linux-kernel - Re: [PATCH 3/4] liss331d1: accelerometer driver

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Date:	Thu, 15 Apr 2010 11:47:40 +0200
From:	Éric Piel <eric.piel@...mplin-utc.net>
To:	Neil Brown <neilb@...e.de>
CC:	Daniel Mack <daniel@...aq.de>, Alan Cox <alan@...ux.intel.com>,
	linux-i2c@...r.kernel.org, khali@...ux-fr.org,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Samu Onkalo <samu.p.onkalo@...ia.com>
Subject: Re: [PATCH 3/4] liss331d1: accelerometer driver

On 15/04/10 01:05, Neil Brown wrote:
:
> 
> The Openmoko Freerunner has as lis302D which is an SPI version of a very
> similar device, so making the one driver work on that was well would be nice
> if possible.
Definitely!

> 
> The lis302d can detect threshold crossings and taps as well as simple
> orientation and I found it useful to include support for those in the driver
> as well.
> In particular:
>  1/ I allowed the 'data_rate' that was programmed to be any number (including 
>     fractions and 0) and the driver would report at that rate, using a timer
>     for rates below 50Hz.
>     When the app is only interested in long-term change, this can
>     significantly reduce the amount of data that has to be handled by
>     userspace.
Samu (from Nokia) has started to had such idea via the patch
lis3-setup-poll-interval-limits.patch which in now in the -mm tree. It
allows to specify the polling rate via the input interface
(/sys/devices/platform/lis3lv02d/input/input8/poll). But for now I don't
think the actual refresh rate is updated automatically, it would be a
nice addition.


> 
>  2/ I allowed a 'threshold' to be set so that changes bigger than that get
>     notified promptly even if that is faster than the requested data rate
It could be interesting too... but what interface are you using for the
userspace to specify this threshold? A sysfs file?

> 
>  3/ I allowed taps to be detected and reported as BTN_X BTN_Y and BTN_Z
>     input events.
This one should now be working with Samu's patch
lis3-interrupt-handlers-for-8bit-wakeup-and-click-events.patch also in
the -mm tree.

> 
> Would it be sensible to include that support in this driver?  The
> LIS331DL seem to have the same threshold and tap support.
So all in all, if you could have a look at what changes are necessary to
get the lis3lv02d driver work with your hardware, it would be great. (I
suspect it should be quite little.)

See you,
Eric
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