Re: [PATCH v2 resend 2/2] iio: documentation: Document accelerometer label use

From: Bastien Nocera <hadess@hadess.net>
To: Hans de Goede <hdegoede@redhat.com>,
	Marcel Holtmann <marcel@holtmann.org>,
	Johan Hedberg <johan.hedberg@gmail.com>,
	Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: linux-bluetooth@vger.kernel.org,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Mark Pearson <mpearson@lenovo.com>
Subject: Re: [PATCH v2 resend 2/2] iio: documentation: Document accelerometer label use
Date: Fri, 16 Apr 2021 13:21:47 +0200	[thread overview]
Message-ID: <b679332b2dcba0bca2a645946ca0edc387fbda25.camel@hadess.net> (raw)
In-Reply-To: <871895f8-b85e-e8b0-83f1-de91636ce572@redhat.com>

On Fri, 2021-04-16 at 13:05 +0200, Hans de Goede wrote:
> Hi,
> 
> On 4/16/21 12:56 PM, Bastien Nocera wrote:
> > On Mon, 2021-04-05 at 22:39 +0200, Hans de Goede wrote:
> > > Some 2-in-1 laptops / convertibles with 360° (yoga-style) hinges,
> > > have 2 accelerometers, 1 in their base and 1 in their display.
> > > 
> > > In many cases the kernel can detect the location of each
> > > accelerometer
> > > based on e.g. information from the ACPI tables.
> > > 
> > > It is important for userspace to know the location of the 2
> > > accelerometers.
> > > Rather then adding a new sysfs-attribute for this we can relay
> > > this
> > > information to userspace by using standardized label strings for
> > > this.
> > > This mirrors how this is done for proximity sensors.
> > > 
> > > This commit documents 2 new standardized label strings for this
> > > purpose:
> > > "accel-base"
> > > "accel-display"
> > 
> > If we have a combined proximity and accelerometer sensor (which
> > wouldn't be unheard off with sensor hubs being used), how are
> > multiple
> > labels, say "proximity-wifi" and "accel-base" documented?
> 
> Sensor hubs typically use one iio device per sensor, see e.g.
> how HID-sensors work. And if a device which does not use separate
> iio-devices per sensor shows up then the plan is to use per
> channel-labels which are already supported by iio.

OK.

> 
> Regards,
> 
> Hans
> 
> 
> 
> > > Note the "base" and "display" suffixes were chosen to match the
> > > values
> > > used for the systemd/udev hwdb.d/60-sensor.hwdb file's
> > > ACCEL_LOCATION
> > > property.
> > > 
> > > Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> > > Cc: Mark Pearson <mpearson@lenovo.com>
> > > Cc: Bastien Nocera <hadess@hadess.net>
> > > Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> > > ---
> > >  Documentation/ABI/testing/sysfs-bus-iio | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > > 
> > > diff --git a/Documentation/ABI/testing/sysfs-bus-iio
> > > b/Documentation/ABI/testing/sysfs-bus-iio
> > > index 7379e40d862d..b7529bca83f5 100644
> > > --- a/Documentation/ABI/testing/sysfs-bus-iio
> > > +++ b/Documentation/ABI/testing/sysfs-bus-iio
> > > @@ -72,6 +72,13 @@ Description:
> > >                 calculated by firmware from other sensor
> > > readings,
> > > rather then
> > >                 being a raw sensor reading.
> > >  
> > > +               For accelerometers used in 2-in-1s with 360°
> > > (yoga-
> > > style) hinges,
> > > +               which have an accelerometer in both their base
> > > and
> > > their display,
> > > +               the following standardized labels are used:
> > > +
> > > +               * "accel-base"
> > > +               * "accel-display"
> > > +
> > >  What:          /sys/bus/iio/devices/iio:deviceX/current_timestam
> > > p_cl
> > > ock
> > >  KernelVersion: 4.5
> > >  Contact:       linux-iio@vger.kernel.org
> > 
> > 
> 