From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.0 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_SIGNED,DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C589BC433E6 for ; Tue, 21 Jul 2020 19:38:05 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 835CB206C1 for ; Tue, 21 Jul 2020 19:38:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="vuqSctd/"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="LswHUBdq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 835CB206C1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-Id:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=VGSWl6Y4gli4VD2I34o+xmAvI0ylilz/gHfQJsfTjhA=; b=vuqSctd/XLzTY8toEwBP/8DLh e2lPDaU83Si1Bcic+pWWcSzxOi1iUE/mupHtBY035mVam3UMJ5EK7nZ3bqsmPsIfMF8nccCE73zaJ nVrnr+MBWgZhDjhROOF1ke1siPfIE6yDrpsKLLdSRDKphIxzwaF+R+TuWuLRrH7D0M7DHxBj5Aza3 TBVIn2ny65M6MK408Bj8ybpEmkwlPoDTqksIhDKQygrPm8TVjSxyyaLCirT2tGkdseX6XVCHCmCyd lpkD6S8uOpzVsq5txj8OPAje3GPBc2TrdoFZ17/VMt9BAZE1YbmSm3CgSix9O5VW18ILNuOybTNko SowTrwvYA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jxy3p-00014W-Mt; Tue, 21 Jul 2020 19:36:21 +0000 Received: from mail-qk1-x744.google.com ([2607:f8b0:4864:20::744]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jxy3h-00012R-QV for linux-arm-kernel@lists.infradead.org; Tue, 21 Jul 2020 19:36:16 +0000 Received: by mail-qk1-x744.google.com with SMTP id z15so13800762qki.10 for ; Tue, 21 Jul 2020 12:36:13 -0700 (PDT) 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=EkmSpmhEZ7Vcfm2rjya4j142Ah+gIfxqSabZ9X2+OQk=; b=LswHUBdqdFDzDoWaN5hiGPSzeG14JPwzq5oiZbcopOsfAfQMECrJZoYvZRJk3vRVS+ IYnOa4FQgrC/ATGbjm+TpIJuyS8RXAJKuHFY8Fb8+72i6psvcjb8eP7Et36GzODXUkFj G0B17T1ZD0IiV4Wuv4B2/XhDp3HB7qCi1tSm6mGmLWS/cX1ZcP33wDYxCwUGUcc0PfJT 9hMhon0UZc0himDV8vSG2Yjzu9adZg6HDeDA0jmV+RRaOJ1mw7Ek8U9ve9NogXebsMY8 k+DQoItLyq+3pisZeiVnKmDYPvBZoa/nvBhIMuX8KyjfoOsMJZ4xGXjx0W8dL9D46TFE F+sA== 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=EkmSpmhEZ7Vcfm2rjya4j142Ah+gIfxqSabZ9X2+OQk=; b=pX41ReFijd04oRu53gMfw2c5N7g1dcOmCdRQK//6hiXCKtkT3+xOAffuP7NnIFr7q3 oqnaOha7iGhvR7uqPxBVe1iQ/LqmIwlCJIVmHoXBQ/tqekpbQAcDMfv39AK6AlgxrEtc GYig7T94PdI7E5t6qHfWGbyS4KpBNJElwBTEOf75MDli9Bjpkce1hYUfbGGJWYsQuD34 gd9kuzZH/Gjez6FcjR1a8V+/Uw2S5YlwdujSpUO+1ogDy8SWdy/8vDm8pI407zf8Q+43 ZZ+F1hbciMUIzR4WMh20BawJmVMtETtoc+6c7yZHcpLttGBlV9E7GzTEBYduiXSt6tn2 uoXw== X-Gm-Message-State: AOAM530dOHbYeN/AZtA7ZVldXm/wdKRp7/SkNNmGTAos5/Xi/WHY4HKy IKJAUApwWc5ydY+8B4gwrRc= X-Google-Smtp-Source: ABdhPJzWz1aEsBaigm4673xyKRgmVwtNkd72PAJG1KG5LD9K3GN8e60qf7VA+P4ubw/TBm4D726Kvg== X-Received: by 2002:ae9:dcc6:: with SMTP id q189mr29931803qkf.332.1595360172014; Tue, 21 Jul 2020 12:36:12 -0700 (PDT) Received: from localhost.localdomain (072-189-064-225.res.spectrum.com. [72.189.64.225]) by smtp.gmail.com with ESMTPSA id j72sm3331351qke.20.2020.07.21.12.36.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Jul 2020 12:36:11 -0700 (PDT) From: William Breathitt Gray To: jic23@kernel.org Subject: [PATCH v4 2/5] docs: counter: Update to reflect sysfs internalization Date: Tue, 21 Jul 2020 15:35:48 -0400 Message-Id: <79e05c620129b35317684e8ef4e573bce531570d.1595358237.git.vilhelm.gray@gmail.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: References: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200721_153614_018697_EE9CBCB0 X-CRM114-Status: GOOD ( 22.90 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kamel.bouhara@bootlin.com, gwendal@chromium.org, david@lechnology.com, linux-iio@vger.kernel.org, patrick.havelange@essensium.com, alexandre.belloni@bootlin.com, linux-kernel@vger.kernel.org, mcoquelin.stm32@gmail.com, William Breathitt Gray , fabrice.gasnier@st.com, syednwaris@gmail.com, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, alexandre.torgue@st.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 --- Documentation/driver-api/generic-counter.rst | 216 +++++++++++++------ 1 file changed, 150 insertions(+), 66 deletions(-) diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst index b02c52cd69d6..fa2d699d44a5 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_data 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_DATA_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_data count_ext[] = { + COUNTER_DATA_DIRECTION(count_direction_read), + COUNTER_DATA_ENABLE(count_enable_read, count_enable_write), + COUNTER_DATA_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_data 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 +347,102 @@ 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:: + + Count data request: + ~~~~~~~~~~~~~~~~~~~ + ---------------------- + / Counter device \ + +----------------------+ + | Count register: 0x28 | + +----------------------+ + | + ----------------- + / raw count data / + ----------------- + | + V + +----------------------------+ + | Counter device driver |----------+ + +----------------------------+ | + | Processes data from device | ------------------- + |----------------------------| / driver callbacks / + | Type: u64 | ------------------- + | Value: 42 | | + +----------------------------+ | + | | + ---------- | + / u64 / | + ---------- | + | | + | V + | +----------------------+ + | | Counter core | + | +----------------------+ + | | Routes device driver | + | | callbacks to the | + | | userspace interfaces | + | +----------------------+ + | | + | ------------------- + | / driver callbacks / + | ------------------- + | | + +-------+ | + | | + | +---------------+ + | | + 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. -- 2.27.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel