dma-mapping: factor out dummy DMA ops

The dummy DMA ops are currently used by arm64 for any device which has
an invalid ACPI description and is thus barred from using DMA due to not
knowing whether is is cache-coherent or not. Factor these out into
general dma-mapping code so that they can be referenced from other
common code paths. In the process, we can prune all the optional
callbacks which just do the same thing as the default behaviour, and
fill in .map_resource for completeness.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
[hch: moved to a separate source file]
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Tested-by: Jesper Dangaard Brouer <brouer@redhat.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h
index c41f3fb1446cec797ccea57f7dbcaaf5472ea3c5..273e778f7de28b951c00b82dd75721582080a79f 100644 (file)
--- a/arch/arm64/include/asm/dma-mapping.h
+++ b/arch/arm64/include/asm/dma-mapping.h
@@ -24,15 +24,13 @@
 #include <xen/xen.h>
 #include <asm/xen/hypervisor.h>
 
-extern const struct dma_map_ops dummy_dma_ops;
-
 static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
 {
        /*
         * We expect no ISA devices, and all other DMA masters are expected to
         * have someone call arch_setup_dma_ops at device creation time.
         */
-       return &dummy_dma_ops;
+       return &dma_dummy_ops;
 }
 
 void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 4c0f498069e8e0e80ea0cf8d7bbf182a46c742a2..6ff6ec8806c1870d22aeb8e1d44d630004956027 100644 (file)
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -89,92 +89,6 @@ static int __swiotlb_mmap_pfn(struct vm_area_struct *vma,
 }
 #endif /* CONFIG_IOMMU_DMA */
 
-/********************************************
- * The following APIs are for dummy DMA ops *
- ********************************************/
-
-static void *__dummy_alloc(struct device *dev, size_t size,
-                          dma_addr_t *dma_handle, gfp_t flags,
-                          unsigned long attrs)
-{
-       return NULL;
-}
-
-static void __dummy_free(struct device *dev, size_t size,
-                        void *vaddr, dma_addr_t dma_handle,
-                        unsigned long attrs)
-{
-}
-
-static int __dummy_mmap(struct device *dev,
-                       struct vm_area_struct *vma,
-                       void *cpu_addr, dma_addr_t dma_addr, size_t size,
-                       unsigned long attrs)
-{
-       return -ENXIO;
-}
-
-static dma_addr_t __dummy_map_page(struct device *dev, struct page *page,
-                                  unsigned long offset, size_t size,
-                                  enum dma_data_direction dir,
-                                  unsigned long attrs)
-{
-       return DMA_MAPPING_ERROR;
-}
-
-static void __dummy_unmap_page(struct device *dev, dma_addr_t dev_addr,
-                              size_t size, enum dma_data_direction dir,
-                              unsigned long attrs)
-{
-}
-
-static int __dummy_map_sg(struct device *dev, struct scatterlist *sgl,
-                         int nelems, enum dma_data_direction dir,
-                         unsigned long attrs)
-{
-       return 0;
-}
-
-static void __dummy_unmap_sg(struct device *dev,
-                            struct scatterlist *sgl, int nelems,
-                            enum dma_data_direction dir,
-                            unsigned long attrs)
-{
-}
-
-static void __dummy_sync_single(struct device *dev,
-                               dma_addr_t dev_addr, size_t size,
-                               enum dma_data_direction dir)
-{
-}
-
-static void __dummy_sync_sg(struct device *dev,
-                           struct scatterlist *sgl, int nelems,
-                           enum dma_data_direction dir)
-{
-}
-
-static int __dummy_dma_supported(struct device *hwdev, u64 mask)
-{
-       return 0;
-}
-
-const struct dma_map_ops dummy_dma_ops = {
-       .alloc                  = __dummy_alloc,
-       .free                   = __dummy_free,
-       .mmap                   = __dummy_mmap,
-       .map_page               = __dummy_map_page,
-       .unmap_page             = __dummy_unmap_page,
-       .map_sg                 = __dummy_map_sg,
-       .unmap_sg               = __dummy_unmap_sg,
-       .sync_single_for_cpu    = __dummy_sync_single,
-       .sync_single_for_device = __dummy_sync_single,
-       .sync_sg_for_cpu        = __dummy_sync_sg,
-       .sync_sg_for_device     = __dummy_sync_sg,
-       .dma_supported          = __dummy_dma_supported,
-};
-EXPORT_SYMBOL(dummy_dma_ops);
-
 static int __init arm64_dma_init(void)
 {
        WARN_TAINT(ARCH_DMA_MINALIGN < cache_line_size(),

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 0f0078490df492c8ab60f618ccfd089f190e00d0..269ee27fc3d9867a241d134a7e14252929287cba 100644 (file)
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -136,6 +136,7 @@ struct dma_map_ops {
 
 extern const struct dma_map_ops dma_direct_ops;
 extern const struct dma_map_ops dma_virt_ops;
+extern const struct dma_map_ops dma_dummy_ops;
 
 #define DMA_BIT_MASK(n)        (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
 

diff --git a/kernel/dma/Makefile b/kernel/dma/Makefile
index a626f643cd6325af1aab3824e9aad8f27cf1ee20..72ff6e46aa866d02b2cbeab2bdc91c5d00f496f6 100644 (file)
--- a/kernel/dma/Makefile
+++ b/kernel/dma/Makefile
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 
-obj-$(CONFIG_HAS_DMA)                  += mapping.o direct.o
+obj-$(CONFIG_HAS_DMA)                  += mapping.o direct.o dummy.o
 obj-$(CONFIG_DMA_CMA)                  += contiguous.o
 obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += coherent.o
 obj-$(CONFIG_DMA_VIRT_OPS)             += virt.o

diff --git a/kernel/dma/dummy.c b/kernel/dma/dummy.c
new file mode 100644 (file)
index 0000000..0560764
--- /dev/null
+++ b/kernel/dma/dummy.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Dummy DMA ops that always fail.
+ */
+#include <linux/dma-mapping.h>
+
+static int dma_dummy_mmap(struct device *dev, struct vm_area_struct *vma,
+               void *cpu_addr, dma_addr_t dma_addr, size_t size,
+               unsigned long attrs)
+{
+       return -ENXIO;
+}
+
+static dma_addr_t dma_dummy_map_page(struct device *dev, struct page *page,
+               unsigned long offset, size_t size, enum dma_data_direction dir,
+               unsigned long attrs)
+{
+       return DMA_MAPPING_ERROR;
+}
+
+static int dma_dummy_map_sg(struct device *dev, struct scatterlist *sgl,
+               int nelems, enum dma_data_direction dir,
+               unsigned long attrs)
+{
+       return 0;
+}
+
+static int dma_dummy_supported(struct device *hwdev, u64 mask)
+{
+       return 0;
+}
+
+const struct dma_map_ops dma_dummy_ops = {
+       .mmap                   = dma_dummy_mmap,
+       .map_page               = dma_dummy_map_page,
+       .map_sg                 = dma_dummy_map_sg,
+       .dma_supported          = dma_dummy_supported,
+};
+EXPORT_SYMBOL(dma_dummy_ops);