Re: [PATCH v4 1/2] iio: Implement counter channel type and info constants

From: Jonathan Cameron
Date: Tue Sep 27 2016 - 15:31:38 EST


On 27/09/16 19:30, William Breathitt Gray wrote:
> On Sat, Sep 24, 2016 at 06:03:21PM +0100, Jonathan Cameron wrote:
>> On 21/09/16 21:15, William Breathitt Gray wrote:
>>> Quadrature encoders, such as rotary encoders and linear encoders, are
>>> devices which are capable of encoding the relative position and
>>> direction of motion of a shaft. This patch introduces several IIO
>>> constants for supporting quadrature encoder counter devices.
>>>
>>> IIO_COUNT: Current count (main data provided by the counter device)
>>> IIO_INDEX: Counter device index value
>>> IIO_CHAN_INFO_PRESET: Counter preset value
>>>
>>> Signed-off-by: William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
>>> ---
>>> Documentation/ABI/testing/sysfs-bus-iio | 28 ++++++++++++++++++++++++++++
>>> drivers/iio/industrialio-core.c | 3 +++
>>> include/linux/iio/iio.h | 1 +
>>> include/uapi/linux/iio/types.h | 2 ++
>>> 4 files changed, 34 insertions(+)
>>>
>>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
>>> index fee35c0..be66a41 100644
>>> --- a/Documentation/ABI/testing/sysfs-bus-iio
>>> +++ b/Documentation/ABI/testing/sysfs-bus-iio
>>> @@ -1579,3 +1579,31 @@ Contact: linux-iio@xxxxxxxxxxxxxxx
>>> Description:
>>> Raw (unscaled no offset etc.) electric conductivity reading that
>>> can be processed to siemens per meter.
>>> +
>>> +What: /sys/bus/iio/devices/iio:deviceX/in_countY_raw
>>> +KernelVersion: 4.9
>>> +Contact: linux-iio@xxxxxxxxxxxxxxx
>>> +Description:
>>> + Raw counter device counts from channel Y. For quadrature
>>> + counters, division by an available [Y]_scale results in the
>>> + counts of a single quadrature signal phase from channel Y.
>> Division? Needs to be multiplication to be consistent with the other
>> interfaces.
>
> That makes sense. What I'll do is refactor scale to accept the values 1,
> 0.5, and 0.25 to select the respective x1, x2, and x4 quadrature modes.
>
> The counter device will count full-phase edges on quadrature x1 mode,
> half-phase edges on quadrature x2 mode (twice as many counts as x1), and
> quarter-phase edges on quadrature x4 mode (twice as many counts as x2).
> One of the benefits of the x2 and x4 quadrature modes is increased
> position fidelity, so exposing scale as a fraction will allow it to be
> multipled to raw counts without sacrificing the precision benefit of the
> x2 and x4 quadrature modes.
>
Spot on.

Jonathan
> William Breathitt Gray
>
>>> +
>>> +What: /sys/bus/iio/devices/iio:deviceX/in_countY_scale
>>> +KernelVersion: 4.9
>>> +Contact: linux-iio@xxxxxxxxxxxxxxx
>>> +Description:
>>> + If a scale value is available for channel Y, it is provided by
>>> + this attribute.
>> Can just add the What line to the big block of _scale attributes already
>> listed. Generic text should cover it fine.
>>> +
>>> +What: /sys/bus/iio/devices/iio:deviceX/in_countY_preset
>>> +KernelVersion: 4.9
>>> +Contact: linux-iio@xxxxxxxxxxxxxxx
>>> +Description:
>>> + If the counter device supports preset registers, the preset
>>> + count for channel Y is provided by this attribute.
>>> +
>>> +What: /sys/bus/iio/devices/iio:deviceX/in_indexY_raw
>>> +KernelVersion: 4.9
>>> +Contact: linux-iio@xxxxxxxxxxxxxxx
>>> +Description:
>>> + Raw counter device index value from channel Y.
>> Needs more description. Don't assume people have any idea what an 'index'
>> value is on a counter.
>>> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
>>> index fc340ed..ed175a2 100644
>>> --- a/drivers/iio/industrialio-core.c
>>> +++ b/drivers/iio/industrialio-core.c
>>> @@ -81,6 +81,8 @@ static const char * const iio_chan_type_name_spec[] = {
>>> [IIO_PH] = "ph",
>>> [IIO_UVINDEX] = "uvindex",
>>> [IIO_ELECTRICALCONDUCTIVITY] = "electricalconductivity",
>>> + [IIO_COUNT] = "count",
>>> + [IIO_INDEX] = "index",
>>> };
>>>
>>> static const char * const iio_modifier_names[] = {
>>> @@ -151,6 +153,7 @@ static const char * const iio_chan_info_postfix[] = {
>>> [IIO_CHAN_INFO_DEBOUNCE_TIME] = "debounce_time",
>>> [IIO_CHAN_INFO_CALIBEMISSIVITY] = "calibemissivity",
>>> [IIO_CHAN_INFO_OVERSAMPLING_RATIO] = "oversampling_ratio",
>>> + [IIO_CHAN_INFO_PRESET] = "preset",
>>> };
>>>
>>> /**
>>> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
>>> index b4a0679..7dc86d1 100644
>>> --- a/include/linux/iio/iio.h
>>> +++ b/include/linux/iio/iio.h
>>> @@ -46,6 +46,7 @@ enum iio_chan_info_enum {
>>> IIO_CHAN_INFO_DEBOUNCE_TIME,
>>> IIO_CHAN_INFO_CALIBEMISSIVITY,
>>> IIO_CHAN_INFO_OVERSAMPLING_RATIO,
>>> + IIO_CHAN_INFO_PRESET,
>>> };
>>>
>>> enum iio_shared_by {
>>> diff --git a/include/uapi/linux/iio/types.h b/include/uapi/linux/iio/types.h
>>> index 22e5e58..e54d14a 100644
>>> --- a/include/uapi/linux/iio/types.h
>>> +++ b/include/uapi/linux/iio/types.h
>>> @@ -40,6 +40,8 @@ enum iio_chan_type {
>>> IIO_PH,
>>> IIO_UVINDEX,
>>> IIO_ELECTRICALCONDUCTIVITY,
>>> + IIO_COUNT,
>>> + IIO_INDEX,
>>> };
>>>
>>> enum iio_modifier {
>>>
>>