linux-kernel - Re: [RFC PATCH 2/2 -mm] RapidIO: TSI721 Add DMA Engine support

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Message-Id: <20111004185718.a5806a7e.akpm00@gmail.com>
Date:	Tue, 4 Oct 2011 18:57:18 -0700
From:	Andrew Morton <akpm00@...il.com>
To:	"Bounine, Alexandre" <Alexandre.Bounine@....com>
Cc:	Vinod Koul <vinod.koul@...el.com>, <linux-kernel@...r.kernel.org>,
	<linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [RFC PATCH 2/2 -mm] RapidIO: TSI721 Add DMA Engine support

On Tue, 4 Oct 2011 18:38:09 -0700 "Bounine, Alexandre" <Alexandre.Bounine@....com> wrote:

> > No, it can be used all over the place: drivers/net/irda/w83977af_ir.c,
> > drivers/scsi/bnx2fc/bnx2fc_tgt.c,
> > drivers/net/wireless/rt2x00/rt2x00pci.c,
> > drivers/crypto/amcc/crypto4xx_core.c and many nmore.
> 
> In this case I will happily use dma_zalloc_coherent() as soon as
> it is available

geeze, which of us is more lazy?

Here we go...


From: Andrew Morton <akpm@...ux-foundation.org>
Subject: include/linux/dma-mapping.h: add dma_zalloc_coherent()

Lots of driver code does a dma_alloc_coherent() and then zeroes out the
memory with a memset.  Make it easy for them.

Cc: Alexandre Bounine <alexandre.bounine@....com>
From: Andrew Morton <akpm@...ux-foundation.org>
Subject: include-linux-dma-mappingh-add-dma_zalloc_coherent
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 Documentation/DMA-API.txt   |    7 +++++++
 include/linux/dma-mapping.h |   10 ++++++++++
 2 files changed, 17 insertions(+)

diff -puN include/linux/dma-mapping.h~include-linux-dma-mappingh-add-dma_zalloc_coherent include/linux/dma-mapping.h
--- a/include/linux/dma-mapping.h~include-linux-dma-mappingh-add-dma_zalloc_coherent
+++ a/include/linux/dma-mapping.h
@@ -1,6 +1,7 @@
 #ifndef _LINUX_DMA_MAPPING_H
 #define _LINUX_DMA_MAPPING_H
 
+#include <linux/string.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/dma-attrs.h>
@@ -117,6 +118,15 @@ static inline int dma_set_seg_boundary(s
 		return -EIO;
 }
 
+static inline void *dma_zalloc_coherent(struct device *dev, size_t size,
+					dma_addr_t *dma_handle, gfp_t flag)
+{
+	void *ret = dma_alloc_coherent(dev, size, dma_handle, flag);
+	if (ret)
+		memset(ret, 0, size);
+	return ret;
+}
+
 #ifdef CONFIG_HAS_DMA
 static inline int dma_get_cache_alignment(void)
 {
diff -puN Documentation/DMA-API.txt~include-linux-dma-mappingh-add-dma_zalloc_coherent Documentation/DMA-API.txt
--- a/Documentation/DMA-API.txt~include-linux-dma-mappingh-add-dma_zalloc_coherent
+++ a/Documentation/DMA-API.txt
@@ -50,6 +50,13 @@ specify the GFP_ flags (see kmalloc) for
 implementation may choose to ignore flags that affect the location of
 the returned memory, like GFP_DMA).
 
+void *
+dma_zalloc_coherent(struct device *dev, size_t size,
+			     dma_addr_t *dma_handle, gfp_t flag)
+
+Wraps dma_alloc_coherent() and also zeroes the returned memory if the
+allocation attempt succeeded.
+
 void
 dma_free_coherent(struct device *dev, size_t size, void *cpu_addr,
 			   dma_addr_t dma_handle)
_

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