linux-kernel - Re: [PATCH] atmel_spi: support zero length transfer (resend)

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Date:	Sat, 29 Mar 2008 17:56:51 +0100
From:	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
To:	Atsushi Nemoto <anemo@....ocn.ne.jp>
Cc:	David Brownell <david-b@...bell.net>,
	spi-devel-general@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	marc.pignat@...s.ch, nforrester@...i.edu
Subject: Re: [PATCH] atmel_spi: support zero length transfer (resend)

Atsushi Nemoto <anemo@....ocn.ne.jp> wrote:
> A spi transfer with zero length is not invalid.  For example, such
> transfer (len == 0 && delay_usecs != 0) can be used to achieve delay
> before first CLK edge after chipselect assertion.
> 
> Signed-off-by: Atsushi Nemoto <anemo@....ocn.ne.jp>
> ---
> Though some discussion about zero length transfer were raised by this
> patch last time, I think there were no explicit objection to this
> patch itself.

Well, the patch doesn't seem to do any harm, but I can't see much of a
point to it either if zero-length transfers aren't going to be
allowed...

Also, if the length is zero, the driver will end up doing a memset with
length zero at some point. Is that allowed?

Haavard
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