| Message ID | 4a1bdcdea3826d9b1a8af3d9318ac952693f400c.1608935587.git.vilhelm.gray@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Introduce the Counter character device interface | expand |
On Fri, 25 Dec 2020 19:15:35 -0500 William Breathitt Gray <vilhelm.gray@gmail.com> wrote: > The Counter subsystem architecture and driver implementations have > changed in order to handle Counter sysfs interactions in a more > consistent way. This patch updates the Generic Counter interface > documentation to reflect the changes. > > Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com> > --- > Documentation/ABI/testing/sysfs-bus-counter | 9 +- > Documentation/driver-api/generic-counter.rst | 242 ++++++++++++++----- > 2 files changed, 184 insertions(+), 67 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter > index 566bd99fe0a5..1820ce2f9183 100644 > --- a/Documentation/ABI/testing/sysfs-bus-counter > +++ b/Documentation/ABI/testing/sysfs-bus-counter > @@ -219,7 +219,14 @@ What: /sys/bus/counter/devices/counterX/signalY/signal > KernelVersion: 5.2 > Contact: linux-iio@vger.kernel.org > Description: > - Signal data of Signal Y represented as a string. > + Signal level state of Signal Y. The following signal level > + states are available: > + > + low: > + Low level state. > + > + high: > + High level state. > > What: /sys/bus/counter/devices/counterX/signalY/name > KernelVersion: 5.2 > diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst > index b02c52cd69d6..b842ddbbd8a0 100644 > --- a/Documentation/driver-api/generic-counter.rst > +++ b/Documentation/driver-api/generic-counter.rst > @@ -250,8 +250,8 @@ for defining a counter device. > .. kernel-doc:: drivers/counter/counter.c > :export: > > -Implementation > -============== > +Driver Implementation > +===================== > > To support a counter device, a driver must first allocate the available > Counter Signals via counter_signal structures. These Signals should > @@ -267,25 +267,59 @@ respective counter_count structure. These counter_count structures are > set to the counts array member of an allocated counter_device structure > before the Counter is registered to the system. > > -Driver callbacks should be provided to the counter_device structure via > -a constant counter_ops structure in order to communicate with the > -device: to read and write various Signals and Counts, and to set and get > -the "action mode" and "function mode" for various Synapses and Counts > -respectively. > +Driver callbacks must be provided to the counter_device structure in > +order to communicate with the device: to read and write various Signals > +and Counts, and to set and get the "action mode" and "function mode" for > +various Synapses and Counts respectively. > > A defined counter_device structure may be registered to the system by > passing it to the counter_register function, and unregistered by passing > it to the counter_unregister function. Similarly, the > -devm_counter_register and devm_counter_unregister functions may be used > -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/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. > +devm_counter_register function may be used if device memory-managed > +registration is desired. > + > +The struct counter_comp structure is used to define counter extensions > +for Signals, Synapses, and Counts. > + > +The "type" member specifies the type of high-level data (e.g. BOOL, > +COUNT_DIRECTION, etc.) handled by this extension. The "`*_read`" and > +"`*_write`" members can then be set by the counter device driver with > +callbacks to handle that data using native C data types (i.e. u8, u64, > +etc.). > + > +Convenience macros such as `COUNTER_COMP_COUNT_U64` are provided for use > +by driver authors. In particular, driver authors are expected to use > +the provided macros for standard Counter subsystem attributes in order > +to maintain a consistent interface for userspace. For example, a counter > +device driver may define several standard attributes like so:: > + > + struct counter_comp count_ext[] = { > + COUNTER_COMP_DIRECTION(count_direction_read), > + COUNTER_COMP_ENABLE(count_enable_read, count_enable_write), > + COUNTER_COMP_CEILING(count_ceiling_read, count_ceiling_write), > + }; > + > +This makes it simple to see, add, and modify the attributes that are > +supported by this driver ("direction", "enable", and "ceiling") and to > +maintain this code without getting lost in a web of struct braces. > + > +Callbacks must match the function type expected for the respective > +component or extension. These function types are defined in the struct > +counter_comp structure as the "`*_read`" and "`*_write`" union members. > + > +The corresponding callback prototypes for the extensions mentioned in > +the previous example above would be:: > + > + int count_direction_read(struct counter_device *counter, > + struct counter_count *count, u8 *direction); > + int count_enable_read(struct counter_device *counter, > + struct counter_count *count, u8 *enable); > + int count_enable_write(struct counter_device *counter, > + struct counter_count *count, u8 enable); > + int count_ceiling_read(struct counter_device *counter, > + struct counter_count *count, u64 *ceiling); > + int count_ceiling_write(struct counter_device *counter, > + struct counter_count *count, u64 ceiling); > > Determining the type of extension to create is a matter of scope. > > @@ -313,52 +347,128 @@ Determining the type of extension to create is a matter of scope. > chip overheated via a device extension called "error_overtemp": > /sys/bus/counter/devices/counterX/error_overtemp > > -Architecture > -============ > - > -When the Generic Counter interface counter module is loaded, the > -counter_init function is called which registers a bus_type named > -"counter" to the system. Subsequently, when the module is unloaded, the > -counter_exit function is called which unregisters the bus_type named > -"counter" from the system. > - > -Counter devices are registered to the system via the counter_register > -function, and later removed via the counter_unregister function. The > -counter_register function establishes a unique ID for the Counter > -device and creates a respective sysfs directory, where X is the > -mentioned unique ID: > - > - /sys/bus/counter/devices/counterX > - > -Sysfs attributes are created within the counterX directory to expose > -functionality, configurations, and data relating to the Counts, Signals, > -and Synapses of the Counter device, as well as options and information > -for the Counter device itself. > - > -Each Signal has a directory created to house its relevant sysfs > -attributes, where Y is the unique ID of the respective Signal: > - > - /sys/bus/counter/devices/counterX/signalY > - > -Similarly, each Count has a directory created to house its relevant > -sysfs attributes, where Y is the unique ID of the respective Count: > - > - /sys/bus/counter/devices/counterX/countY > - > -For a more detailed breakdown of the available Generic Counter interface > -sysfs attributes, please refer to the > -Documentation/ABI/testing/sysfs-bus-counter file. > - > -The Signals and Counts associated with the Counter device are registered > -to the system as well by the counter_register function. The > -signal_read/signal_write driver callbacks are associated with their > -respective Signal attributes, while the count_read/count_write and > -function_get/function_set driver callbacks are associated with their > -respective Count attributes; similarly, the same is true for the > -action_get/action_set driver callbacks and their respective Synapse > -attributes. If a driver callback is left undefined, then the respective > -read/write permission is left disabled for the relevant attributes. > - > -Similarly, extension sysfs attributes are created for the defined > -counter_device_ext, counter_count_ext, and counter_signal_ext > -structures that are passed in. > +Subsystem Architecture > +====================== > + > +Counter drivers pass and take data natively (i.e. `u8`, `u64`, etc.) and > +the shared counter module handles the translation between the sysfs > +interface. Same point as raised in previous patch description. > This gurantees a standard userspace interface for all counter Spell check this file. guarantees > +drivers, and helps generalize the Generic Counter driver ABI in order to > +support the Generic Counter chrdev interface without significant changes > +to the existing counter drivers. I would modify this to assume you've already done the chrdev interface. "and enables a Generic Counter chrdev interface without..." > + > +A high-level view of how a count value is passed down from a counter > +driver is exemplified by the following. The driver callbacks are first > +registered to the Counter core component for use by the Counter > +userspace interface components:: > + > + Driver callbacks registration: > + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > + +----------------------------+ > + | Counter device driver | That tab again ;) > + +----------------------------+ > + | Processes data from device | > + +----------------------------+ > + | > + ------------------- > + / driver callbacks / > + ------------------- > + | > + V > + +----------------------+ > + | Counter core | > + +----------------------+ > + | Routes device driver | > + | callbacks to the | > + | userspace interfaces | > + +----------------------+ > + | > + ------------------- > + / driver callbacks / > + ------------------- > + | > + +---------------+ > + | > + V > + +--------------------+ > + | Counter sysfs | > + +--------------------+ > + | Translates to the | > + | standard Counter | > + | sysfs output | > + +--------------------+ > + > +Thereafter, data can be transferred directly between the Counter device > +driver and Counter userspace interface:: > + > + Count data request: > + ~~~~~~~~~~~~~~~~~~~ > + ---------------------- > + / Counter device \ > + +----------------------+ > + | Count register: 0x28 | > + +----------------------+ > + | > + ----------------- > + / raw count data / > + ----------------- > + | > + V > + +----------------------------+ > + | Counter device driver | > + +----------------------------+ > + | Processes data from device | > + |----------------------------| > + | Type: u64 | > + | Value: 42 | > + +----------------------------+ > + | > + ---------- > + / u64 / > + ---------- > + | > + +---------------+ > + | > + V > + +--------------------+ > + | Counter sysfs | > + +--------------------+ > + | Translates to the | > + | standard Counter | > + | sysfs output | > + |--------------------| > + | Type: const char * | > + | Value: "42" | > + +--------------------+ > + | > + --------------- > + / const char * / > + --------------- > + | > + V > + +--------------------------------------------------+ > + | `/sys/bus/counter/devices/counterX/countY/count` | > + +--------------------------------------------------+ > + \ Count: "42" / > + -------------------------------------------------- > + > +There are three primary components involved: > + > +Counter device driver > +--------------------- > +Communicates with the hardware device to read/write data; e.g. counter > +drivers for quadrature encoders, timers, etc. > + > +Counter core > +------------ > +Registers the counter device driver to the system so that the respective > +callbacks are called during userspace interaction. > + > +Counter sysfs > +------------- > +Translates counter data to the standard Counter sysfs interface format > +and vice versa. > + > +Please refer to the `Documentation/ABI/testing/sysfs-bus-counter` file > +for a detailed breakdown of the available Generic Counter interface > +sysfs attributes. Otherwise LGTM. Thanks, Jonathan
diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter index 566bd99fe0a5..1820ce2f9183 100644 --- a/Documentation/ABI/testing/sysfs-bus-counter +++ b/Documentation/ABI/testing/sysfs-bus-counter @@ -219,7 +219,14 @@ What: /sys/bus/counter/devices/counterX/signalY/signal KernelVersion: 5.2 Contact: linux-iio@vger.kernel.org Description: - Signal data of Signal Y represented as a string. + Signal level state of Signal Y. The following signal level + states are available: + + low: + Low level state. + + high: + High level state. What: /sys/bus/counter/devices/counterX/signalY/name KernelVersion: 5.2 diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst index b02c52cd69d6..b842ddbbd8a0 100644 --- a/Documentation/driver-api/generic-counter.rst +++ b/Documentation/driver-api/generic-counter.rst @@ -250,8 +250,8 @@ for defining a counter device. .. kernel-doc:: drivers/counter/counter.c :export: -Implementation -============== +Driver Implementation +===================== To support a counter device, a driver must first allocate the available Counter Signals via counter_signal structures. These Signals should @@ -267,25 +267,59 @@ respective counter_count structure. These counter_count structures are set to the counts array member of an allocated counter_device structure before the Counter is registered to the system. -Driver callbacks should be provided to the counter_device structure via -a constant counter_ops structure in order to communicate with the -device: to read and write various Signals and Counts, and to set and get -the "action mode" and "function mode" for various Synapses and Counts -respectively. +Driver callbacks must be provided to the counter_device structure in +order to communicate with the device: to read and write various Signals +and Counts, and to set and get the "action mode" and "function mode" for +various Synapses and Counts respectively. A defined counter_device structure may be registered to the system by passing it to the counter_register function, and unregistered by passing it to the counter_unregister function. Similarly, the -devm_counter_register and devm_counter_unregister functions may be used -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/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. +devm_counter_register function may be used if device memory-managed +registration is desired. + +The struct counter_comp structure is used to define counter extensions +for Signals, Synapses, and Counts. + +The "type" member specifies the type of high-level data (e.g. BOOL, +COUNT_DIRECTION, etc.) handled by this extension. The "`*_read`" and +"`*_write`" members can then be set by the counter device driver with +callbacks to handle that data using native C data types (i.e. u8, u64, +etc.). + +Convenience macros such as `COUNTER_COMP_COUNT_U64` are provided for use +by driver authors. In particular, driver authors are expected to use +the provided macros for standard Counter subsystem attributes in order +to maintain a consistent interface for userspace. For example, a counter +device driver may define several standard attributes like so:: + + struct counter_comp count_ext[] = { + COUNTER_COMP_DIRECTION(count_direction_read), + COUNTER_COMP_ENABLE(count_enable_read, count_enable_write), + COUNTER_COMP_CEILING(count_ceiling_read, count_ceiling_write), + }; + +This makes it simple to see, add, and modify the attributes that are +supported by this driver ("direction", "enable", and "ceiling") and to +maintain this code without getting lost in a web of struct braces. + +Callbacks must match the function type expected for the respective +component or extension. These function types are defined in the struct +counter_comp structure as the "`*_read`" and "`*_write`" union members. + +The corresponding callback prototypes for the extensions mentioned in +the previous example above would be:: + + int count_direction_read(struct counter_device *counter, + struct counter_count *count, u8 *direction); + int count_enable_read(struct counter_device *counter, + struct counter_count *count, u8 *enable); + int count_enable_write(struct counter_device *counter, + struct counter_count *count, u8 enable); + int count_ceiling_read(struct counter_device *counter, + struct counter_count *count, u64 *ceiling); + int count_ceiling_write(struct counter_device *counter, + struct counter_count *count, u64 ceiling); Determining the type of extension to create is a matter of scope. @@ -313,52 +347,128 @@ Determining the type of extension to create is a matter of scope. chip overheated via a device extension called "error_overtemp": /sys/bus/counter/devices/counterX/error_overtemp -Architecture -============ - -When the Generic Counter interface counter module is loaded, the -counter_init function is called which registers a bus_type named -"counter" to the system. Subsequently, when the module is unloaded, the -counter_exit function is called which unregisters the bus_type named -"counter" from the system. - -Counter devices are registered to the system via the counter_register -function, and later removed via the counter_unregister function. The -counter_register function establishes a unique ID for the Counter -device and creates a respective sysfs directory, where X is the -mentioned unique ID: - - /sys/bus/counter/devices/counterX - -Sysfs attributes are created within the counterX directory to expose -functionality, configurations, and data relating to the Counts, Signals, -and Synapses of the Counter device, as well as options and information -for the Counter device itself. - -Each Signal has a directory created to house its relevant sysfs -attributes, where Y is the unique ID of the respective Signal: - - /sys/bus/counter/devices/counterX/signalY - -Similarly, each Count has a directory created to house its relevant -sysfs attributes, where Y is the unique ID of the respective Count: - - /sys/bus/counter/devices/counterX/countY - -For a more detailed breakdown of the available Generic Counter interface -sysfs attributes, please refer to the -Documentation/ABI/testing/sysfs-bus-counter file. - -The Signals and Counts associated with the Counter device are registered -to the system as well by the counter_register function. The -signal_read/signal_write driver callbacks are associated with their -respective Signal attributes, while the count_read/count_write and -function_get/function_set driver callbacks are associated with their -respective Count attributes; similarly, the same is true for the -action_get/action_set driver callbacks and their respective Synapse -attributes. If a driver callback is left undefined, then the respective -read/write permission is left disabled for the relevant attributes. - -Similarly, extension sysfs attributes are created for the defined -counter_device_ext, counter_count_ext, and counter_signal_ext -structures that are passed in. +Subsystem Architecture +====================== + +Counter drivers pass and take data natively (i.e. `u8`, `u64`, etc.) and +the shared counter module handles the translation between the sysfs +interface. This gurantees a standard userspace interface for all counter +drivers, and helps generalize the Generic Counter driver ABI in order to +support the Generic Counter chrdev interface without significant changes +to the existing counter drivers. + +A high-level view of how a count value is passed down from a counter +driver is exemplified by the following. The driver callbacks are first +registered to the Counter core component for use by the Counter +userspace interface components:: + + Driver callbacks registration: + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +----------------------------+ + | Counter device driver | + +----------------------------+ + | Processes data from device | + +----------------------------+ + | + ------------------- + / driver callbacks / + ------------------- + | + V + +----------------------+ + | Counter core | + +----------------------+ + | Routes device driver | + | callbacks to the | + | userspace interfaces | + +----------------------+ + | + ------------------- + / driver callbacks / + ------------------- + | + +---------------+ + | + V + +--------------------+ + | Counter sysfs | + +--------------------+ + | Translates to the | + | standard Counter | + | sysfs output | + +--------------------+ + +Thereafter, data can be transferred directly between the Counter device +driver and Counter userspace interface:: + + Count data request: + ~~~~~~~~~~~~~~~~~~~ + ---------------------- + / Counter device \ + +----------------------+ + | Count register: 0x28 | + +----------------------+ + | + ----------------- + / raw count data / + ----------------- + | + V + +----------------------------+ + | Counter device driver | + +----------------------------+ + | Processes data from device | + |----------------------------| + | Type: u64 | + | Value: 42 | + +----------------------------+ + | + ---------- + / u64 / + ---------- + | + +---------------+ + | + V + +--------------------+ + | Counter sysfs | + +--------------------+ + | Translates to the | + | standard Counter | + | sysfs output | + |--------------------| + | Type: const char * | + | Value: "42" | + +--------------------+ + | + --------------- + / const char * / + --------------- + | + V + +--------------------------------------------------+ + | `/sys/bus/counter/devices/counterX/countY/count` | + +--------------------------------------------------+ + \ Count: "42" / + -------------------------------------------------- + +There are three primary components involved: + +Counter device driver +--------------------- +Communicates with the hardware device to read/write data; e.g. counter +drivers for quadrature encoders, timers, etc. + +Counter core +------------ +Registers the counter device driver to the system so that the respective +callbacks are called during userspace interaction. + +Counter sysfs +------------- +Translates counter data to the standard Counter sysfs interface format +and vice versa. + +Please refer to the `Documentation/ABI/testing/sysfs-bus-counter` file +for a detailed breakdown of the available Generic Counter interface +sysfs attributes.
The Counter subsystem architecture and driver implementations have changed in order to handle Counter sysfs interactions in a more consistent way. This patch updates the Generic Counter interface documentation to reflect the changes. Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com> --- Documentation/ABI/testing/sysfs-bus-counter | 9 +- Documentation/driver-api/generic-counter.rst | 242 ++++++++++++++----- 2 files changed, 184 insertions(+), 67 deletions(-)