[PATCH v2 08/22] dma-mapping: Allow map_sg() ops to return negative error codes
From: Logan Gunthorpe
Date: Thu May 13 2021 - 18:33:11 EST
Allow dma_map_sgtable() to pass errors from the map_sg() ops. This
will be required for returning appropriate error codes when mapping
P2PDMA memory.
Introduce __dma_map_sg_attrs() which will return the raw error code
from the map_sg operation (whether it be negative or zero). Then add a
dma_map_sg_attrs() wrapper to convert any negative errors to zero to
satisfy the existing calling convention.
dma_map_sgtable() will convert a zero error return for old map_sg() ops
into a -EINVAL return and return any negative errors as reported.
This allows map_sg implementations to start returning multiple
negative error codes. Legacy map_sg implementations can continue
to return zero until they are all converted.
Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
---
include/linux/dma-map-ops.h | 8 ++++++--
include/linux/dma-mapping.h | 41 ++++++++++++++++++++++++++++++++-----
kernel/dma/mapping.c | 13 +++++-------
3 files changed, 47 insertions(+), 15 deletions(-)
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 0d53a96a3d64..eaa969be8284 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -41,8 +41,12 @@ struct dma_map_ops {
size_t size, enum dma_data_direction dir,
unsigned long attrs);
/*
- * map_sg returns 0 on error and a value > 0 on success.
- * It should never return a value < 0.
+ * map_sg should return a negative error code on error.
+ * dma_map_sgtable() will return the error code returned and convert
+ * a zero return (for legacy implementations) into -EINVAL.
+ *
+ * dma_map_sg() will always return zero on any negative or zero
+ * return to satisfy its own calling convention.
*/
int (*map_sg)(struct device *dev, struct scatterlist *sg, int nents,
enum dma_data_direction dir, unsigned long attrs);
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 183e7103a66d..2b0ecf0aa4df 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -105,7 +105,7 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
unsigned long attrs);
void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
enum dma_data_direction dir, unsigned long attrs);
-int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents,
+int __dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents,
enum dma_data_direction dir, unsigned long attrs);
void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
int nents, enum dma_data_direction dir,
@@ -164,7 +164,7 @@ static inline void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr,
size_t size, enum dma_data_direction dir, unsigned long attrs)
{
}
-static inline int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
+static inline int __dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
int nents, enum dma_data_direction dir, unsigned long attrs)
{
return 0;
@@ -343,6 +343,34 @@ static inline void dma_sync_single_range_for_device(struct device *dev,
return dma_sync_single_for_device(dev, addr + offset, size, dir);
}
+/**
+ * dma_map_sg_attrs - Map the given buffer for DMA
+ * @dev: The device for which to perform the DMA operation
+ * @sg: The sg_table object describing the buffer
+ * @dir: DMA direction
+ * @attrs: Optional DMA attributes for the map operation
+ *
+ * Maps a buffer described by a scatterlist passed in the sg argument with
+ * nents segments for the @dir DMA operation by the @dev device.
+ *
+ * Returns the number of mapped entries (which can be less than nents)
+ * on success. Zero is returned for any error.
+ *
+ * dma_unmap_sg_attrs() should be used to unmap the buffer with the
+ * original sg and original nents (not the value returned by this funciton).
+ */
+static inline int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
+ int nents, enum dma_data_direction dir, unsigned long attrs)
+{
+ int ret;
+
+ ret = __dma_map_sg_attrs(dev, sg, nents, dir, attrs);
+ if (ret < 0)
+ ret = 0;
+
+ return ret;
+}
+
/**
* dma_map_sgtable - Map the given buffer for DMA
* @dev: The device for which to perform the DMA operation
@@ -357,16 +385,19 @@ static inline void dma_sync_single_range_for_device(struct device *dev,
* ownership of the buffer back to the CPU domain before touching the
* buffer by the CPU.
*
- * Returns 0 on success or -EINVAL on error during mapping the buffer.
+ * Returns 0 on success or a negative error code on error
*/
static inline int dma_map_sgtable(struct device *dev, struct sg_table *sgt,
enum dma_data_direction dir, unsigned long attrs)
{
int nents;
- nents = dma_map_sg_attrs(dev, sgt->sgl, sgt->orig_nents, dir, attrs);
- if (nents <= 0)
+ nents = __dma_map_sg_attrs(dev, sgt->sgl, sgt->orig_nents, dir, attrs);
+ if (nents == 0)
return -EINVAL;
+ else if (nents < 0)
+ return nents;
+
sgt->nents = nents;
return 0;
}
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 2b06a809d0b9..700a2bb7cc9e 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -177,11 +177,7 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
}
EXPORT_SYMBOL(dma_unmap_page_attrs);
-/*
- * dma_maps_sg_attrs returns 0 on error and > 0 on success.
- * It should never return a value < 0.
- */
-int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents,
+int __dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents,
enum dma_data_direction dir, unsigned long attrs)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
@@ -197,12 +193,13 @@ int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents,
ents = dma_direct_map_sg(dev, sg, nents, dir, attrs);
else
ents = ops->map_sg(dev, sg, nents, dir, attrs);
- BUG_ON(ents < 0);
- debug_dma_map_sg(dev, sg, nents, ents, dir);
+
+ if (ents > 0)
+ debug_dma_map_sg(dev, sg, nents, ents, dir);
return ents;
}
-EXPORT_SYMBOL(dma_map_sg_attrs);
+EXPORT_SYMBOL(__dma_map_sg_attrs);
void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
int nents, enum dma_data_direction dir,
--
2.20.1