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SubjectRe: [PATCH v5 2/8] counter: Documentation: Add Generic Counter sysfs documentation
On Fri,  9 Mar 2018 13:42:35 -0500
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>
Good, few comments inline.

Jonathan

> ---
> Documentation/ABI/testing/sysfs-bus-counter | 120 ++++++++++++++++++++++++++++
> MAINTAINERS | 1 +
> 2 files changed, 121 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..64785aab1763
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-counter
> @@ -0,0 +1,120 @@
> +What: /sys/bus/counter/devices/counterX/countY/count
> +KernelVersion: 4.17
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Count data of Count Y. The following data types are available:
> +
> + COUNT_POSITION_UNSIGNED:
> + Unsigned integer value representing position.
> +
> + COUNT_POSITION_SIGNED:
> + Signed integer value representing position.
Why are these data types relevant in this document?
You are outputting a string. Userspace doesn't really need to know
more than that.

> +
> +What: /sys/bus/counter/devices/counterX/countY/function
> +KernelVersion: 4.17
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Count function mode of Count Y; count function evaluation is
> + triggered by conditions specified by the countY_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:
> + 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 x2:
> + Any state transition on quadrature pair signal A 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/function_available
> +KernelVersion: 4.17
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Discrete set of available count function modes for the
> + configuration of the respective Count Y are listed in this file.
How is this list delineated? There are several competing options in different
kernel subsystems so this isn't exactly obvious ;)

> +
> +What: /sys/bus/counter/devices/counterX/countY/name
> +KernelVersion: 4.17
> +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/signalZ_action
> +KernelVersion: 4.17
> +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/countY/signalZ_action_available
> +KernelVersion: 4.17
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Discrete set of available action modes are listed in this file
> + for the configuration of the respective Synapse associating
> + Signal Z to Count Y.
> +
> +What: /sys/bus/counter/devices/counterX/name
> +KernelVersion: 4.17
> +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.
> +
> +What: /sys/bus/counter/devices/counterX/signalY/signal
> +KernelVersion: 4.17
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Signal data of Signal Y. The following data types are available:
> +
> + SIGNAL_LEVEL:
> + Respective input has two discrete states: Low and High.
Formatting is rather inconsistent. For the type we had Capital then lowercase
here all caps? Or is this an integer from an enum? Definitely prefer
a human readable version if possible This is also rather pointless until
we have more than one option ;)

> +
> +What: /sys/bus/counter/devices/counterX/signalY/name
> +KernelVersion: 4.17
> +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.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 2be01a95b7a5..2a7bf2f84272 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -3672,6 +3672,7 @@ 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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