From patchwork Wed Sep 29 03:16:00 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: William Breathitt Gray X-Patchwork-Id: 12524471 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BBB10C433F5 for ; Wed, 29 Sep 2021 03:16:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A131861381 for ; Wed, 29 Sep 2021 03:16:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243921AbhI2DSb (ORCPT ); Tue, 28 Sep 2021 23:18:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59552 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243905AbhI2DS1 (ORCPT ); Tue, 28 Sep 2021 23:18:27 -0400 Received: from mail-pg1-x530.google.com (mail-pg1-x530.google.com [IPv6:2607:f8b0:4864:20::530]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 37F76C061745; Tue, 28 Sep 2021 20:16:47 -0700 (PDT) Received: by mail-pg1-x530.google.com with SMTP id 66so833879pgc.9; Tue, 28 Sep 2021 20:16:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=Q7EGeGlc3g3UDIDbbGLhO2X3OU7aZNwWkPtPyvxo14g=; b=HIflXNzE7mxlzeV4yFMuZX5F07sLBnNoIKi8a/rRfloVqlVQVWWesr9bfm9BnvIjDt pyU5WQGSMmcuZZrInUp3boMx1xkyiRCQpzzorNWkHbXjp3rv6myy4UghuucsUsZ9/nw1 PVSYor88fqVNATEGW5Ar3MnAqP5PDsu2Cr0Rmeg74JewERvAd7FXYc3Yp1Cc+NQqnGVb ur01oKcIGg5QjolmiHey8DxhYEvPe6ykeFerzpBQIgKWKg97piG/zPnTJfdZV98LNZDw mGU6ypIu2RPc7gCUPtWyZ9lW5jdkNeiVV/tsXtexg2AuLiXO40IzO1uoBjfa5FXCQbBa fjhQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Q7EGeGlc3g3UDIDbbGLhO2X3OU7aZNwWkPtPyvxo14g=; b=pSXUjjEmEtgE1lIV+GphwQ8sYalH+/+UQs0pvtzWJGE9W1V2VxcR9SE1WLlPg+s1zL NQVSWDfj9UrN+tXd2Bx5quRiCQb5ZoNn8uMTpe6mk4mJkyUmGBJtm/Osc1jfyO3lrgw/ bXkjEWxNHgLe5EKsPowTJN1NW6Z0lpRNaxhGvBPyMaSlmKFg9pFduloj6P8uqZ26tYy/ sHIbEUN5+RKoJKvtKpj/OuE+pZ0Q5A3l6nc3hbI0CJH8OWsin9r5eMUPDk8P43Hw0mi5 xO50H3JFAw9Omv8Ejl/dKsjXZwwtQhKQl5rjv3nJGHjniVxYWH+PRLW+J2NW01aLtg6k 3XNg== X-Gm-Message-State: AOAM532gyB3C1c905xgpR8tqH/MWaUkZmtZHWDZiuLkdBKZhOGSPYXZI WzLwbwXHIxGnO2Yx183vK78= X-Google-Smtp-Source: ABdhPJxlqipwJQ9qpSdLdWR9vR8UgL2mudNzS6+cjswPnvyZWupMp/FSYK5Kka7xTZSmzhdeJKtKcQ== X-Received: by 2002:aa7:9485:0:b0:44b:b7ff:85bd with SMTP id z5-20020aa79485000000b0044bb7ff85bdmr4603057pfk.20.1632885406703; Tue, 28 Sep 2021 20:16:46 -0700 (PDT) Received: from localhost.localdomain ([156.146.35.76]) by smtp.gmail.com with ESMTPSA id 65sm464203pfv.210.2021.09.28.20.16.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Sep 2021 20:16:46 -0700 (PDT) From: William Breathitt Gray 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 Subject: [PATCH v17 3/9] docs: counter: Document character device interface Date: Wed, 29 Sep 2021 12:16:00 +0900 Message-Id: <7a71dff2868195901d074ae2ec1b5611838d4b24.1632884256.git.vilhelm.gray@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-iio@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 | 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..25932dcb6e67 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 events 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 7 -- 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 2e8134059c87..0ba463be6c58 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