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Date: Thu, 03 Jul 2014 19:58:52 +0200
From: Lars-Peter Clausen <lars@metafoo.de>
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To: Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
CC: Bastien Nocera <hadess@hadess.net>,
	Jonathan Cameron <jic23@kernel.org>,
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	Reyad Attiyat <reyad.attiyat@gmail.com>,
	linux-iio@vger.kernel.org,
	Benjamin Tissoires <benjamin.tissoires@redhat.com>
Subject: Re: User-space API for accelerometer(s)?
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On 07/03/2014 07:51 PM, Jonathan Cameron wrote:
> On 01/07/14 13:10, Bastien Nocera wrote:
>> Hey again Jonathan,
>>
>> On Sat, 2014-06-21 at 13:01 +0100, Jonathan Cameron wrote:
>> <snip>
>>> Just to throw it in there.  There is an out of tree bridge driver from
>>> IIO to input.  It's only out of tree because I haven't had a chance to
>>> tidy it up (anyone else is welcome to take this on if they like!)
>>> Google for iio_input.c to find it.
>>>
>>> The intent of that was to allow general accelerometer drivers and similar
>>> in IIO to work in conjunction with iio-input to provide input style interfaces.
>>> This came about after previous debates on where the 'right' place for
>>> accelerometers was in the kernel. I believe that at least in principle,
>>> Dmitry was happy with this concept.
>>
>> After updating forward-porting the driver so that it runs on a more
>> recent version of the kernel, I tried to get it running.
>>
>> I'm guessing that you expected the iio_input driver to be instantiated
>> by a board specific file. Is there any way to have it generically try
>> out all the IIO devices, similarly to pci_register_driver()? Or should I
>> do that in the hid-sensor-accel driver?
> At the moment we only have support to instantiate it via such a board specific
> file. We probably want to be a little careful about how to add more generic
> means for creating such bindings..
>
> Simply generically trying all IIO drivers isn't the way to go as there is
> no obvious way of deciding what it makes sense to bind to on a given machine.
>
> Perhaps something closer to the way you can instantiate i2c devices from
> userspace, or perhaps we need to consider something else such as configfs for
> creating such bindings... (cc'd Lars for comments on whether that makes sense...)

Yes, configfs is what came to my mind after reading the first few lines of 
Bastien's mail. Exposing a IIO device as something other than a IIO device is a 
policy decision. And policy decisions should preferably be made by userspace. 
But yea, we have to be careful with the ABI.

- Lars