| Message ID | 1e69b7beae4cf352bddb379220d0d52b20db0634.1608935587.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 19:15:37 -0500 William Breathitt Gray <vilhelm.gray@gmail.com> wrote: > This patch adds high-level documentation about the Counter subsystem > character device interface. > > Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com> > --- > Documentation/ABI/testing/sysfs-bus-counter | 9 + > Documentation/driver-api/generic-counter.rst | 236 +++++++++++++++--- > .../userspace-api/ioctl/ioctl-number.rst | 1 + > 3 files changed, 205 insertions(+), 41 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter > index 1820ce2f9183..8f6ea0a50b75 100644 > --- a/Documentation/ABI/testing/sysfs-bus-counter > +++ b/Documentation/ABI/testing/sysfs-bus-counter > @@ -99,6 +99,15 @@ Description: > Read-only attribute that indicates whether excessive noise is > present at the channel Y counter inputs. > > +What: /sys/bus/counter/devices/counterX/countY/extensionZ_name > +What: /sys/bus/counter/devices/counterX/extensionZ_name > +What: /sys/bus/counter/devices/counterX/signalY/extensionZ_name > +KernelVersion: 5.12 > +Contact: linux-iio@vger.kernel.org > +Description: > + Read-only attribute that indicates the component name of > + Extension Z. Dumb question, but why is this only related to character device introduction? > + > What: /sys/bus/counter/devices/counterX/countY/function > KernelVersion: 5.2 > Contact: linux-iio@vger.kernel.org > diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst > index b842ddbbd8a0..4775dcaff557 100644 > --- a/Documentation/driver-api/generic-counter.rst > +++ b/Documentation/driver-api/generic-counter.rst > @@ -223,19 +223,6 @@ whether an input line is differential or single-ended) and instead focus > on the core idea of what the data and process represent (e.g. position > as interpreted from quadrature encoding data). > > -Userspace Interface > -=================== > - > -Several sysfs attributes are generated by the Generic Counter interface, > -and reside under the /sys/bus/counter/devices/counterX directory, where > -counterX refers to the respective counter device. Please see > -Documentation/ABI/testing/sysfs-bus-counter for detailed > -information on each Generic Counter interface sysfs attribute. > - > -Through these sysfs attributes, programs and scripts may interact with > -the Generic Counter paradigm Counts, Signals, and Synapses of respective > -counter devices. > - > Driver API > ========== > > @@ -387,16 +374,16 @@ userspace interface components:: > / driver callbacks / > ------------------- > | > - +---------------+ > - | > - V > - +--------------------+ > - | Counter sysfs | > - +--------------------+ > - | Translates to the | > - | standard Counter | > - | sysfs output | > - +--------------------+ > + +---------------+---------------+ > + | | > + V V > + +--------------------+ +---------------------+ > + | Counter sysfs | | Counter chrdev | > + +--------------------+ +---------------------+ > + | Translates to the | | Translates to the | > + | standard Counter | | standard Counter | > + | sysfs output | | character device | > + +--------------------+ +---------------------+ > > Thereafter, data can be transferred directly between the Counter device > driver and Counter userspace interface:: > @@ -427,23 +414,30 @@ driver and Counter userspace interface:: > / u64 / > ---------- > | > - +---------------+ > - | > - V > - +--------------------+ > - | Counter sysfs | > - +--------------------+ > - | Translates to the | > - | standard Counter | > - | sysfs output | > - |--------------------| > - | Type: const char * | > - | Value: "42" | > - +--------------------+ > - | > - --------------- > - / const char * / > - --------------- > + +---------------+---------------+ > + | | > + V V > + +--------------------+ +---------------------+ > + | Counter sysfs | | Counter chrdev | > + +--------------------+ +---------------------+ > + | Translates to the | | Translates to the | > + | standard Counter | | standard Counter | > + | sysfs output | | character device | > + |--------------------| |---------------------| > + | Type: const char * | | Type: u64 | > + | Value: "42" | | Value: 42 | > + +--------------------+ +---------------------+ > + | | > + --------------- ----------------------- > + / const char * / / struct counter_event / > + --------------- ----------------------- > + | | > + | V > + | +-----------+ > + | | read | > + | +-----------+ > + | \ Count: 42 / > + | ----------- > | > V > +--------------------------------------------------+ > @@ -452,7 +446,7 @@ driver and Counter userspace interface:: > \ Count: "42" / > -------------------------------------------------- > > -There are three primary components involved: > +There are four primary components involved: > > Counter device driver > --------------------- > @@ -472,3 +466,163 @@ 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. > + > +Counter chrdev > +-------------- > +Translates counter data to the standard Counter character device; data > +is transferred via standard character device read calls, while Counter > +events are configured via ioctl calls. > + > +Sysfs Interface > +=============== > + > +Several sysfs attributes are generated by the Generic Counter interface, > +and reside under the `/sys/bus/counter/devices/counterX` directory, > +where `X` is to the respective counter device id. Please see > +`Documentation/ABI/testing/sysfs-bus-counter` for detailed information > +on each Generic Counter interface sysfs attribute. > + > +Through these sysfs attributes, programs and scripts may interact with > +the Generic Counter paradigm Counts, Signals, and Synapses of respective > +counter devices. > + > +Counter Character Device > +======================== > + > +Counter character device nodes are created under the `/dev` directory as > +`counterX`, where `X` is the respective counter device id. Defines for > +the standard Counter data types are exposed via the userspace > +`include/uapi/linux/counter.h` file. > + > +Counter events > +-------------- > +Counter device drivers can support Counter events by utilizing the > +`counter_push_event` function:: > + > + int counter_push_event(struct counter_device *const counter, const u8 event, > + const u8 channel); > + > +The event id is specified by the `event` parameter; the event channel id > +is specified by the `channel` parameter. When this function is called, > +the Counter data associated with the respective event is gathered, and a > +`struct counter_event` is generated for each datum and pushed to > +userspace. > + > +Counter events can be configured by users to report various Counter > +data of interest. This can be conceptualized as a list of Counter > +component read calls to perform. For example:: > + > + +~~~~~~~~~~~~~~~~~~~~~~~~+~~~~~~~~~~~~~~~~~~~~~~~~+ > + | COUNTER_EVENT_OVERFLOW | COUNTER_EVENT_INDEX | > + +~~~~~~~~~~~~~~~~~~~~~~~~+~~~~~~~~~~~~~~~~~~~~~~~~+ > + | Channel 0 | Channel 0 | > + +------------------------+------------------------+ > + | * Count 0 | * Signal 0 | > + | * Count 1 | * Signal 0 Extension 0 | > + | * Signal 3 | * Extension 4 | > + | * Count 4 Extension 2 +------------------------+ > + | * Signal 5 Extension 0 | Channel 1 | > + | +------------------------+ > + | | * Signal 4 | > + | | * Signal 4 Extension 0 | > + | | * Count 7 | > + +------------------------+------------------------+ > + > +When `counter_push_event(counter, COUNTER_EVENT_INDEX, 1)` is called for > +example, it will go down the list for the `COUNTER_EVENT_INDEX` event > +channel 1 and execute the read callbacks for Signal 4, Signal 4 > +Extension 0, and Count 4 -- the data returned for each is pushed to a > +kfifo as a `struct counter_event`, which userspace can retrieve via a > +standard read operation on the respective character device node. > + > +Userspace > +--------- > +Userspace applications can configure Counter events via ioctl operations > +on the Counter character device node. There following ioctl codes are > +supported and provided by the `linux/counter.h` userspace header file: > + > +* COUNTER_CLEAR_WATCHES_IOCTL: > + Clear all Counter watches from all events > + > +* COUNTER_ADD_WATCH_IOCTL: > + Add a Counter watch for the specified event > + > +* COUNTER_LOAD_WATCHES_IOCTL: > + Activates the Counter watches added earlier > + > +To configure events to gather Counter data, users first populate a > +`struct counter_watch` with the relevant event id, event channel id, and > +the information for the desired Counter component from which to read, > +and then pass it via the `COUNTER_ADD_WATCH_IOCTL` ioctl command. > + > +Note that an event can be watched without gathering Counter data by > +setting the `component.type` member equal to `COUNTER_COMPONENT_NONE`. > +With this configuration the Counter character device will simply > +populate the event timestamps for those respective > +`struct counter_event` elements and ignore the component value. > + > +The `COUNTER_ADD_WATCH_IOCTL` command will buffer these Counter watches. > +When ready, the `COUNTER_LOAD_WATCHES_IOCTL` ioctl command may be used > +to activate these Counter watches. > + > +Userspace applications can then execute a `read` operation (optionally > +calling `poll` first) on the Counter character device node to retrieve > +`struct counter_event` elements with the desired data. > + > +For example, the following userspace code opens `/dev/counter0`, > +configures the `COUNTER_EVENT_INDEX` event channel 0 to gather Count 0 > +and Count 1, and prints out the data as it becomes available on the > +character device node:: > + > + #include <fcntl.h> > + #include <linux/counter.h> > + #include <stdio.h> > + #include <string.h> > + #include <sys/ioctl.h> > + #include <unistd.h> > + > + struct counter_watch watches[2] = { > + { > + .component.type = COUNTER_COMPONENT_COUNT, > + .component.scope = COUNTER_SCOPE_COUNT, > + .component.parent = 0, > + .event = COUNTER_EVENT_INDEX, > + .channel = 0, > + }, > + { > + .component.type = COUNTER_COMPONENT_COUNT, > + .component.scope = COUNTER_SCOPE_COUNT, > + .component.parent = 1, > + .event = COUNTER_EVENT_INDEX, > + .channel = 0, > + }, > + }; > + > + int main(void) > + { > + int fd; > + struct counter_event event_data[2]; > + > + fd = open("/dev/counter0", O_RDWR); > + > + ioctl(fd, COUNTER_ADD_WATCH_IOCTL, watches); > + ioctl(fd, COUNTER_ADD_WATCH_IOCTL, watches + 1); > + ioctl(fd, COUNTER_LOAD_WATCHES_IOCTL); > + > + for (;;) { > + read(fd, event_data, sizeof(event_data)); > + > + printf("Timestamp 0: %llu\tCount 0: %llu\n" > + "Error Message 0: %s\n" > + "Timestamp 1: %llu\tCount 1: %llu\n" > + "Error Message 1: %s\n", > + (unsigned long long)event_data[0].timestamp, > + (unsigned long long)event_data[0].value, > + strerror(event_data[0].errno), > + (unsigned long long)event_data[1].timestamp, > + (unsigned long long)event_data[1].value, > + strerror(event_data[1].errno)); > + } > + > + return 0; > + } > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst > index 55a2d9b2ce33..b7761ceb82a7 100644 > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst > @@ -88,6 +88,7 @@ Code Seq# Include File Comments > <http://infiniband.sourceforge.net/> > 0x20 all drivers/cdrom/cm206.h > 0x22 all scsi/sg.h > +0x3E 00-0F linux/counter.h <mailto:linux-iio@vger.kernel.org> > '!' 00-1F uapi/linux/seccomp.h > '#' 00-3F IEEE 1394 Subsystem > Block for the entire subsystem
On 12/25/20 6:15 PM, William Breathitt Gray wrote: > +Userspace > +--------- > +Userspace applications can configure Counter events via ioctl operations > +on the Counter character device node. There following ioctl codes are > +supported and provided by the `linux/counter.h` userspace header file: > + > +* COUNTER_CLEAR_WATCHES_IOCTL: > + Clear all Counter watches from all events > + > +* COUNTER_ADD_WATCH_IOCTL: > + Add a Counter watch for the specified event > + > +* COUNTER_LOAD_WATCHES_IOCTL: > + Activates the Counter watches added earlier Would it make more sense to call the last and first ones COUNTER_ENABLE_EVENTS_IOCTL and COUNTER_DISABLE_EVENTS_IOCTL? In any case, more explanation would be helpful. * COUNTER_ADD_WATCH_IOCTL: Queues a Counter watch for the specified event. The queued watches will not be applied until COUNTER_ENABLE_EVENTS_IOCTL is called. * COUNTER_ENABLE_EVENTS_IOCTL: Enables monitoring the events specified by the Counter watches that were queued by COUNTER_ADD_WATCH_IOCTL. If events are already enabled, the new set of watches replaces the old one. Calling this ioctl also has the effect of clearing the queue of watches added by COUNTER_ADD_WATCH_IOCTL. * COUNTER_DISABLE_EVENTS_IOCTL: Stops monitoring the previously enabled events. > + > +To configure events to gather Counter data, users first populate a > +`struct counter_watch` with the relevant event id, event channel id, and > +the information for the desired Counter component from which to read, > +and then pass it via the `COUNTER_ADD_WATCH_IOCTL` ioctl command. for restructured text, two backticks are needed for ``code`` formatting
diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter index 1820ce2f9183..8f6ea0a50b75 100644 --- a/Documentation/ABI/testing/sysfs-bus-counter +++ b/Documentation/ABI/testing/sysfs-bus-counter @@ -99,6 +99,15 @@ Description: Read-only attribute that indicates whether excessive noise is present at the channel Y counter inputs. +What: /sys/bus/counter/devices/counterX/countY/extensionZ_name +What: /sys/bus/counter/devices/counterX/extensionZ_name +What: /sys/bus/counter/devices/counterX/signalY/extensionZ_name +KernelVersion: 5.12 +Contact: linux-iio@vger.kernel.org +Description: + Read-only attribute that indicates the component name of + Extension Z. + What: /sys/bus/counter/devices/counterX/countY/function KernelVersion: 5.2 Contact: linux-iio@vger.kernel.org diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst index b842ddbbd8a0..4775dcaff557 100644 --- a/Documentation/driver-api/generic-counter.rst +++ b/Documentation/driver-api/generic-counter.rst @@ -223,19 +223,6 @@ whether an input line is differential or single-ended) and instead focus on the core idea of what the data and process represent (e.g. position as interpreted from quadrature encoding data). -Userspace Interface -=================== - -Several sysfs attributes are generated by the Generic Counter interface, -and reside under the /sys/bus/counter/devices/counterX directory, where -counterX refers to the respective counter device. Please see -Documentation/ABI/testing/sysfs-bus-counter for detailed -information on each Generic Counter interface sysfs attribute. - -Through these sysfs attributes, programs and scripts may interact with -the Generic Counter paradigm Counts, Signals, and Synapses of respective -counter devices. - Driver API ========== @@ -387,16 +374,16 @@ userspace interface components:: / driver callbacks / ------------------- | - +---------------+ - | - V - +--------------------+ - | Counter sysfs | - +--------------------+ - | Translates to the | - | standard Counter | - | sysfs output | - +--------------------+ + +---------------+---------------+ + | | + V V + +--------------------+ +---------------------+ + | Counter sysfs | | Counter chrdev | + +--------------------+ +---------------------+ + | Translates to the | | Translates to the | + | standard Counter | | standard Counter | + | sysfs output | | character device | + +--------------------+ +---------------------+ Thereafter, data can be transferred directly between the Counter device driver and Counter userspace interface:: @@ -427,23 +414,30 @@ driver and Counter userspace interface:: / u64 / ---------- | - +---------------+ - | - V - +--------------------+ - | Counter sysfs | - +--------------------+ - | Translates to the | - | standard Counter | - | sysfs output | - |--------------------| - | Type: const char * | - | Value: "42" | - +--------------------+ - | - --------------- - / const char * / - --------------- + +---------------+---------------+ + | | + V V + +--------------------+ +---------------------+ + | Counter sysfs | | Counter chrdev | + +--------------------+ +---------------------+ + | Translates to the | | Translates to the | + | standard Counter | | standard Counter | + | sysfs output | | character device | + |--------------------| |---------------------| + | Type: const char * | | Type: u64 | + | Value: "42" | | Value: 42 | + +--------------------+ +---------------------+ + | | + --------------- ----------------------- + / const char * / / struct counter_event / + --------------- ----------------------- + | | + | V + | +-----------+ + | | read | + | +-----------+ + | \ Count: 42 / + | ----------- | V +--------------------------------------------------+ @@ -452,7 +446,7 @@ driver and Counter userspace interface:: \ Count: "42" / -------------------------------------------------- -There are three primary components involved: +There are four primary components involved: Counter device driver --------------------- @@ -472,3 +466,163 @@ 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. + +Counter chrdev +-------------- +Translates counter data to the standard Counter character device; data +is transferred via standard character device read calls, while Counter +events are configured via ioctl calls. + +Sysfs Interface +=============== + +Several sysfs attributes are generated by the Generic Counter interface, +and reside under the `/sys/bus/counter/devices/counterX` directory, +where `X` is to the respective counter device id. Please see +`Documentation/ABI/testing/sysfs-bus-counter` for detailed information +on each Generic Counter interface sysfs attribute. + +Through these sysfs attributes, programs and scripts may interact with +the Generic Counter paradigm Counts, Signals, and Synapses of respective +counter devices. + +Counter Character Device +======================== + +Counter character device nodes are created under the `/dev` directory as +`counterX`, where `X` is the respective counter device id. Defines for +the standard Counter data types are exposed via the userspace +`include/uapi/linux/counter.h` file. + +Counter events +-------------- +Counter device drivers can support Counter events by utilizing the +`counter_push_event` function:: + + int counter_push_event(struct counter_device *const counter, const u8 event, + const u8 channel); + +The event id is specified by the `event` parameter; the event channel id +is specified by the `channel` parameter. When this function is called, +the Counter data associated with the respective event is gathered, and a +`struct counter_event` is generated for each datum and pushed to +userspace. + +Counter events can be configured by users to report various Counter +data of interest. This can be conceptualized as a list of Counter +component read calls to perform. For example:: + + +~~~~~~~~~~~~~~~~~~~~~~~~+~~~~~~~~~~~~~~~~~~~~~~~~+ + | COUNTER_EVENT_OVERFLOW | COUNTER_EVENT_INDEX | + +~~~~~~~~~~~~~~~~~~~~~~~~+~~~~~~~~~~~~~~~~~~~~~~~~+ + | Channel 0 | Channel 0 | + +------------------------+------------------------+ + | * Count 0 | * Signal 0 | + | * Count 1 | * Signal 0 Extension 0 | + | * Signal 3 | * Extension 4 | + | * Count 4 Extension 2 +------------------------+ + | * Signal 5 Extension 0 | Channel 1 | + | +------------------------+ + | | * Signal 4 | + | | * Signal 4 Extension 0 | + | | * Count 7 | + +------------------------+------------------------+ + +When `counter_push_event(counter, COUNTER_EVENT_INDEX, 1)` is called for +example, it will go down the list for the `COUNTER_EVENT_INDEX` event +channel 1 and execute the read callbacks for Signal 4, Signal 4 +Extension 0, and Count 4 -- the data returned for each is pushed to a +kfifo as a `struct counter_event`, which userspace can retrieve via a +standard read operation on the respective character device node. + +Userspace +--------- +Userspace applications can configure Counter events via ioctl operations +on the Counter character device node. There following ioctl codes are +supported and provided by the `linux/counter.h` userspace header file: + +* COUNTER_CLEAR_WATCHES_IOCTL: + Clear all Counter watches from all events + +* COUNTER_ADD_WATCH_IOCTL: + Add a Counter watch for the specified event + +* COUNTER_LOAD_WATCHES_IOCTL: + Activates the Counter watches added earlier + +To configure events to gather Counter data, users first populate a +`struct counter_watch` with the relevant event id, event channel id, and +the information for the desired Counter component from which to read, +and then pass it via the `COUNTER_ADD_WATCH_IOCTL` ioctl command. + +Note that an event can be watched without gathering Counter data by +setting the `component.type` member equal to `COUNTER_COMPONENT_NONE`. +With this configuration the Counter character device will simply +populate the event timestamps for those respective +`struct counter_event` elements and ignore the component value. + +The `COUNTER_ADD_WATCH_IOCTL` command will buffer these Counter watches. +When ready, the `COUNTER_LOAD_WATCHES_IOCTL` ioctl command may be used +to activate these Counter watches. + +Userspace applications can then execute a `read` operation (optionally +calling `poll` first) on the Counter character device node to retrieve +`struct counter_event` elements with the desired data. + +For example, the following userspace code opens `/dev/counter0`, +configures the `COUNTER_EVENT_INDEX` event channel 0 to gather Count 0 +and Count 1, and prints out the data as it becomes available on the +character device node:: + + #include <fcntl.h> + #include <linux/counter.h> + #include <stdio.h> + #include <string.h> + #include <sys/ioctl.h> + #include <unistd.h> + + struct counter_watch watches[2] = { + { + .component.type = COUNTER_COMPONENT_COUNT, + .component.scope = COUNTER_SCOPE_COUNT, + .component.parent = 0, + .event = COUNTER_EVENT_INDEX, + .channel = 0, + }, + { + .component.type = COUNTER_COMPONENT_COUNT, + .component.scope = COUNTER_SCOPE_COUNT, + .component.parent = 1, + .event = COUNTER_EVENT_INDEX, + .channel = 0, + }, + }; + + int main(void) + { + int fd; + struct counter_event event_data[2]; + + fd = open("/dev/counter0", O_RDWR); + + ioctl(fd, COUNTER_ADD_WATCH_IOCTL, watches); + ioctl(fd, COUNTER_ADD_WATCH_IOCTL, watches + 1); + ioctl(fd, COUNTER_LOAD_WATCHES_IOCTL); + + for (;;) { + read(fd, event_data, sizeof(event_data)); + + printf("Timestamp 0: %llu\tCount 0: %llu\n" + "Error Message 0: %s\n" + "Timestamp 1: %llu\tCount 1: %llu\n" + "Error Message 1: %s\n", + (unsigned long long)event_data[0].timestamp, + (unsigned long long)event_data[0].value, + strerror(event_data[0].errno), + (unsigned long long)event_data[1].timestamp, + (unsigned long long)event_data[1].value, + strerror(event_data[1].errno)); + } + + return 0; + } diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst index 55a2d9b2ce33..b7761ceb82a7 100644 --- a/Documentation/userspace-api/ioctl/ioctl-number.rst +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst @@ -88,6 +88,7 @@ Code Seq# Include File Comments <http://infiniband.sourceforge.net/> 0x20 all drivers/cdrom/cm206.h 0x22 all scsi/sg.h +0x3E 00-0F linux/counter.h <mailto:linux-iio@vger.kernel.org> '!' 00-1F uapi/linux/seccomp.h '#' 00-3F IEEE 1394 Subsystem Block for the entire subsystem
This patch adds high-level documentation about the Counter subsystem character device interface. Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com> --- Documentation/ABI/testing/sysfs-bus-counter | 9 + Documentation/driver-api/generic-counter.rst | 236 +++++++++++++++--- .../userspace-api/ioctl/ioctl-number.rst | 1 + 3 files changed, 205 insertions(+), 41 deletions(-)