drivers/xen/grant-dma-iommu.c

   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
  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
  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
  54 static void 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
  62 static struct platform_driver grant_dma_iommu_driver = {
  63         .driver = {
  64                 .name = "grant-dma-iommu",
  65                 .of_match_table = grant_dma_iommu_of_match,
  66         },
  67         .probe = grant_dma_iommu_probe,
  68         .remove_new = grant_dma_iommu_remove,
  69 };
  70
  71 static int __init grant_dma_iommu_init(void)
  72 {
  73         struct device_node *iommu_np;
  74
  75         iommu_np = of_find_matching_node(NULL, grant_dma_iommu_of_match);
  76         if (!iommu_np)
  77                 return 0;
  78
  79         of_node_put(iommu_np);
  80
  81         return platform_driver_register(&grant_dma_iommu_driver);
  82 }
  83 subsys_initcall(grant_dma_iommu_init);