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Subject[PATCH -mm 01/11] add device_dma_parameters structure
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iommu code merges scatter/gather segments without considering a low
level driver's restrictions. The problem is that iommu code can't
access to the limitations because they are in request_queue.

This patch adds a new structure, device_dma_parameters, including dma
information. A pointer to device_dma_parameters is added to struct
device.

- there are only max_segment_size and segment_boundary_mask there but
we'll move more dma stuff in struct device (like dma_mask) to struct
device_dma_parameters later. segment_boundary_mask is not supported
yet.

- new accessors for the dma parameters are added. So we can easily
change where to place struct device_dma_parameters in the future.

- dma_get_max_seg_size returns 64K if dma_parms in struct device isn't
set up properly. 64K is the default max_segment_size in the block
layer.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
---
include/linux/device.h | 11 +++++++++++
include/linux/dma-mapping.h | 15 +++++++++++++++
2 files changed, 26 insertions(+), 0 deletions(-)
diff --git a/include/linux/device.h b/include/linux/device.h
index 2e15822..9eb883f 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -397,6 +397,15 @@ extern int devres_release_group(struct device *dev, void *id);
extern void *devm_kzalloc(struct device *dev, size_t size, gfp_t gfp);
extern void devm_kfree(struct device *dev, void *p);

+struct device_dma_parameters {
+ /*
+ * a low level driver may set these to teach IOMMU code about
+ * sg limitations.
+ */
+ unsigned int max_segment_size;
+ unsigned long segment_boundary_mask;
+};
+
struct device {
struct klist klist_children;
struct klist_node knode_parent; /* node in sibling list */
@@ -432,6 +441,8 @@ struct device {
64 bit addresses for consistent
allocations such descriptors. */

+ struct device_dma_parameters *dma_parms;
+
struct list_head dma_pools; /* dma pools (if dma'ble) */

struct dma_coherent_mem *dma_mem; /* internal for coherent mem
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 101a2d4..71972ca 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -60,6 +60,21 @@ static inline int is_device_dma_capable(struct device *dev)

extern u64 dma_get_required_mask(struct device *dev);

+static inline unsigned int dma_get_max_seg_size(struct device *dev)
+{
+ return dev->dma_parms ? dev->dma_parms->max_segment_size : 65536;
+}
+
+static inline unsigned int dma_set_max_seg_size(struct device *dev,
+ unsigned int size)
+{
+ if (dev->dma_parms) {
+ dev->dma_parms->max_segment_size = size;
+ return 0;
+ } else
+ return -EIO;
+}
+
/* flags for the coherent memory api */
#define DMA_MEMORY_MAP 0x01
#define DMA_MEMORY_IO 0x02
--
1.5.2.4
-
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