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SubjectRe: [PATCH v3 03/11] iio: Add channel for Position Relative
On Tue, 10 Apr 2018 11:57:49 +0300
Eugen Hristev <eugen.hristev@microchip.com> wrote:

> Add new channel type for relative position on a pad.
>
> These type of analog sensor offers the position of a pen
> on a touchpad, and is represented as a voltage, which can be
> converted to a position on X and Y axis on the pad.
> The channel will hand the relative position on the pad in both directions.
>
> The channel can then be consumed by a touchscreen driver or
> read as-is for a raw indication of the touchpen on a touchpad.
>
> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> ---
> Changes in v2:
> - modified channel name to relative position as suggested.
> - modified kernel version to 4.18 (presumable)
>
> Documentation/ABI/testing/sysfs-bus-iio | 12 ++++++++++++
> drivers/iio/industrialio-core.c | 1 +
> include/uapi/linux/iio/types.h | 1 +
> tools/iio/iio_event_monitor.c | 2 ++
> 4 files changed, 16 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> index 6a5f34b..42a9287 100644
> --- a/Documentation/ABI/testing/sysfs-bus-iio
> +++ b/Documentation/ABI/testing/sysfs-bus-iio
> @@ -190,6 +190,18 @@ Description:
> but should match other such assignments on device).
> Units after application of scale and offset are m/s^2.
>
> +What: /sys/bus/iio/devices/iio:deviceX/in_positionrelative_x_raw
> +What: /sys/bus/iio/devices/iio:deviceX/in_positionrelative_y_raw
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Relative position in direction x or y on a pad (may be
> + arbitrarily assigned but should match other such assignments on
> + device).
> + Units after application of scale and offset are milli percents
> + from the pad's size in both directions. Should be calibrated by
> + the consumer.
I know the milli percent comes form the humidity equivalent, but I wonder
if we are right to follow that. 10^-5 is a pretty random base unit (though
I got argued into it being a standard choice for humidity sensors IIRC...

What do people think? We could go with 1 for full range or just percent perhaps?

I'm not that fussed about staying consistent with humidity - we are unlikely
to end up with sensors doing both anytime soon so there shouldn't be
any confusion...

Jonathan
> +
> What: /sys/bus/iio/devices/iio:deviceX/in_anglvel_x_raw
> What: /sys/bus/iio/devices/iio:deviceX/in_anglvel_y_raw
> What: /sys/bus/iio/devices/iio:deviceX/in_anglvel_z_raw
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 19bdf3d..14bf3d24 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -85,6 +85,7 @@ static const char * const iio_chan_type_name_spec[] = {
> [IIO_COUNT] = "count",
> [IIO_INDEX] = "index",
> [IIO_GRAVITY] = "gravity",
> + [IIO_POSITIONRELATIVE] = "positionrelative",
> };
>
> static const char * const iio_modifier_names[] = {
> diff --git a/include/uapi/linux/iio/types.h b/include/uapi/linux/iio/types.h
> index 4213cdf..033c7d2 100644
> --- a/include/uapi/linux/iio/types.h
> +++ b/include/uapi/linux/iio/types.h
> @@ -44,6 +44,7 @@ enum iio_chan_type {
> IIO_COUNT,
> IIO_INDEX,
> IIO_GRAVITY,
> + IIO_POSITIONRELATIVE,
> };
>
> enum iio_modifier {
> diff --git a/tools/iio/iio_event_monitor.c b/tools/iio/iio_event_monitor.c
> index b61245e..148f69d 100644
> --- a/tools/iio/iio_event_monitor.c
> +++ b/tools/iio/iio_event_monitor.c
> @@ -58,6 +58,7 @@ static const char * const iio_chan_type_name_spec[] = {
> [IIO_PH] = "ph",
> [IIO_UVINDEX] = "uvindex",
> [IIO_GRAVITY] = "gravity",
> + [IIO_POSITIONRELATIVE] = "positionrelative",
> };
>
> static const char * const iio_ev_type_text[] = {
> @@ -151,6 +152,7 @@ static bool event_is_known(struct iio_event_data *event)
> case IIO_PH:
> case IIO_UVINDEX:
> case IIO_GRAVITY:
> + case IIO_POSITIONRELATIVE:
> break;
> default:
> return false;

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