq affinity for the corresponding
30 * vector.
31 */
32int blk_mq_pci_map_queues(struct blk_mq_tag_set *set, struct pci_dev *pdev,
33			    int offset)
34{
35	const struct cpumask *mask;
36	unsigned int queue, cpu;
37
38	for (queue = 0; queue < set->nr_hw_queues; queue++) {
39		mask = pci_irq_get_affinity(pdev, queue + offset);
40		if (!mask)
41			goto fallback;
42
43		for_each_cpu(cpu, mask)
44			set->mq_map[cpu] = queue;
45	}
46
47	return 0;
48
49fallback:
50	WARN_ON_ONCE(set->nr_hw_queues > 1);
51	for_each_possible_cpu(cpu)
52		set->mq_map[cpu] = 0;
53	return 0;
54}
55EXPORT_SYMBOL_GPL(blk_mq_pci_map_queues);