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* dma-mapping: use bit macros
@ 2019-11-29 20:27 Heiner Kallweit
  2019-11-30  8:18 ` Christoph Hellwig
  0 siblings, 1 reply; 2+ messages in thread
From: Heiner Kallweit @ 2019-11-29 20:27 UTC (permalink / raw)
  To: Christoph Hellwig, Marek Szyprowski, Robin Murphy
  Cc: open list:AMD IOMMU \(AMD-VI\), Linux Kernel Mailing List

Not necessarily a big leap for mankind, but using bit macros makes
the code better readable, especially the definition of DMA_BIT_MASK
is more intuitive.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 include/linux/dma-mapping.h | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index a4930310d..a39a6a8d5 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -2,6 +2,7 @@
 #ifndef _LINUX_DMA_MAPPING_H
 #define _LINUX_DMA_MAPPING_H
 
+#include <linux/bits.h>
 #include <linux/sizes.h>
 #include <linux/string.h>
 #include <linux/device.h>
@@ -21,51 +22,51 @@
  * DMA_ATTR_WEAK_ORDERING: Specifies that reads and writes to the mapping
  * may be weakly ordered, that is that reads and writes may pass each other.
  */
-#define DMA_ATTR_WEAK_ORDERING		(1UL << 1)
+#define DMA_ATTR_WEAK_ORDERING		BIT(1)
 /*
  * DMA_ATTR_WRITE_COMBINE: Specifies that writes to the mapping may be
  * buffered to improve performance.
  */
-#define DMA_ATTR_WRITE_COMBINE		(1UL << 2)
+#define DMA_ATTR_WRITE_COMBINE		BIT(2)
 /*
  * DMA_ATTR_NON_CONSISTENT: Lets the platform to choose to return either
  * consistent or non-consistent memory as it sees fit.
  */
-#define DMA_ATTR_NON_CONSISTENT		(1UL << 3)
+#define DMA_ATTR_NON_CONSISTENT		BIT(3)
 /*
  * DMA_ATTR_NO_KERNEL_MAPPING: Lets the platform to avoid creating a kernel
  * virtual mapping for the allocated buffer.
  */
-#define DMA_ATTR_NO_KERNEL_MAPPING	(1UL << 4)
+#define DMA_ATTR_NO_KERNEL_MAPPING	BIT(4)
 /*
  * DMA_ATTR_SKIP_CPU_SYNC: Allows platform code to skip synchronization of
  * the CPU cache for the given buffer assuming that it has been already
  * transferred to 'device' domain.
  */
-#define DMA_ATTR_SKIP_CPU_SYNC		(1UL << 5)
+#define DMA_ATTR_SKIP_CPU_SYNC		BIT(5)
 /*
  * DMA_ATTR_FORCE_CONTIGUOUS: Forces contiguous allocation of the buffer
  * in physical memory.
  */
-#define DMA_ATTR_FORCE_CONTIGUOUS	(1UL << 6)
+#define DMA_ATTR_FORCE_CONTIGUOUS	BIT(6)
 /*
  * DMA_ATTR_ALLOC_SINGLE_PAGES: This is a hint to the DMA-mapping subsystem
  * that it's probably not worth the time to try to allocate memory to in a way
  * that gives better TLB efficiency.
  */
-#define DMA_ATTR_ALLOC_SINGLE_PAGES	(1UL << 7)
+#define DMA_ATTR_ALLOC_SINGLE_PAGES	BIT(7)
 /*
  * DMA_ATTR_NO_WARN: This tells the DMA-mapping subsystem to suppress
  * allocation failure reports (similarly to __GFP_NOWARN).
  */
-#define DMA_ATTR_NO_WARN	(1UL << 8)
+#define DMA_ATTR_NO_WARN		BIT(8)
 
 /*
  * DMA_ATTR_PRIVILEGED: used to indicate that the buffer is fully
  * accessible at an elevated privilege level (and ideally inaccessible or
  * at least read-only at lesser-privileged levels).
  */
-#define DMA_ATTR_PRIVILEGED		(1UL << 9)
+#define DMA_ATTR_PRIVILEGED		BIT(9)
 
 /*
  * A dma_addr_t can hold any valid DMA or bus address for the platform.
@@ -136,7 +137,7 @@ struct dma_map_ops {
 extern const struct dma_map_ops dma_virt_ops;
 extern const struct dma_map_ops dma_dummy_ops;
 
-#define DMA_BIT_MASK(n)	(((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
+#define DMA_BIT_MASK(n)	GENMASK_ULL(n - 1, 0)
 
 #define DMA_MASK_NONE	0x0ULL
 
-- 
2.24.0

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^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: dma-mapping: use bit macros
  2019-11-29 20:27 dma-mapping: use bit macros Heiner Kallweit
@ 2019-11-30  8:18 ` Christoph Hellwig
  0 siblings, 0 replies; 2+ messages in thread
From: Christoph Hellwig @ 2019-11-30  8:18 UTC (permalink / raw)
  To: Heiner Kallweit
  Cc: Linux Kernel Mailing List, open list:AMD IOMMU \(AMD-VI\),
	Robin Murphy, Christoph Hellwig

On Fri, Nov 29, 2019 at 09:27:26PM +0100, Heiner Kallweit wrote:
> Not necessarily a big leap for mankind, but using bit macros makes
> the code better readable, especially the definition of DMA_BIT_MASK
> is more intuitive.

NAK, I'm against this pointless obsfucation.
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iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

^ permalink raw reply	[flat|nested] 2+ messages in thread

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