linux-kernel - Re: [PATCH v2] spi: core: Validate lenght of the transfers in message

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Message-ID: <20140218000938.GE2669@sirena.org.uk>
Date:	Tue, 18 Feb 2014 09:09:38 +0900
From:	Mark Brown <broonie@...nel.org>
To:	Gerhard Sittig <gsi@...x.de>
Cc:	"Ivan T. Ivanov" <iivanov@...sol.com>, linux-spi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] spi: core: Validate lenght of the transfers in message

On Sun, Feb 16, 2014 at 03:25:12PM +0100, Gerhard Sittig wrote:
> On Sat, Feb 15, 2014 at 08:09 +0200, Ivan T. Ivanov wrote:

> - the total length of the SPI transfer cannot be empty (which I'd
>   consider an optimization, not a violation, and may need a
>   separate discussion)

We probably want to allow that for people doing fun stuff with cs_change
though I'm not convinced anything doing that is actually a good idea.

> - the total length of the SPI transfer must be such that each
>   "word" must be provided within a full 1/2/4 byte entity, with
>   padding bits if the bits-per-word is "odd"

> Is this a misunderstanding on my side?  A terminology thing?  To
> me, the "SPI transfer" is the total payload and may have any
> arbitrary length.  What you check for is a constraint on the
> transfer's length derived from or based on the "word length"
> ('word' in SPI context).

> So the code may be appropriate, yet the description may need an
> update, to not have the next person ask the same questions again.

It seems fairly clear to me - if we're transferring 16 bit words we need
the transfer to me a multiple of 16 bits and so on?  The requirement for
padding is unclear I have to say.

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