Subject: Re: [PATCH v5 08/10] spi: expose master transfer size limitation.
To: Mark Brown <broonie@kernel.org>, Michal Suchanek <hramrach@gmail.com>
References: <cover.1448988089.git.hramrach@gmail.com>
 <8c34c7790244489c2ce0072c72bd9bc7c4cdb965.1448988089.git.hramrach@gmail.com>
 <20151201195816.GS1929@sirena.org.uk>
Cc: David Woodhouse <dwmw2@infradead.org>,
        Brian Norris <computersforpeace@gmail.com>,
        Han Xu <han.xu@freescale.com>,
        Boris Brezillon <boris.brezillon@free-electrons.com>,
        Javier Martinez Canillas <javier@osg.samsung.com>,
        Stephen Warren <swarren@nvidia.com>, "Andrew F. Davis" <afd@ti.com>,
        Marek Vasut <marex@denx.de>,
        =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= <zajec5@gmail.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Gabor Juhos <juhosg@openwrt.org>,
        =?UTF-8?B?QmVhbiBIdW8g6ZyN5paM5paM?= <beanhuo@micron.com>,
        Furquan Shaikh <furquan@google.com>, linux-mtd@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org
From: Heiner Kallweit <hkallweit1@gmail.com>
Message-ID: <565E0C2B.4070504@gmail.com>
Date: Tue, 1 Dec 2015 22:07:55 +0100
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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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