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

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  Re: [PATCH v5 08/10] spi: expose master transfer size limitation. Mark Brown <broonie@kernel.org> - 2015-12-01 21:00 +0100
    Re: [PATCH v5 08/10] spi: expose master transfer size limitation. Heiner Kallweit <hkallweit1@gmail.com> - 2015-12-01 22:10 +0100
      Re: [PATCH v5 08/10] spi: expose master transfer size limitation. Mark Brown <broonie@kernel.org> - 2015-12-01 22:40 +0100
    Re: [PATCH v5 08/10] spi: expose master transfer size limitation. Michal Suchanek <hramrach@gmail.com> - 2015-12-02 11:00 +0100

#1281164 — Re: [PATCH v5 08/10] spi: expose master transfer size limitation.

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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?

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#1281215

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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#1281231

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On Tue, Dec 01, 2015 at 10:07:55PM +0100, Heiner Kallweit wrote:

> Sure .. Just one inquiry:
> When you say "the naming here" you refer to Michal's or my version?

Michael's (transfer).

> 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.

OK.

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#1281567

On 1 December 2015 at 20:58, Mark Brown <broonie@kernel.org> wrote:
> 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?

Sorry, missed there is a patch because it shows in the middle of the
discussion for me.

I don't really care which one it is so long as I can get the last
patch in this series based on it.

Thanks

Michal
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