From: Albert Lee <albertcc@tw.ibm.com>
Date: Thu, 26 May 2005 07:49:42 +0000 (-0400)
Subject: [PATCH] libata: Fix zero sg_dma_len() on 64-bit platform
X-Git-Tag: v2.6.12-rc6~146^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=32529e0128923e42126b5d14e444c18295a452ba;p=pandora-kernel.git

[PATCH] libata: Fix zero sg_dma_len() on 64-bit platform

When testing ATAPI PIO data transfer on the ppc64 platform,  __atapi_pio_bytes() got zero when
sg_dma_len() is used. I checked the <asm-ppc64/scatterlish.h>, the struct scatterlist is defined as:

struct scatterlist {
	struct page *page;
	unsigned int offset;
	unsigned int length;

	/* For TCE support */
	u32 dma_address;
	u32 dma_length;
};

#define sg_dma_address(sg)	((sg)->dma_address)
#define sg_dma_len(sg)		((sg)->dma_length)

So, if the scatterlist is not DMA mapped, sg_dma_len() will return zero on ppc64.
The same problem should occur on the x86-64 platform.
On the i386 platform, sg_dma_len() returns sg->length, that's why the problem does not occur on an i386.

Changes:
- Use sg->length if the scatterlist is not DMA mapped (yet).

Signed-off-by: Albert Lee <albertcc@tw.ibm.com>
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