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From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Lauri Kasanen <cand@gmx.com>
Cc: Jonathan Cameron <jic23@kernel.org>,
	linux-input@vger.kernel.org,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>
Subject: Re: [PATCH 7/9] Input: n64joy - Fix DMA buffer alignment.
Date: Mon, 28 Nov 2022 10:04:43 -0800	[thread overview]
Message-ID: <Y4T4O0wVd2EMWOJ9@google.com> (raw)
In-Reply-To: <20221127184844.f967054e30c47a3caa5090eb@gmx.com>

On Sun, Nov 27, 2022 at 06:48:44PM +0200, Lauri Kasanen wrote:
> On Sun, 27 Nov 2022 14:41:14 +0000
> Jonathan Cameron <jic23@kernel.org> wrote:
> 
> > 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

  parent reply	other threads:[~2022-11-28 18:20 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-27 14:41 [PATCH 0/9] Input: Fix insufficent DMA alignment Jonathan Cameron
2022-11-27 14:41 ` [PATCH 1/9] Input: psxpad - Fix padding for DMA safe buffers Jonathan Cameron
2022-11-27 14:41 ` [PATCH 2/9] Input: ad714x " Jonathan Cameron
2022-11-28  7:14   ` Hennerich, Michael
2022-11-27 14:41 ` [PATCH 3/9] Input: ad7887 " Jonathan Cameron
2022-11-28  7:14   ` Hennerich, Michael
2022-11-27 14:41 ` [PATCH 4/9] Input: ads7846 " Jonathan Cameron
2022-11-27 14:41 ` [PATCH 5/9] Input: cyttsp " Jonathan Cameron
2022-11-27 14:41 ` [PATCH 6/9] Input: surface3 " Jonathan Cameron
2022-11-27 16:26   ` Jonathan Cameron
2022-11-27 14:41 ` [PATCH 7/9] Input: n64joy - Fix DMA buffer alignment Jonathan Cameron
2022-11-27 16:48   ` Lauri Kasanen
2022-11-27 18:01     ` Jonathan Cameron
2022-11-28  6:49       ` Lauri Kasanen
2022-11-28 18:04     ` Dmitry Torokhov [this message]
2022-11-27 14:41 ` [PATCH 8/9] Input: atmel_captouch - Avoid suspect " Jonathan Cameron
2022-11-27 14:41 ` [PATCH 9/9] Input: elants - Fix " Jonathan Cameron
2022-11-28 18:16 ` [PATCH 0/9] Input: Fix insufficent DMA alignment Dmitry Torokhov
2022-11-29  9:18   ` Jonathan Cameron
2022-11-30  1:23     ` Dmitry Torokhov

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