Several RDMA drivers need to provide a DMA mapping API but use the
CPU to transfer data. Provide DMA mapping operations that are
suitable for these drivers.
Signed-off-by: Bart Van Assche <bart.vanass...@sandisk.com>
Cc: Christian Borntraeger <borntrae...@de.ibm.com>
Cc: Joerg Roedel <jroe...@suse.de>
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Michael S. Tsirkin <m...@redhat.com>
---
include/linux/dma-mapping.h | 1 +
lib/Kconfig | 5 ++++
lib/Makefile | 1 +
lib/dma-virt.c | 73 +++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 80 insertions(+)
create mode 100644 lib/dma-virt.c
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index ab8710888ddf..426c43d4fdbf 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -128,6 +128,7 @@ struct dma_map_ops {
};
extern const struct dma_map_ops dma_noop_ops;
+extern const struct dma_map_ops dma_virt_ops;
#define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
diff --git a/lib/Kconfig b/lib/Kconfig
index b6baf0609e8b..97af23b26f33 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -400,6 +400,11 @@ config DMA_NOOP_OPS
depends on HAS_DMA && (!64BIT || ARCH_DMA_ADDR_T_64BIT)
default n
+config DMA_VIRT_OPS
+ bool
+ depends on HAS_DMA && (!64BIT || ARCH_DMA_ADDR_T_64BIT)
+ default n
+
config CHECK_SIGNATURE
bool
diff --git a/lib/Makefile b/lib/Makefile
index ada06d5652e8..b97e9a814854 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -27,6 +27,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
lib-$(CONFIG_MMU) += ioremap.o
lib-$(CONFIG_SMP) += cpumask.o
lib-$(CONFIG_DMA_NOOP_OPS) += dma-noop.o
+lib-$(CONFIG_DMA_VIRT_OPS) += dma-virt.o
lib-y += kobject.o klist.o
obj-y += lockref.o
diff --git a/lib/dma-virt.c b/lib/dma-virt.c
new file mode 100644
index 000000000000..b3573b6ad5b1
--- /dev/null
+++ b/lib/dma-virt.c
@@ -0,0 +1,73 @@
+/*
+ * lib/dma-virt.c
+ *
+ * DMA operations that map to virtual addresses without flushing memory.
+ */
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/dma-mapping.h>
+#include <linux/scatterlist.h>
+
+static void *dma_virt_alloc(struct device *dev, size_t size,
+ dma_addr_t *dma_handle, gfp_t gfp,
+ unsigned long attrs)
+{
+ void *ret;
+
+ ret = (void *)__get_free_pages(gfp, get_order(size));
+ if (ret)
+ *dma_handle = (uintptr_t)ret;
+ return ret;
+}
+
+static void dma_virt_free(struct device *dev, size_t size,
+ void *cpu_addr, dma_addr_t dma_addr,
+ unsigned long attrs)
+{
+ free_pages((unsigned long)cpu_addr, get_order(size));
+}
+
+static dma_addr_t dma_virt_map_page(struct device *dev, struct page *page,
+ unsigned long offset, size_t size,
+ enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ return (uintptr_t)(page_address(page) + offset);
+}
+
+static int dma_virt_map_sg(struct device *dev, struct scatterlist *sgl, int
nents,
+ enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ int i;
+ struct scatterlist *sg;
+
+ for_each_sg(sgl, sg, nents, i) {
+ BUG_ON(!sg_page(sg));
+ sg_dma_address(sg) = (uintptr_t)sg_virt(sg);
+ sg_dma_len(sg) = sg->length;
+ }
+
+ return nents;
+}
+
+static int dma_virt_mapping_error(struct device *dev, dma_addr_t dma_addr)
+{
+ return false;
+}
+
+static int dma_virt_supported(struct device *dev, u64 mask)
+{
+ return true;
+}
+
+const struct dma_map_ops dma_virt_ops = {
+ .alloc = dma_virt_alloc,
+ .free = dma_virt_free,
+ .map_page = dma_virt_map_page,
+ .map_sg = dma_virt_map_sg,
+ .mapping_error = dma_virt_mapping_error,
+ .dma_supported = dma_virt_supported,
+};
+
+EXPORT_SYMBOL(dma_virt_ops);
--
2.11.0
