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SubjectRe: [PATCH v6 2/9] counter: Documentation: Add Generic Counter sysfs documentation
On Wed, 16 May 2018 13:50:55 -0400
William Breathitt Gray <vilhelm.gray@gmail.com> wrote:

> This patch adds standard documentation for the userspace sysfs
> attributes of the Generic Counter interface.
>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>

Some really minor stuff inline. No functional changes.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
> Documentation/ABI/testing/sysfs-bus-counter | 241 ++++++++++++++++++++
> MAINTAINERS | 1 +
> 2 files changed, 242 insertions(+)
> create mode 100644 Documentation/ABI/testing/sysfs-bus-counter
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter
> new file mode 100644
> index 000000000000..e4a45d231b4f
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-counter
> @@ -0,0 +1,241 @@
> +What: /sys/bus/counter/devices/counterX/countY/count
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Count data of Count Y represented as a string.
> +
> +What: /sys/bus/counter/devices/counterX/countY/ceiling
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Count value ceiling for Count Y. This is the upper limit for the
> + respective counter.
> +
> +What: /sys/bus/counter/devices/counterX/countY/floor
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Count value floor for Count Y. This is the lower limit for the
> + respective counter.
> +
> +What: /sys/bus/counter/devices/counterX/countY/count_mode
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Count mode for channel Y. The ceiling and floor values for
> + Count Y are used by the count mode where required. The following
> + count modes are available:
> +
> + Normal:
> + Counting is continuous in either direction.
> +
> + Range Limit:
> + An upper or lower limit is set, mimicking limit switches
> + in the mechanical counterpart. The upper limit is set to
> + the Count Y ceiling value, while the lower limit is set
> + to the Count Y floor value. The counter freezes at
> + count = ceiling when counting up, and at count = floor
> + when counting down. At either of these limits, the
> + counting is resumed only when the count direction is
> + reversed.
> +
> + Non-Recycle:
> + The counter is disabled whenever a counter overflow or
> + underflow takes place. The counter is re-enabled when a
> + new count value is loaded to the counter via a preset
> + operation or direct write.
> +
> + Modulo-N:
> + A count value boundary is set between the Count Y floor
> + value and the Count Y ceiling value. The counter is
> + reset to the Cunt Y floor value at count = ceiling when
> + counting up, while the counter is set to the Count Y
> + ceiling value at count = floor when counting down; the
> + counter does not freeze at the boundary points, but
> + counts continuously throughout.
> +
> +What: /sys/bus/counter/devices/counterX/countY/count_mode_available
> +What: /sys/bus/counter/devices/counterX/countY/error_noise_available
> +What: /sys/bus/counter/devices/counterX/countY/function_available
> +What: /sys/bus/counter/devices/counterX/countY/signalZ_action_available
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Discrete set of available values for the respective Count Y
> + configuration are listed in this file. Values are delineated by
> + newline characters.
> +
> +What: /sys/bus/counter/devices/counterX/countY/direction
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Read-only attribute that indicates the count direction of Count
> + Y. Two count directions are available: forward and backward.
> +
> + Some counter devices are able to determine the direction of
> + their counting. For example, quadrature encoding counters can
> + determine the direction of movement by evaluating the leading
> + phase of the respective A and B quadrature encoding signals.
> + This attribute exposes such count directions.
> +
> +What: /sys/bus/counter/devices/counterX/countY/enable
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Whether channel Y counter is enabled. Valid attribute values are
> + boolean.
> +
> + This attribute is intended to serve as a pause/unpause mechanism
> + for Count Y. Suppose a counter device is used to count the total
> + movement of a conveyor belt: this attribute allows an operator
> + to temporarily pause the counter, service the conveyor belt,
> + and then finally unpause the counter to continue where it had
> + left off.
> +
> +What: /sys/bus/counter/devices/counterX/countY/error_noise
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Read-only attribute that indicates whether excessive noise is
> + present at the channel Y counter inputs.
> +
> +What: /sys/bus/counter/devices/counterX/countY/function
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Count function mode of Count Y; count function evaluation is
> + triggered by conditions specified by the Count Y signalZ_action
> + attributes. The following count functions are available:
> +
> + Increase:
> + Accumulated count is incremented.
> +
> + Decrease:
> + Accumulated count is decremented.
> +
> + Pulse-Direction:
> + Rising edges on quadrature pair signal A updates the
> + respective count. The input level of quadrature pair
> + signal B determines direction.
> +
> + Quadrature x1 A:
> + If direction is forward, rising edges on quadrature pair
> + signal A updates the respective count; if the direction
> + is backward, falling edges on quadrature pair signal A
> + updates the respective count. Quadrature encoding
> + determines the direction.
> +
> + Quadrature x1 B:
> + If direction is forward, rising edges on quadrature pair
> + signal B updates the respective count; if the direction
> + is backward, falling edges on quadrature pair signal B
> + updates the respective count. Quadrature encoding
> + determines the direction.
> +
> + Quadrature x2 A:
> + Any state transition on quadrature pair signal A updates
> + the respective count. Quadrature encoding determines the
> + direction.
> +
> + Quadrature x2 B:
> + Any state transition on quadrature pair signal B updates
> + the respective count. Quadrature encoding determines the
> + direction.
> +
> + Quadrature x2 Rising:
> + Rising edges on either quadrature pair signals updates
> + the respective count. Quadrature encoding determines the
> + direction.
> +
> + Quadrature x2 Falling:
> + Falling edges on either quadrature pair signals updates
> + the respective count. Quadrature encoding determines the
> + direction.
> +
> + Quadrature x4:
> + Any state transition on either quadrature pair signals
> + updates the respective count. Quadrature encoding
> + determines the direction.
> +
> +What: /sys/bus/counter/devices/counterX/countY/name
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Read-only attribute that indicates the device-specific name of
> + Count Y. If possible, this should match the name of the
> + respective channel as it appears in the device datasheet
> + documentation text.
> +
> +What: /sys/bus/counter/devices/counterX/countY/preset
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + If the counter device supports preset registers, the preset
> + count for channel Y is provided by this attribute.

I would add a small block of text here saying what a "preset" typically is.
It is a term heavily used in encoders etc, but perhaps not some other types
of counter.

> +
> +What: /sys/bus/counter/devices/counterX/countY/preset_enable
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Whether channel Y counter preset operation is enabled. Valid
> + attribute values are boolean.
> +
> +What: /sys/bus/counter/devices/counterX/countY/signalZ_action
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Action mode of Count Y for Signal Z. This attribute indicates
> + the condition of Signal Z that triggers the count function
> + evaluation for Count Y. The following action modes are
> + available:
> +
> + None:
> + Signal does not trigger the count function. In
> + Pulse-Direction count function mode, this Signal is
> + evaluated as Direction.
> +
> + Rising Edge:
> + Low state transitions to high state.
> +
> + Falling Edge:
> + High state transitions to low state.
> +
> + Both Edges:
> + Any state transition.
> +
> +What: /sys/bus/counter/devices/counterX/name
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Read-only attribute that indicates the device-specific name of
> + the Counter. This should match the name of the device as it
> + appears in its respective datasheet documentation text.

As below, I'm not sure if "documentation text" makes it clearer or less clear..

> +
> +What: /sys/bus/counter/devices/counterX/num_counts
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Read-only attribute that indicates the total number of Counts
> + belonging to the Counter.
> +
> +What: /sys/bus/counter/devices/counterX/num_signals
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Read-only attribute that indicates the total number of Signals
> + belonging to the Counter.
> +
> +What: /sys/bus/counter/devices/counterX/signalY/signal
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Signal data of Signal Y represented as a string.
> +
> +What: /sys/bus/counter/devices/counterX/signalY/name
> +KernelVersion: 4.18
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Read-only attribute that indicates the device-specific name of
> + Signal Y. If possible, this should match the name of the
> + respective signal as it appears in the device datasheet
> + documentation text.

Not sure "documentation text" adds any clarity over the simply "device datasheet"

> diff --git a/MAINTAINERS b/MAINTAINERS
> index 2a016d73ab72..1413e3eb49e5 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -3673,6 +3673,7 @@ COUNTER SUBSYSTEM
> M: William Breathitt Gray <vilhelm.gray@gmail.com>
> L: linux-iio@vger.kernel.org
> S: Maintained
> +F: Documentation/ABI/testing/sysfs-bus-counter*
> F: drivers/counter/
> F: include/linux/counter.h
>

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