From patchwork Thu Feb 8 10:01:25 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ramona Gradinariu X-Patchwork-Id: 198269 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a05:7300:50ea:b0:106:860b:bbdd with SMTP id r10csp62277dyd; Thu, 8 Feb 2024 02:07:59 -0800 (PST) X-Forwarded-Encrypted: i=3; AJvYcCURcO2mnd5VMXm2LrsGOKKw3gwvx6HOqcUF3F3GOg/djm7kZL+TDes4EwT4KGKPkknFb9JwURSVIo2aM/f+q5Zj8f+sqw== X-Google-Smtp-Source: AGHT+IGGQLDLlCYOE4PLR1E7bvxauou5lX7cFt8kEux3fNbssvhfq/3Po5f0GDt7pe2KDneYBzmU X-Received: by 2002:a05:620a:6285:b0:785:a41b:8247 with SMTP id ov5-20020a05620a628500b00785a41b8247mr2703573qkn.33.1707386879571; Thu, 08 Feb 2024 02:07:59 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1707386879; cv=pass; d=google.com; s=arc-20160816; b=s0G427+6qumWQoJmo2XUoN+TVeMzqq3wnUZE897GeH5ib9K1zZaxoGo8//0tKxwn/t Xiftlb2DG/2cNhUxQXgqizZxGDR58ItTUKsg0+/oTHOCmzHqus/zU8wR9ViDjjnyDcgy H1y4GJ072M6qFWC6xyfps1TlN/0vaZcAT1pRoo2KbA11pa0aT5AGomARsEMF+Y5sfjCi 29gaLr9fVnCXvprw9/d0s8cxd5SMEadEfWzfHMK6MuEne80zRPOkIdCKg1fipX3mvr69 BdeOiZGruNdKMqHqC9dO8YmfqwDWV3ZL7KXQS6QLwPCwsIOrKB4OsJuRGxH5cA4BGVSC 88Lw== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:list-unsubscribe :list-subscribe:list-id:precedence:references:in-reply-to:message-id :date:subject:cc:to:from:dkim-signature; bh=JcIOnqV+xnvEiy7Tt/3i5INlsQIUUxMJjPkdq0ILnBk=; fh=qn76+4p4Uf9TR1ok/e0kDr3jEQRo+/jHcr27z1HhAGc=; b=EstqDaJ7LtdWo30NypfVyg5/wRXVhC8hoy4QuJYCFWSqdOnJRO9WEhb8LC4UHw1z0e w7FI18WpUHzMqX1oRur1xOt5KIjMLjRDSGqjw4+KgGDGuZvTU0Tk9pxtCmAxuiUbqXg8 9ikFWs3GtDY3RNKI7n4YtT75GDELjoQz0Tg2XLUfVjS7KsqevGssLM04Xh8lh3BJMo/a 4MYjCjf8MCkRCwQWczaeaweCyNJyYDqFjWiIycdM/wPLEHOwa0qMeJK7yq6+Vet6JE70 QYgvHTmoQbrcHiLkm5/IWtWm/NZB2xRRJMqQpcc8U/krUYTvf0P0B3HjFxKgqdAB6A06 RBtg==; dara=google.com ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@analog.com header.s=DKIM header.b=HNEusqfJ; arc=pass (i=1 spf=pass spfdomain=analog.com dkim=pass dkdomain=analog.com dmarc=pass fromdomain=analog.com); spf=pass (google.com: domain of linux-kernel+bounces-57818-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-57818-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=analog.com X-Forwarded-Encrypted: i=2; AJvYcCVlDTFMVtwq/A5onrwFtbFl3i3K2mPIBGW5shiphZfz0473PaxHvtBdMeyVqxC28a+GdONoPosf+/NYriKUBSZnqvCABQ== Received: from ny.mirrors.kernel.org (ny.mirrors.kernel.org. [2604:1380:45d1:ec00::1]) by mx.google.com with ESMTPS id d20-20020a05620a137400b00783df78822bsi2960570qkl.114.2024.02.08.02.07.59 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Feb 2024 02:07:59 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-57818-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1; Authentication-Results: mx.google.com; dkim=pass header.i=@analog.com header.s=DKIM header.b=HNEusqfJ; arc=pass (i=1 spf=pass spfdomain=analog.com dkim=pass dkdomain=analog.com dmarc=pass fromdomain=analog.com); spf=pass (google.com: domain of linux-kernel+bounces-57818-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-57818-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=analog.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ny.mirrors.kernel.org (Postfix) with ESMTPS id 4D59A1C27F20 for ; Thu, 8 Feb 2024 10:07:59 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id DA3246BFC2; Thu, 8 Feb 2024 10:02:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=analog.com header.i=@analog.com header.b="HNEusqfJ" Received: from mx0b-00128a01.pphosted.com (mx0a-00128a01.pphosted.com [148.163.135.77]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B770D6EB6D; Thu, 8 Feb 2024 10:02:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.135.77 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707386537; cv=none; b=NRC6ekBHdyDjyq5GOkXzHNT7My/0z48X6ZUu3lk+Y9owofwj8dkuVDahVzheZyh1RIs0FSHjnUjgdaLezJFBLSk1D0DXq1sOtB/IdkWQjETowHr7Pm90gbz6VkC6ytKDENGyzo7tAerSpvvW058O5uu5V4u3oIyz/Sl8SQwp1cE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707386537; c=relaxed/simple; bh=0PMCCV5oxr328VLVSFyPIqEvIRppT6sRoYT0wHRHraM=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=L8A1gVA+ykBdNzxzbRtZds4MECiC8Lte53JgII1ISWU3+1UNeToxSS7P9E2tEE9p3gnwWJ5qr3ubbHiG7Tt9CfvlCLQ+IbzKiYWe2hPuFQkI0I3LPadc5H5aWeWTqDcdn0bjMFpmTbJMB1crJZ9XeMrvGDKWYwajnfvcSTU8TrQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=analog.com; spf=pass smtp.mailfrom=analog.com; dkim=pass (2048-bit key) header.d=analog.com header.i=@analog.com header.b=HNEusqfJ; arc=none smtp.client-ip=148.163.135.77 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=analog.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=analog.com Received: from pps.filterd (m0375855.ppops.net [127.0.0.1]) by mx0b-00128a01.pphosted.com (8.17.1.24/8.17.1.24) with ESMTP id 4187NSZ1001534; Thu, 8 Feb 2024 05:02:12 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=analog.com; h= from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding:content-type; s=DKIM; bh=JcIOnqV+xnvEiy7Tt/3i5INlsQIUUxMJjPkdq0ILnBk=; b=HNEusqfJA6WE izihZ4e4gu5yu9eU1BNi19jZp7wDUSs+g5IRJeYFtGODC9vPRSpXt8e8xmotL7hn ff6EKN8L9295QPyx/njS+++aMiI0/OEV6qV417H1TTXS4uFycUY5ipbHiuzf8x1S DFRrsJXTp91ttxvK9/xwqkJfgwqiw1+Ylm9YGMscpEWrEoLAaK/bqQqPHuWpS1jM h2LJrpBIm2x4CwMh0Eb7kTJjx57/bkQHvTrdvfWt+ZN3UmnRKOGSRD9AFjMZ50k2 POCrTRK3I9tU1OgrmPOBEbcYTcKUXR1PSwTUmONPCSeHxXo7FNX0vJE3IBGwV6TX TflYe2gNiQ== Received: from nwd2mta4.analog.com ([137.71.173.58]) by mx0b-00128a01.pphosted.com (PPS) with ESMTPS id 3w4thargq4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 08 Feb 2024 05:02:11 -0500 (EST) Received: from ASHBMBX9.ad.analog.com (ASHBMBX9.ad.analog.com [10.64.17.10]) by nwd2mta4.analog.com (8.14.7/8.14.7) with ESMTP id 418A2ASC053254 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 8 Feb 2024 05:02:10 -0500 Received: from ASHBCASHYB4.ad.analog.com (10.64.17.132) by ASHBMBX9.ad.analog.com (10.64.17.10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.14; Thu, 8 Feb 2024 05:02:09 -0500 Received: from ASHBMBX8.ad.analog.com (10.64.17.5) by ASHBCASHYB4.ad.analog.com (10.64.17.132) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.14; Thu, 8 Feb 2024 05:01:46 -0500 Received: from zeus.spd.analog.com (10.66.68.11) by ashbmbx8.ad.analog.com (10.64.17.5) with Microsoft SMTP Server id 15.2.986.14 via Frontend Transport; Thu, 8 Feb 2024 05:01:46 -0500 Received: from rbolboac.ad.analog.com ([10.48.65.135]) by zeus.spd.analog.com (8.15.1/8.15.1) with ESMTP id 418A1UNq027963; Thu, 8 Feb 2024 05:01:37 -0500 From: Ramona Gradinariu To: , , , , , CC: Ramona Gradinariu Subject: [PATCH v3 2/3] docs: iio: add documentation for device buffers Date: Thu, 8 Feb 2024 12:01:25 +0200 Message-ID: <20240208100126.183697-3-ramona.gradinariu@analog.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240208100126.183697-1-ramona.gradinariu@analog.com> References: <20240208100126.183697-1-ramona.gradinariu@analog.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ADIRuleOP-NewSCL: Rule Triggered X-Proofpoint-GUID: R-nWklM-ppIE-Yd6zW9gl-fA00Wl2Lzp X-Proofpoint-ORIG-GUID: R-nWklM-ppIE-Yd6zW9gl-fA00Wl2Lzp X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-02-08_01,2024-02-07_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxscore=0 suspectscore=0 bulkscore=0 malwarescore=0 adultscore=0 clxscore=1015 mlxlogscore=999 impostorscore=0 spamscore=0 phishscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2401310000 definitions=main-2402080052 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790324904758715873 X-GMAIL-MSGID: 1790324904758715873 Add documentation for IIO device buffers describing buffer attributes and how data is structured in buffers using scan elements. Signed-off-by: Ramona Gradinariu --- changes in v3: - new patch Documentation/iio/iio_devbuf.rst | 121 +++++++++++++++++++++++++++++++ Documentation/iio/index.rst | 1 + 2 files changed, 122 insertions(+) create mode 100644 Documentation/iio/iio_devbuf.rst -- 2.34.1 diff --git a/Documentation/iio/iio_devbuf.rst b/Documentation/iio/iio_devbuf.rst new file mode 100644 index 000000000000..0563b65316cb --- /dev/null +++ b/Documentation/iio/iio_devbuf.rst @@ -0,0 +1,121 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================= +Industrial IIO device buffers +============================= + +1. Overview +=========== + +The Industrial I/O core offers a way for continuous data capture based on a +trigger source. Multiple data channels can be read at once from +/dev/iio:deviceX character device node, thus reducing the CPU load. + +2. Buffer attributes +==================== + +An IIO buffer has an associated attributes directory under +/sys/bus/iio/iio:deviceX/buffer/. Here are some of the existing attributes: + +Length +------ + +Read / Write attribute which states the total number of data samples (capacity) +that can be stored by the buffer. + +Enable +------ + +Read / Write attribute which starts / stops the buffer capture. This file should +be written last, after length and selection of scan elements. + +Watermark +--------- + +Read / Write positive integer attribute specifying the maximum number of scan +elements to wait for. + +Poll will block until the watermark is reached. + +Blocking read will wait until the minimum between the requested read amount or +the low water mark is available. + +Non-blocking read will retrieve the available samples from the buffer even if +there are less samples then watermark level. This allows the application to +block on poll with a timeout and read the available samples after the timeout +expires and thus have a maximum delay guarantee. + +Data available +-------------- + +Read-only attribute indicating the bytes of data available in the buffer. In the +case of an output buffer, this indicates the amount of empty space available to +write data to. In the case of an input buffer, this indicates the amount of data +available for reading. + +3. Scan elements +================ + +The meta information associated with a channel reading placed in a buffer is +called a scan element. The important bits configuring scan elements are exposed +to userspace applications via the /sys/bus/iio/iio:deviceX/scan_elements/ +directory. This directory contains attributes of the following form: + +Enable +------ + +Read/ Write attribute used for enabling a channel. If and only if its value +is non zero, then a triggered capture will contain data samples for this +channel. + +Index +----- + +Read-only positive integer attribute specifying the position of the channel in +the buffer. Note these are not dependent on what is enabled and may not be +contiguous. Thus for user-space to establish the full layout these must be used +in conjunction with all _en attributes to establish which channels are present, +and the relevant _type attributes to establish the data storage format. + +Type +---- + +Read-only attribute containing the description of the scan element data storage +within the buffer and hence the form in which it is read from user space. Format +is [be|le]:[s|u]bits/storagebits[Xrepeat][>>shift], where: + +- **be** or **le** specifies big or little endian. +- **s** or **u**, specifies if signed (2's complement) or unsigned. +- **bits**, is the number of valid data bits. +- **storagebits**, is the number of bits (after padding) that it occupies in the + buffer. +- **repeat**, specifies the number of bits/storagebits repetitions. When the + repeat element is 0 or 1, then the repeat value is omitted. +- **shift**, if specified, is the shift that needs to be applied prior to + masking out unused bits. + +For example, a driver for a 3-axis accelerometer with 12 bit resolution where +data is stored in two 8-bits registers as follows: + +.. code-block:: bash + + 7 6 5 4 3 2 1 0 + +---+---+---+---+---+---+---+---+ + |D3 |D2 |D1 |D0 | X | X | X | X | (LOW byte, address 0x06) + +---+---+---+---+---+---+---+---+ + + 7 6 5 4 3 2 1 0 + +---+---+---+---+---+---+---+---+ + |D11|D10|D9 |D8 |D7 |D6 |D5 |D4 | (HIGH byte, address 0x07) + +---+---+---+---+---+---+---+---+ + +will have the following scan element type for each axis: + +.. code-block:: bash + + $ cat /sys/bus/iio/devices/iio:device0/scan_elements/in_accel_y_type + le:s12/16>>4 + +A user space application will interpret data samples read from the buffer as two +byte little endian signed data, that needs a 4 bits right shift before masking +out the 12 valid bits of data. diff --git a/Documentation/iio/index.rst b/Documentation/iio/index.rst index db341b45397f..206a0aff5ca1 100644 --- a/Documentation/iio/index.rst +++ b/Documentation/iio/index.rst @@ -8,6 +8,7 @@ Industrial I/O :maxdepth: 1 iio_configfs + iio_devbuf Industrial I/O Kernel Drivers =============================