linux-kernel - Re: [PATCH v2 6/7] iio: inv_mpu6050: Reformat sample for active scan mask

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Message-ID: <4EB54DBB-A77A-4BC5-8960-5CE9EB1B5DF2@kernel.org>
Date:	Mon, 30 May 2016 22:42:30 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Crestez Dan Leonard <leonard.crestez@...el.com>,
	linux-iio@...r.kernel.org
CC:	linux-kernel@...r.kernel.org, Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald-Stadler <pmeerw@...erw.net>,
	Daniel Baluta <daniel.baluta@...el.com>,
	Ge Gao <ggao@...ensense.com>, Peter Rosin <peda@...ntia.se>,
	linux-i2c@...r.kernel.org, Wolfram Sang <wsa@...-dreams.de>,
	devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>
Subject: Re: [PATCH v2 6/7] iio: inv_mpu6050: Reformat sample for active scan mask



On 30 May 2016 14:44:41 BST, Crestez Dan Leonard <leonard.crestez@...el.com> wrote:
>On 05/29/2016 06:47 PM, Jonathan Cameron wrote:
>> On 18/05/16 16:00, Crestez Dan Leonard wrote:
>>> Right now it is possible to only enable some of the x/y/z channels,
>for
>>> example you can enable accel_z without x or y but if you actually do
>>> that what you get is actually only the x channel.
>>>
>>> Fix this by reformatting the hardware sample to only include the
>>> requested channels.
>> As it stands here there is no benefit in doing this over using the
>core
>> demux. In fact it's considerably less efficient (fair enough that you
>> are keeping it simple in the first instance).
>> The patch description should make that clear.
>
>Why is it less efficient? All it really does is a bunch of memcpy.

Not doing agglomeration of neighbouring copies (iirc) not git either set of code to
hand!

>
>> I'd definitely like to see simple extension of that option to handle
>> a callback to get the nearest scanmask that is possible (as an
>alternative
>> to the static scan_masks_available list.)
>> 
>> This only gets interesting if we are dealing with the unaligned case
>and for
>> these parts that only kicks in I think if the slave devices have say
>3 bytes in
>> their data type.  
>
>But I want to deal with the unaligned case because it's better than
>introducing odd validations on slave channels. If I added an extension
>to get the nearest scanmask I would have to remove it in PATCH 7.
Hmm I must have misread that. Though you were only supporting 16 bit channels
 for aux sensors.

Then for now can we give this a slightly less generic name. I am not happy
 enough that we want this in the core 'yet'. 
Easy to rename later if it makes sense.

Thanks

Jonathan 

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