linux-kernel - Re: [PATCH v5 08/10] spi: expose master transfer size limitation.

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Message-ID: <20151207201804.GP5727@sirena.org.uk>
Date:	Mon, 7 Dec 2015 20:18:04 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Martin Sperl <martin@...rl.org>
Cc:	Michal Suchanek <hramrach@...il.com>,
	Heiner Kallweit <hkallweit1@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	Han Xu <han.xu@...escale.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Javier Martinez Canillas <javier@....samsung.com>,
	Stephen Warren <swarren@...dia.com>,
	"Andrew F. Davis" <afd@...com>, Marek Vasut <marex@...x.de>,
	Rafał Miłecki <zajec5@...il.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Gabor Juhos <juhosg@...nwrt.org>,
	Bean Huo 霍斌斌 <beanhuo@...ron.com>,
	Furquan Shaikh <furquan@...gle.com>,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-spi@...r.kernel.org
Subject: Re: [PATCH v5 08/10] spi: expose master transfer size limitation.

On Fri, Dec 04, 2015 at 03:30:50PM +0100, Martin Sperl wrote:
> > On 02.12.2015, at 00:12, Mark Brown <broonie@...nel.org> wrote:

> > Can we change this to return SIZE_MAX instead (ie, the maximum value for
> > a size_t)?  That way callers don't need to worry if there is a limit, if
> > they want to handle it they can just unconditionally assume that a limit
> > will be provided.

> As I just came across: spi_master.max_dma_len, so I wonder how this 
> value would differ from the proposed spi_master.max_transfer_size
> on specific HW?

> For all practical purposes I would assume both are identical.

Yeah, we should probably just remove the DMA specific one in time though
it may be useful for some devices with built in DMA engines if they're
oddly limited I'm not sure how practical their DMA would be if it
differed from the overall transfer length.

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