[PATCH net-next 10/12] skbuff: allow 2-4-argument skb_frag_dma_map()

[Alexander Lobakin <aleksander.lobakin@intel.com>]

skb_frag_dma_map(dev, frag, 0, skb_frag_size(frag), DMA_TO_DEVICE)
is repeated across dozens of drivers and really wants a shorthand.
Add a macro which will count args and handle all possible number
from 2 to 5. Semantics:

skb_frag_dma_map(dev, frag) ->
__skb_frag_dma_map(dev, frag, 0, skb_frag_size(frag), DMA_TO_DEVICE)

skb_frag_dma_map(dev, frag, offset) ->
__skb_frag_dma_map(dev, frag, offset, skb_frag_size(frag) - offset,
		   DMA_TO_DEVICE)

skb_frag_dma_map(dev, frag, offset, size) ->
__skb_frag_dma_map(dev, frag, offset, size, DMA_TO_DEVICE)

skb_frag_dma_map(dev, frag, offset, size, dir) ->
__skb_frag_dma_map(dev, frag, offset, size, dir)

No object code size changes for the existing callers. Users passing
less arguments also won't have bigger size comparing to the full
equivalent call.

Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 include/linux/skbuff.h | 31 ++++++++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 8bcf14ae6789..bb2b751d274a 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3682,7 +3682,7 @@ static inline void skb_frag_page_copy(skb_frag_t *fragto,
 bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t prio);
 
 /**
- * skb_frag_dma_map - maps a paged fragment via the DMA API
+ * __skb_frag_dma_map - maps a paged fragment via the DMA API
  * @dev: the device to map the fragment to
  * @frag: the paged fragment to map
  * @offset: the offset within the fragment (starting at the
@@ -3692,15 +3692,36 @@ bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t prio);
  *
  * Maps the page associated with @frag to @device.
  */
-static inline dma_addr_t skb_frag_dma_map(struct device *dev,
-					  const skb_frag_t *frag,
-					  size_t offset, size_t size,
-					  enum dma_data_direction dir)
+static inline dma_addr_t __skb_frag_dma_map(struct device *dev,
+					    const skb_frag_t *frag,
+					    size_t offset, size_t size,
+					    enum dma_data_direction dir)
 {
 	return dma_map_page(dev, skb_frag_page(frag),
 			    skb_frag_off(frag) + offset, size, dir);
 }
 
+#define skb_frag_dma_map(dev, frag, ...)				\
+	CONCATENATE(_skb_frag_dma_map,					\
+		    COUNT_ARGS(__VA_ARGS__))(dev, frag, ##__VA_ARGS__)
+
+#define __skb_frag_dma_map1(dev, frag, offset, uf, uo) ({		\
+	const skb_frag_t *uf = (frag);					\
+	size_t uo = (offset);						\
+									\
+	__skb_frag_dma_map(dev, uf, uo, skb_frag_size(uf) - uo,		\
+			   DMA_TO_DEVICE);				\
+})
+#define _skb_frag_dma_map1(dev, frag, offset)				\
+	__skb_frag_dma_map1(dev, frag, offset, __UNIQUE_ID(frag_),	\
+			    __UNIQUE_ID(offset_))
+#define _skb_frag_dma_map0(dev, frag)					\
+	_skb_frag_dma_map1(dev, frag, 0)
+#define _skb_frag_dma_map2(dev, frag, offset, size)			\
+	__skb_frag_dma_map(dev, frag, offset, size, DMA_TO_DEVICE)
+#define _skb_frag_dma_map3(dev, frag, offset, size, dir)		\
+	__skb_frag_dma_map(dev, frag, offset, size, dir)
+
 static inline struct sk_buff *pskb_copy(struct sk_buff *skb,
 					gfp_t gfp_mask)
 {
-- 
2.47.1