linux-kernel - Re: [PATCH 1/1] spi: imx: fix issue when tx_buf or rx

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Date:   Fri, 19 May 2017 17:56:11 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Chris Ruehl <chris.ruehl@...ys.com.hk>,
        Jiada Wang <jiada_wang@...tor.com>,
        linux-spi <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        leonard.crestez@....com
Subject: Re: [PATCH 1/1] spi: imx: fix issue when tx_buf or rx_buf is NULL

On Fri, May 19, 2017 at 04:15:01PM +0300, Andy Shevchenko wrote:
> On Fri, May 19, 2017 at 3:45 PM, Chris Ruehl <chris.ruehl@...ys.com.hk> wrote:

> > But I think we missing something here. We return from a void function()
> > so the error keeps hidden. The root cause is calling this functions with a
> > NULL pointer. See if you can fix this by find the caller and check if the
> > parameter hand over are valid.

> AFAIU some SPI controllers can have half-duplex protocol, in which the
> second buffer might be absent.

Yes, it's not only perfectly valid but actually the common case for only
one direction of data to be meaningful in SPI so the majority of
controllers don't require data to be transferred in both directions, it
would just add bus overhead.

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