[PATCH v6 12/17] scatterlist: Add dedicated config for DMA flags

[Catalin Marinas <catalin.marinas@arm.com>]

From: Robin Murphy <robin.murphy@arm.com>

The DMA flags field will be useful for users beyond PCI P2P, so upgrade
to its own dedicated config option.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
[catalin.marinas@arm.com: use #ifdef CONFIG_NEED_SG_DMA_FLAGS in scatterlist.h]
[catalin.marinas@arm.com: update PCI_P2PDMA dma_flags comment in scatterlist.h]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 drivers/pci/Kconfig         |  1 +
 include/linux/scatterlist.h | 13 ++++++-------
 kernel/dma/Kconfig          |  3 +++
 3 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 9309f2469b41..3c07d8d214b3 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -168,6 +168,7 @@ config PCI_P2PDMA
 	#
 	depends on 64BIT
 	select GENERIC_ALLOCATOR
+	select NEED_SG_DMA_FLAGS
 	help
 	  Enableѕ drivers to do PCI peer-to-peer transactions to and from
 	  BARs that are exposed in other devices that are the part of
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 375a5e90d86a..19833fd4113b 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -16,7 +16,7 @@ struct scatterlist {
 #ifdef CONFIG_NEED_SG_DMA_LENGTH
 	unsigned int	dma_length;
 #endif
-#ifdef CONFIG_PCI_P2PDMA
+#ifdef CONFIG_NEED_SG_DMA_FLAGS
 	unsigned int    dma_flags;
 #endif
 };
@@ -249,12 +249,11 @@ static inline void sg_unmark_end(struct scatterlist *sg)
 }
 
 /*
- * CONFGI_PCI_P2PDMA depends on CONFIG_64BIT which means there is 4 bytes
- * in struct scatterlist (assuming also CONFIG_NEED_SG_DMA_LENGTH is set).
- * Use this padding for DMA flags bits to indicate when a specific
- * dma address is a bus address.
+ * One 64-bit architectures there is a 4-byte padding in struct scatterlist
+ * (assuming also CONFIG_NEED_SG_DMA_LENGTH is set). Use this padding for DMA
+ * flags bits to indicate when a specific dma address is a bus address.
  */
-#ifdef CONFIG_PCI_P2PDMA
+#ifdef CONFIG_NEED_SG_DMA_FLAGS
 
 #define SG_DMA_BUS_ADDRESS (1 << 0)
 
@@ -312,7 +311,7 @@ static inline void sg_dma_unmark_bus_address(struct scatterlist *sg)
 {
 }
 
-#endif
+#endif	/* CONFIG_NEED_SG_DMA_FLAGS */
 
 /**
  * sg_phys - Return physical address of an sg entry
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index 6677d0e64d27..acc6f231259c 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -24,6 +24,9 @@ config DMA_OPS_BYPASS
 config ARCH_HAS_DMA_MAP_DIRECT
 	bool
 
+config NEED_SG_DMA_FLAGS
+	bool
+
 config NEED_SG_DMA_LENGTH
 	bool