xref: /openbmc/linux/drivers/xen/grant-dma-iommu.c (revision 2062f9fb)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Stub IOMMU driver which does nothing.
4  * The main purpose of it being present is to reuse generic IOMMU device tree
5  * bindings by Xen grant DMA-mapping layer.
6  *
7  * Copyright (C) 2022 EPAM Systems Inc.
8  */
9 
10 #include <linux/iommu.h>
11 #include <linux/of.h>
12 #include <linux/platform_device.h>
13 
14 struct grant_dma_iommu_device {
15 	struct device *dev;
16 	struct iommu_device iommu;
17 };
18 
grant_dma_iommu_probe_device(struct device * dev)19 static struct iommu_device *grant_dma_iommu_probe_device(struct device *dev)
20 {
21 	return ERR_PTR(-ENODEV);
22 }
23 
24 /* Nothing is really needed here except a dummy probe_device callback */
25 static const struct iommu_ops grant_dma_iommu_ops = {
26 	.probe_device = grant_dma_iommu_probe_device,
27 };
28 
29 static const struct of_device_id grant_dma_iommu_of_match[] = {
30 	{ .compatible = "xen,grant-dma" },
31 	{ },
32 };
33 
grant_dma_iommu_probe(struct platform_device * pdev)34 static int grant_dma_iommu_probe(struct platform_device *pdev)
35 {
36 	struct grant_dma_iommu_device *mmu;
37 	int ret;
38 
39 	mmu = devm_kzalloc(&pdev->dev, sizeof(*mmu), GFP_KERNEL);
40 	if (!mmu)
41 		return -ENOMEM;
42 
43 	mmu->dev = &pdev->dev;
44 
45 	ret = iommu_device_register(&mmu->iommu, &grant_dma_iommu_ops, &pdev->dev);
46 	if (ret)
47 		return ret;
48 
49 	platform_set_drvdata(pdev, mmu);
50 
51 	return 0;
52 }
53 
grant_dma_iommu_remove(struct platform_device * pdev)54 static int grant_dma_iommu_remove(struct platform_device *pdev)
55 {
56 	struct grant_dma_iommu_device *mmu = platform_get_drvdata(pdev);
57 
58 	platform_set_drvdata(pdev, NULL);
59 	iommu_device_unregister(&mmu->iommu);
60 
61 	return 0;
62 }
63 
64 static struct platform_driver grant_dma_iommu_driver = {
65 	.driver = {
66 		.name = "grant-dma-iommu",
67 		.of_match_table = grant_dma_iommu_of_match,
68 	},
69 	.probe = grant_dma_iommu_probe,
70 	.remove = grant_dma_iommu_remove,
71 };
72 
grant_dma_iommu_init(void)73 static int __init grant_dma_iommu_init(void)
74 {
75 	struct device_node *iommu_np;
76 
77 	iommu_np = of_find_matching_node(NULL, grant_dma_iommu_of_match);
78 	if (!iommu_np)
79 		return 0;
80 
81 	of_node_put(iommu_np);
82 
83 	return platform_driver_register(&grant_dma_iommu_driver);
84 }
85 subsys_initcall(grant_dma_iommu_init);
86