Received: by 2002:a05:6a10:8c0a:0:0:0:0 with SMTP id go10csp2895010pxb; Fri, 12 Feb 2021 04:21:52 -0800 (PST) X-Google-Smtp-Source: ABdhPJzC+AoJWke04CNYTje3InBk5kmJBnCmUA6pE7jeu/IlvAZ23PN46HGw6CvJ3wpjKGm1Qr8Y X-Received: by 2002:aa7:d283:: with SMTP id w3mr2145579edq.30.1613132511919; Fri, 12 Feb 2021 04:21:51 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1613132511; cv=none; d=google.com; s=arc-20160816; b=TnOKE/nkjHGkjeB8Jzek2+HDpZ7a33kTkNiUBBGCNbmrgMrB2CPV8Kjha1TGAIOX5b bDvEtE0EOSeAm1jsa+ZozztPEicTU1PYYR7jGIivHljlL8jFBPf7USucwMgwab9xYx2N OHwY2mNNJ660ruWO+hOPyLyMuc5C7iadRZxFUV7V5EJPXfgUcmLf//s3SbHW8TAym2OH MTpeS+LZdhiepc/XlPDjQsdNH0gnjXqTi7lprhNUTPJVwZgDUb+Qg0uOT9cxF0xW1ji6 TyTENJfycCMOA1lQEkvE2vuyX555Ox63V+GnPGe1NbQzA6xRukLWQokT6EPzY7nYQfsw QMLw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=bQhX7bICYYa9oeO9vYn1va8mpc8PCr4E8fj9/wIde94=; b=IFHjXTtCV5XLVKhmXKGOFKPvMOsYWHvrtkV8rblq9C4ZMcVh34UX1V0mcvwMhtyLno bOWwhvVvuy1h0lw+lAGNI9xhXUH9QiGxdbTQUCkoCFFQGniAHsP1cqTxGX08lmpD05vc zJClUuts3757Ues5tIY2t6utdvmqVKKt6XEBSaRspr4+ep4jTfJJPTsLpo0c6ctuE9I0 1EGlRih+izkRGjvlTlPcTk5Aq0nMwww72lOTZCRRsJe73oE3w+xNIoS40nxVy4O9gcrv JIotxucjiBawSG8yCxMmnqTMnhxrYoIpgOXi5f5IcSgwm8ZowTMF36f2yG8Jrjqg+N9a 0KhQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b="Iv/BnV+f"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id x20si6076528ejw.92.2021.02.12.04.21.28; Fri, 12 Feb 2021 04:21:51 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b="Iv/BnV+f"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231236AbhBLMUq (ORCPT + 99 others); Fri, 12 Feb 2021 07:20:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37646 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231383AbhBLMQ2 (ORCPT ); Fri, 12 Feb 2021 07:16:28 -0500 Received: from mail-qt1-x834.google.com (mail-qt1-x834.google.com [IPv6:2607:f8b0:4864:20::834]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E7794C06178B; Fri, 12 Feb 2021 04:15:47 -0800 (PST) Received: by mail-qt1-x834.google.com with SMTP id h16so6453277qth.11; Fri, 12 Feb 2021 04:15:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=bQhX7bICYYa9oeO9vYn1va8mpc8PCr4E8fj9/wIde94=; b=Iv/BnV+fLWSQsizXdeoZwLqkV/fc4wANewmb/MFZKVaVvheRsffpkrydkhaSctsFlo YQlwzGmIN44wd/RiU6LK1WQufYeyRWHCDikgrVtdqzfjUkYMnONl5SVR0bFuVkc0Ogxn 4XL8YMo0wL0YuUJp+SNutCcZe2ZdiZRIiN2cUaoLO9ZEaJLePW+WMLAG07QHHr5ncH7v g9RdP4694I72kKJmFsOzuF4YIM+5Vqy0NHRGWzkw97mNQ145xHmoB3UMbgf0FXVy1CEF rsApSgumep95ZbX7ucRTgHudp3v7T0CLEHZvRVK+RMBvQ+kYiuJnJN+JT9BK6zIjMpsr ZF/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=bQhX7bICYYa9oeO9vYn1va8mpc8PCr4E8fj9/wIde94=; b=nZwdwrUYi5o+X4L6hbUUzGPgSVY4ZZCaTR3dTzoY+2f6+1MrdfQymAbF7evvBLcyQ+ QAe9RmYCuHK0UOY5cveARYtEdElKmxL0aAKEowIkAgHuVQTskXBiZsrPw6dE58xDG38x 6wJ0hK8G0XfK6urwxEAtgixwGukBKLM9O5NkpZGFUpzetBjKtF5RO7YtDXIAkLGP96qb FHc1XVQSOlBynZTXQl/VTvXh9TX9cY6RpPMAj62OsCj3AG12gaXCrTZRL1ssBCctGFXR y18F91Z3jm9OJY53eNMNQS8IO+7kvBhRncengRmaoTOjDfqzumMkyWl2ESJ6hzLXcS2G jzJg== X-Gm-Message-State: AOAM5304w8XgYxKcMitiiU2E9nUP0kAOOi5PmQE9cIo815E7jlaRbIHK A/kc+SMZ5Q9fNuKOq4/b6wA= X-Received: by 2002:ac8:47da:: with SMTP id d26mr2026024qtr.28.1613132147148; Fri, 12 Feb 2021 04:15:47 -0800 (PST) Received: from localhost.localdomain ([193.27.12.132]) by smtp.gmail.com with ESMTPSA id y135sm6278534qkb.14.2021.02.12.04.15.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Feb 2021 04:15:46 -0800 (PST) From: William Breathitt Gray To: jic23@kernel.org Cc: kernel@pengutronix.de, linux-stm32@st-md-mailman.stormreply.com, 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, William Breathitt Gray Subject: [PATCH v8 18/22] docs: counter: Document character device interface Date: Fri, 12 Feb 2021 21:13:42 +0900 Message-Id: <350cafba81d3220b64efdb019bd76c08eb1e5d10.1613131238.git.vilhelm.gray@gmail.com> X-Mailer: git-send-email 2.30.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch adds high-level documentation about the Counter subsystem character device interface. Signed-off-by: William Breathitt Gray --- Documentation/driver-api/generic-counter.rst | 243 +++++++++++++++--- .../userspace-api/ioctl/ioctl-number.rst | 1 + 2 files changed, 203 insertions(+), 41 deletions(-) diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst index f6397218aa4c..3be109dc81bb 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 +467,170 @@ 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: + +* 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. + +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. + +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 + #include + #include + #include + #include + #include + + 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_ENABLE_EVENTS_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].status), + (unsigned long long)event_data[1].timestamp, + (unsigned long long)event_data[1].value, + strerror(event_data[1].status)); + } + + return 0; + } diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst index a4c75a28c839..8ddca931ec4e 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 0x20 all drivers/cdrom/cm206.h 0x22 all scsi/sg.h +0x3E 00-0F linux/counter.h '!' 00-1F uapi/linux/seccomp.h '#' 00-3F IEEE 1394 Subsystem Block for the entire subsystem -- 2.30.0