[Xen-devel] [PATCH 03/15] [swiotlb] Add swiotlb_register_engine function.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

We set the internal iommu_sw pointer to the passed in swiotlb_engine
structure. Obviously we also check if the existing iommu_sw is
set and if so, call iommu_sw->release before the switch-over.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 include/linux/swiotlb.h |    2 +
 lib/swiotlb.c           |   48 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 0 deletions(-)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 781c3aa..3bc3c42 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -118,6 +118,8 @@ struct swiotlb_engine {
        void* (*bus_to_virt)(struct device *hwdev, dma_addr_t address);
 };
 
+int swiotlb_register_engine(struct swiotlb_engine *iommu);
+
 extern void
 *swiotlb_alloc_coherent(struct device *hwdev, size_t size,
                        dma_addr_t *dma_handle, gfp_t flags);
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index e6d9e32..e84f269 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -97,6 +97,12 @@ static phys_addr_t *io_tlb_orig_addr;
  */
 static DEFINE_SPINLOCK(io_tlb_lock);
 
+/*
+ * The software IOMMU this library will utilize.
+ */
+struct swiotlb_engine *iommu_sw;
+EXPORT_SYMBOL(iommu_sw);
+
 static int late_alloc;
 
 static int __init
@@ -126,6 +132,48 @@ static dma_addr_t swiotlb_virt_to_bus(struct device *hwdev,
        return phys_to_dma(hwdev, virt_to_phys(address));
 }
 
+/*
+ * Register a software IO TLB engine.
+ *
+ * The registration allows the software IO TLB functions in the
+ * swiotlb library to function properly.
+ *
+ * All the values in the iotlb structure must be set.
+ *
+ * If the registration fails, it is assumed that the caller will free
+ * all of the resources allocated in the swiotlb_engine structure.
+ */
+int swiotlb_register_engine(struct swiotlb_engine *iommu)
+{
+       if (!iommu || !iommu->name || !iommu->release) {
+               printk(KERN_ERR "DMA: Trying to register a SWIOTLB engine" \
+                               " improperly!");
+               return -EINVAL;
+       }
+
+       if (iommu_sw && iommu_sw->name) {
+               int retval = -EINVAL;
+
+               /* 'release' must check for out-standing DMAs and flush them
+                *  out or fail. */
+               if (iommu_sw->release)
+                       retval = iommu_sw->release(iommu_sw);
+
+               if (retval) {
+                       printk(KERN_ERR "DMA: %s cannot be released!\n",
+                               iommu_sw->name);
+                       return retval;
+               }
+               printk(KERN_INFO "DMA: Replacing [%s] with [%s]\n",
+                       iommu_sw->name, iommu->name);
+       }
+
+       iommu_sw = iommu;
+
+       return 0;
+}
+EXPORT_SYMBOL(swiotlb_register_engine);
+
 void swiotlb_print_info(void)
 {
        unsigned long bytes = io_tlb_nslabs << IO_TLB_SHIFT;
-- 
1.6.2.5


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