linux-kernel - Re: [PATCH 2/3] MTD: spi-nor: check for short writes in spi_nor

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Message-ID: <20150522093714.GS21577@sirena.org.uk>
Date:	Fri, 22 May 2015 10:37:14 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	Michal Suchanek <hramrach@...il.com>,
	linux-sunxi <linux-sunxi@...glegroups.com>,
	Marek Vasut <marex@...x.de>,
	Rafał Miłecki <zajec5@...il.com>,
	Alison Chaiken <alison_chaiken@...tor.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Bean Huo 霍斌斌 (beanhuo) 
	<beanhuo@...ron.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mtd@...ts.infradead.org,
	linux-spi <linux-spi@...r.kernel.org>
Subject: Re: [PATCH 2/3] MTD: spi-nor: check for short writes in
 spi_nor_write.

On Fri, May 22, 2015 at 12:25:05AM -0700, Brian Norris wrote:
> On Fri, May 22, 2015 at 12:17:27AM -0700, Brian Norris wrote:

> > Admittedly, as he's using an out-of-tree driver, I'm not
> > sure I know exactly what failure modes he is hitting yet.

> Sorry, I realized I misread here. He's using spi-sunxi. Given that...

> ... is this code even valid?

> static int sun6i_spi_transfer_one(struct spi_master *master,
>                                   struct spi_device *spi,
>                                   struct spi_transfer *tfr)
> {
> ...
> 	/* We don't support transfer larger than the FIFO */
> 	if (tfr->len > SUN6I_FIFO_DEPTH)
> 		return -EINVAL;

> Seems like it should be looping over the transfer in multiple chunks
> instead.

Well, it's not ideal.  Like I say I think that logic probably belongs in
the core rather than individual drivers then we minimise the problems,
if I remember correctly there was the suggestion that the DMA code was
going to follow soon and be used for larger transfers when the original
driver was merged.

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