From: William Breathitt Gray <vilhelm.gray@gmail.com>
To: jic23@kernel.org
Cc: linux-stm32@st-md-mailman.stormreply.com, kernel@pengutronix.de,
a.fatoum@pengutronix.de, kamel.bouhara@bootlin.com,
gwendal@chromium.org, alexandre.belloni@bootlin.com,
david@lechnology.com, linux-iio@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, syednwaris@gmail.com,
patrick.havelange@essensium.com, fabrice.gasnier@st.com,
mcoquelin.stm32@gmail.com, alexandre.torgue@st.com,
o.rempel@pengutronix.de, jarkko.nikula@linux.intel.com,
William Breathitt Gray <vilhelm.gray@gmail.com>
Subject: [PATCH v14 11/17] docs: counter: Document character device interface
Date: Tue, 3 Aug 2021 21:06:21 +0900 [thread overview]
Message-ID: <b8457d92a74fb25d7c0beb769fc9c8c04a9eb3d1.1627990337.git.vilhelm.gray@gmail.com> (raw)
In-Reply-To: <cover.1627990337.git.vilhelm.gray@gmail.com>
This patch adds high-level documentation about the Counter subsystem
character device interface.
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
Documentation/driver-api/generic-counter.rst | 177 ++++++++++++++----
.../userspace-api/ioctl/ioctl-number.rst | 1 +
2 files changed, 137 insertions(+), 41 deletions(-)
diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst
index f6397218aa4c..e9cb95c1c828 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
==========
@@ -388,16 +375,16 @@ 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::
@@ -428,23 +415,30 @@ 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
+--------------------------------------------------+
@@ -453,7 +447,7 @@ driver and Counter userspace interface::
\ Count: "42" /
--------------------------------------------------
-There are three primary components involved:
+There are four primary components involved:
Counter device driver
---------------------
@@ -473,3 +467,104 @@ 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::
+
+ void 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:
+
+* :c:macro:`COUNTER_ADD_WATCH_IOCTL`
+
+* :c:macro:`COUNTER_ENABLE_EVENTS_IOCTL`
+
+* :c:macro:`COUNTER_DISABLE_EVENTS_IOCTL`
+
+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_ENABLE_EVENTS_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.
diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
index 1409e40e6345..fc4ccc79b1b8 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
--
2.32.0
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-08-03 12:25 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-03 12:06 [PATCH v14 00/17] Introduce the Counter character device interface William Breathitt Gray
2021-08-03 12:06 ` [PATCH v14 01/17] counter: 104-quad-8: Return error when invalid mode during ceiling_write William Breathitt Gray
2021-08-08 17:06 ` Jonathan Cameron
2021-08-03 12:06 ` [PATCH v14 02/17] counter: Return error code on invalid modes William Breathitt Gray
2021-08-08 17:07 ` Jonathan Cameron
2021-08-03 12:06 ` [PATCH v14 03/17] counter: Standardize to ERANGE for limit exceeded errors William Breathitt Gray
2021-08-08 17:08 ` Jonathan Cameron
2021-08-03 12:06 ` [PATCH v14 04/17] counter: Rename counter_signal_value to counter_signal_level William Breathitt Gray
2021-08-08 17:10 ` Jonathan Cameron
2021-08-03 12:06 ` [PATCH v14 05/17] counter: Rename counter_count_function to counter_function William Breathitt Gray
2021-08-08 17:15 ` Jonathan Cameron
2021-08-03 12:06 ` [PATCH v14 07/17] counter: Update counter.h comments to reflect sysfs internalization William Breathitt Gray
2021-08-03 12:06 ` [PATCH v14 08/17] docs: counter: Update " William Breathitt Gray
2021-08-03 12:06 ` [PATCH v14 09/17] counter: Move counter enums to uapi header William Breathitt Gray
2021-08-03 12:06 ` [PATCH v14 10/17] counter: Add character device interface William Breathitt Gray
2021-08-03 12:06 ` William Breathitt Gray [this message]
2021-08-03 12:06 ` [PATCH v14 12/17] tools/counter: Create Counter tools William Breathitt Gray
2021-08-03 12:06 ` [PATCH v14 13/17] counter: Implement signalZ_action_component_id sysfs attribute William Breathitt Gray
2021-08-03 12:06 ` [PATCH v14 14/17] counter: Implement *_component_id sysfs attributes William Breathitt Gray
2021-08-03 12:06 ` [PATCH v14 15/17] counter: Implement events_queue_size sysfs attribute William Breathitt Gray
2021-08-03 12:06 ` [PATCH v14 16/17] counter: 104-quad-8: Replace mutex with spinlock William Breathitt Gray
2021-08-03 12:06 ` [PATCH v14 17/17] counter: 104-quad-8: Add IRQ support for the ACCES 104-QUAD-8 William Breathitt Gray
[not found] ` <2df092636a9eea5a3ddae1e9a6429e32b51284f7.1627990337.git.vilhelm.gray@gmail.com>
[not found] ` <20210808182325.2620de00@jic23-huawei>
2021-08-09 3:59 ` [PATCH v14 06/17] counter: Internalize sysfs interface code William Breathitt Gray
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