Re: [PATCH 7/9] Input: n64joy - Fix DMA buffer alignment.

On Sun, Nov 27, 2022 at 06:48:44PM +0200, Lauri Kasanen wrote:

On Sun, 27 Nov 2022 14:41:14 +0000
Jonathan Cameron [off-list ref] wrote:

quoted

From: Jonathan Cameron <Jonathan.Cameron@huawei.com>

The use of ____cacheline_aligned to ensure a buffer is DMA safe only
enforces the start of the buffer alignment. In this case, sufficient
alignment is already ensured by the use of kzalloc().
____cacheline_aligned does not ensure that no other members of the
structure are placed in the same cacheline after the end of the
buffer marked.  Thus to ensure a DMA safe buffer it must be at the end
of the structure.

This move is unnecessary, because the cacheline is 16 bytes and the
buffer is 64 bytes.

I think it is still worth moving it or alternatively adding a comment
why we believe the following member will not be sharing cacheline with
the buffer.

Thanks.

-- 
Dmitry