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From: Bastien Nocera <hadess@hadess.net>
To: Hans de Goede <hdegoede@redhat.com>, linux-iio@vger.kernel.org
Subject: Re: accelerometer orientation
Date: Mon, 12 Sep 2016 17:39:15 +0200	[thread overview]
Message-ID: <1473694755.6389.2.camel@hadess.net> (raw)
In-Reply-To: <0b744f22-55c0-da22-b27f-6092aab18365@redhat.com>

Hey,

On Mon, 2016-09-12 at 17:25 +0200, Hans de Goede wrote:
> Hi Bastien,
> 
> So as I guess you sorta know in my spare time I work on Linux
> (mainline) support for Allwinner SoC based ARM devices, including
> a whole lot of cheap Chinese tablets.
> 
> Recently I've begun looking into supporting the accelerometers
> on these devices and I'm making good progress on getting the
> kernel bits working using iio drivers (including a few new
> ones I've written recently).
> 
> Yesterday I realized there is a bit of a catch though, all
> these iio drivers report results assuming that the accelerometer
> is mounted on the top side of the PCB and with its X/Y
> coordination properly taken info account.
> 
> Unfortunately neither is necessarily true. Almost all
> tablet PCBS are mounted upside down (with an empty PCB
> backside against the lcd-panel. Meaning that the Z axis
> reads -1G when the tablet is lying on its back instead
> of the expected +1G and some need X/Y axis swapping and/or
> inversion too.
> 
> So there are 3 problems here:
> 
> 1) Where do we store the orientation of the chip
> 
<snip>
> 2) Where do we correct the readings for the orientation
<snip>
> 3) Currently implementing orientation support in an iio driver
> requires copy and pasting quite a bit of boiler plate, so
> a question to the linux-iio list, has anyone though of an
> easier way to do this. I really just want to be able to
> pass say a single flag to iio_device_register and then
> have the iio-core automatically call of_iio_read_mount_matrix()
> and add mount_matrix ext_info.

All good ideas, but we need a way to do this for devices without DT
(meaning all of the x86 tablets).

Perhaps iio-sensor-proxy could read from udev instead, and udev either
pull from DT when available, or apply from its own rules?

Cheers

  reply	other threads:[~2016-09-12 15:39 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-12 15:25 accelerometer orientation Hans de Goede
2016-09-12 15:39 ` Bastien Nocera [this message]
2016-09-12 16:15   ` Hans de Goede
2016-09-18 19:32     ` Jonathan Cameron
2016-09-19 14:14       ` Hans de Goede
2016-09-25  8:31         ` Jonathan Cameron

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