tree d50736f63bd9692076d68c3f8748f1b6bf540a80
parent bef9c558841604116704e10b3d9ff3dbf4939423
author Albert Lee <albertcc@tw.ibm.com> 1117093782 -0400
committer Jeff Garzik <jgarzik@pobox.com> 1117093782 -0400

[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>