On Wed, 16 May 2018 13:50:55 -0400 William Breathitt Gray <[email protected]> wrote:
> This patch adds standard documentation for the userspace sysfs > attributes of the Generic Counter interface. > > Signed-off-by: William Breathitt Gray <[email protected]> Some really minor stuff inline. No functional changes. Reviewed-by: Jonathan Cameron <[email protected]> > --- > 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: [email protected] > +Description: > + Count data of Count Y represented as a string. > + > +What: /sys/bus/counter/devices/counterX/countY/ceiling > +KernelVersion: 4.18 > +Contact: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +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: [email protected] > +Description: > + Signal data of Signal Y represented as a string. > + > +What: /sys/bus/counter/devices/counterX/signalY/name > +KernelVersion: 4.18 > +Contact: [email protected] > +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 <[email protected]> > L: [email protected] > S: Maintained > +F: Documentation/ABI/testing/sysfs-bus-counter* > F: drivers/counter/ > F: include/linux/counter.h >
