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diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst index 8382f01a53e3..e622f8f6e56a 100644 --- a/Documentation/driver-api/generic-counter.rst +++ b/Documentation/driver-api/generic-counter.rst @@ -7,7 +7,7 @@ Generic Counter Interface Introduction ============ -Counter devices are prevalent within a diverse spectrum of industries. +Counter devices are prevalent among a diverse spectrum of industries. The ubiquitous presence of these devices necessitates a common interface and standard of interaction and exposure. This driver API attempts to resolve the issue of duplicate code found among existing counter device @@ -26,23 +26,72 @@ the Generic Counter interface. There are three core components to a counter: -* Count: - Count data for a set of Signals. - * Signal: - Input data that is evaluated by the counter to determine the count - data. + Stream of data to be evaluated by the counter. * Synapse: - The association of a Signal with a respective Count. + Association of a Signal, and evaluation trigger, with a Count. + +* Count: + Accumulation of the effects of connected Synapses. + +SIGNAL +------ +A Signal represents a stream of data. This is the input data that is +evaluated by the counter to determine the count data; e.g. a quadrature +signal output line of a rotary encoder. Not all counter devices provide +user access to the Signal data, so exposure is optional for drivers. + +When the Signal data is available for user access, the Generic Counter +interface provides the following available signal values: + +* SIGNAL_LOW: + Signal line is in a low state. + +* SIGNAL_HIGH: + Signal line is in a high state. + +A Signal may be associated with one or more Counts. + +SYNAPSE +------- +A Synapse represents the association of a Signal with a Count. Signal +data affects respective Count data, and the Synapse represents this +relationship. + +The Synapse action mode specifies the Signal data condition that +triggers the respective Count's count function evaluation to update the +count data. The Generic Counter interface provides the following +available action modes: + +* 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. + +A counter is defined as a set of input signals associated with count +data that are generated by the evaluation of the state of the associated +input signals as defined by the respective count functions. Within the +context of the Generic Counter interface, a counter consists of Counts +each associated with a set of Signals, whose respective Synapse +instances represent the count function update conditions for the +associated Counts. + +A Synapse associates one Signal with one Count. COUNT ----- -A Count represents the count data for a set of Signals. The Generic -Counter interface provides the following available count data types: - -* COUNT_POSITION: - Unsigned integer value representing position. +A Count represents the accumulation of the effects of connected +Synapses; i.e. the count data for a set of Signals. The Generic +Counter interface represents the count data as a natural number. A Count has a count function mode which represents the update behavior for the count data. The Generic Counter interface provides the following @@ -86,60 +135,7 @@ available count function modes: Any state transition on either quadrature pair signals updates the respective count. Quadrature encoding determines the direction. -A Count has a set of one or more associated Signals. - -SIGNAL ------- -A Signal represents a counter input data; this is the input data that is -evaluated by the counter to determine the count data; e.g. a quadrature -signal output line of a rotary encoder. Not all counter devices provide -user access to the Signal data. - -The Generic Counter interface provides the following available signal -data types for when the Signal data is available for user access: - -* SIGNAL_LEVEL: - Signal line state level. The following states are possible: - - - SIGNAL_LEVEL_LOW: - Signal line is in a low state. - - - SIGNAL_LEVEL_HIGH: - Signal line is in a high state. - -A Signal may be associated with one or more Counts. - -SYNAPSE -------- -A Synapse represents the association of a Signal with a respective -Count. Signal data affects respective Count data, and the Synapse -represents this relationship. - -The Synapse action mode specifies the Signal data condition which -triggers the respective Count's count function evaluation to update the -count data. The Generic Counter interface provides the following -available action modes: - -* 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. - -A counter is defined as a set of input signals associated with count -data that are generated by the evaluation of the state of the associated -input signals as defined by the respective count functions. Within the -context of the Generic Counter interface, a counter consists of Counts -each associated with a set of Signals, whose respective Synapse -instances represent the count function update conditions for the -associated Counts. +A Count has a set of one or more associated Synapses. Paradigm ======== @@ -286,10 +282,36 @@ if device memory-managed registration is desired. Extension sysfs attributes can be created for auxiliary functionality and data by passing in defined counter_device_ext, counter_count_ext, and counter_signal_ext structures. In these cases, the -counter_device_ext structure is used for global configuration of the -respective Counter device, while the counter_count_ext and -counter_signal_ext structures allow for auxiliary exposure and -configuration of a specific Count or Signal respectively. +counter_device_ext structure is used for global/miscellaneous exposure +and configuration of the respective Counter device, while the +counter_count_ext and counter_signal_ext structures allow for auxiliary +exposure and configuration of a specific Count or Signal respectively. + +Determining the type of extension to create is a matter of scope. + +* Signal extensions are attributes that expose information/control + specific to a Signal. These types of attributes will exist under a + Signal's directory in sysfs. + + For example, if you have an invert feature for a Signal, you can have + a Signal extension called "invert" that toggles that feature: + /sys/bus/counter/devices/counterX/signalY/invert + +* Count extensions are attributes that expose information/control + specific to a Count. These type of attributes will exist under a + Count's directory in sysfs. + + For example, if you want to pause/unpause a Count from updating, you + can have a Count extension called "enable" that toggles such: + /sys/bus/counter/devices/counterX/countY/enable + +* Device extensions are attributes that expose information/control + non-specific to a particular Count or Signal. This is where you would + put your global features or other miscellanous functionality. + + For example, if your device has an overtemp sensor, you can report the + chip overheated via a device extension called "error_overtemp": + /sys/bus/counter/devices/counterX/error_overtemp Architecture ============ |