Re: [PATCH 36/56] microblaze_v2: dma support

Michal Simek
2008-05-06T09:53:09Z

Hi,
> On Tue, 6 May 2008, Michal Simek wrote:
>>> On Mon, 5 May 2008, John Williams wrote:
>>>>> +++ b/include/asm-microblaze/scatterlist.h
>>>>> @@ -0,0 +1,21 @@
>>>>> +/*
>>>>> + * include/asm-microblaze/scatterlist.h
>>>>> + *
>>>>> + * This file is subject to the terms and conditions of the GNU General Public
>>>>> + * License. See the file "COPYING" in the main directory of this archive
>>>>> + * for more details.
>>>>> + *
>>>>> + * Copyright (C) 2006 Atmark Techno, Inc.
>>>>> + */
>>>>> +
>>>>> +#ifndef _ASM_MICROBLAZE_SCATTERLIST_H
>>>>> +#define _ASM_MICROBLAZE_SCATTERLIST_H
>>>>> +
>>>>> +struct scatterlist {
>>>>> + unsigned long page_link;
>>>>> + unsigned int offset;
>>>>> + dma_addr_t dma_address;
>>>>> + unsigned int length;
>>>>> +};
>>>>> +
>>>>> +#endif /* _ASM_MICROBLAZE_SCATTERLIST_H */
>>>> Is this worthy of promotion to asm-generic/scatterlist.h?
>>> after moving dma_address one position up in the structure, as dma_addr_t may be
>>> 64-bit?
>> dma_addr_t is defined in types.h. If your arch want to use 64bit addr, you can
>> define it in types.h.
>
> Sorry for not making myself clear: If unsigned long and dma_addr_t are 64-bit,
> there may be a hole in between offset and dma_address, due to alignment
> restrictions. So it's better to move dma_address up.
>
> As dma_addr_t may be 64-bit even on 32-bit architectures, it may be best
> to move it even to the start of the structure.

yes, only move length is enough.

struct scatterlist {
unsigned long page_link;
unsigned int offset;
unsigned int length;
dma_addr_t dma_address;
};

Michal