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

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Date:	Tue, 1 Dec 2015 22:07:55 +0100
From:	Heiner Kallweit <hkallweit1@...il.com>
To:	Mark Brown <broonie@...nel.org>,
	Michal Suchanek <hramrach@...il.com>
Cc:	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.

Am 01.12.2015 um 20:58 schrieb Mark Brown:
> On Tue, Dec 01, 2015 at 04:51:06PM -0000, Michal Suchanek wrote:
>> On some SPI controllers it is not feasible to transfer arbitrary amount
>> of data at once.
>>
>> When the limit on transfer size is a few kilobytes at least it makes
>> sense to use the SPI hardware rather than reverting to gpio driver.
> 
>> +	/*
>> +	 * on some hardware transfer size may be constrained
>> +	 * the limit may depend on device transfer settings
>> +	 */
>> +	size_t (*max_transfer_size)(struct spi_device *spi);
> 
> Heiner submitted a *very* similar patch just now with a straight
> variable plus accessor instead of a function and using a name with _msg.
> I'm ambivalent on the implementation but prefer the naming here since
> that's more the limitation we're trying to express I think (some
> hardware does have limiations about multple transfers too).  Can the two
> of you come up with something that works for both of you?
> 
Sure .. Just one inquiry:
When you say "the naming here" you refer to Michal's or my version?

Actually I like in Michal's hook that it directly takes a struct spi_device.
This saves the caller one level of indirection as the caller usually will
deal with a spi_device and not a spi_master.

If you're fine with Michal's version then this is also fine with me,
especially as the functionality is the same.

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