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

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Date:	Mon, 30 May 2016 16:44:41 +0300
From:	Crestez Dan Leonard <leonard.crestez@...el.com>
To:	Jonathan Cameron <jic23@...nel.org>, 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 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.

> 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.

-- 
Regards,
Leonard