'bus_set_iommu()' allows IOMMU drivers to register their ops for a given
bus type. Unfortunately, it then doesn't allow them to be removed, which
is necessary for modular drivers to shutdown cleanly so that they can be
reloaded later on.

Allow 'bus_set_iommu()' to take a NULL 'ops' argument, which clear the
ops pointer for the selected bus_type.

Signed-off-by: Will Deacon <[email protected]>
---
 drivers/iommu/iommu.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 4bfecfbbe2cf..e99704c2e06b 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1558,6 +1558,11 @@ int bus_set_iommu(struct bus_type *bus, const struct 
iommu_ops *ops)
 {
        int err;
 
+       if (ops == NULL) {
+               bus->iommu_ops = NULL;
+               return 0;
+       }
+
        if (bus->iommu_ops != NULL)
                return -EBUSY;
 
-- 
2.24.0.432.g9d3f5f5b63-goog

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