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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1963BC83F01 for ; Thu, 31 Aug 2023 16:14:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345117AbjHaQOc (ORCPT ); Thu, 31 Aug 2023 12:14:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46762 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236397AbjHaQOb (ORCPT ); Thu, 31 Aug 2023 12:14:31 -0400 Received: from mx08-00178001.pphosted.com (mx08-00178001.pphosted.com [91.207.212.93]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E34A31B0; Thu, 31 Aug 2023 09:14:28 -0700 (PDT) Received: from pps.filterd (m0369457.ppops.net [127.0.0.1]) by mx07-00178001.pphosted.com (8.17.1.22/8.17.1.22) with ESMTP id 37VE3TsM012289; Thu, 31 Aug 2023 18:14:13 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=foss.st.com; h= message-id:date:mime-version:from:subject:to:cc:references :in-reply-to:content-type:content-transfer-encoding; s= selector1; bh=1YiWnfqTSJwEqmD8zgssWIDW581bRoV7B7MWFLNnKqk=; b=Ze LuWjziX0p8wxdvAOxHTH1TKurdSN/SFQwbDD8U72oN8rpJHxKLqe/J/jS4ZYOySl wvbqESalb870/mEmikcqVxoei4B1hv1cO7bqg6QUP+6ex0EMMqHG48uYYiR2fZUx X77J82Hsw4yrxCLtux5hzkgJgH/WQjQn1FebttdNNgXPJcYYWsPhPlsGg4Bf0vB6 QVk1J/yLbMNp3vwPPZU65CH7cL8s+XHaGNo/bvCvoxIfVIesiNF8aM9CjdmEJ9Bg o04cm4+x1MzUNmrsbZDHxodfZrPTxfRbTQIa4SCb0Fh0v/aiPXOTUHvzH9grao4+ +YkVoeRltRGy73DRnajw== Received: from beta.dmz-eu.st.com (beta.dmz-eu.st.com [164.129.1.35]) by mx07-00178001.pphosted.com (PPS) with ESMTPS id 3sqvbhmb7w-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 31 Aug 2023 18:14:13 +0200 (MEST) Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id 35CED100056; Thu, 31 Aug 2023 18:14:13 +0200 (CEST) Received: from Webmail-eu.st.com (shfdag1node1.st.com [10.75.129.69]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 2D1A921ADC5; Thu, 31 Aug 2023 18:14:13 +0200 (CEST) Received: from [10.201.20.178] (10.201.20.178) by SHFDAG1NODE1.st.com (10.75.129.69) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.21; Thu, 31 Aug 2023 18:14:12 +0200 Message-ID: <095f9c64-bcac-e838-ba69-b5df623c444f@foss.st.com> Date: Thu, 31 Aug 2023 18:14:12 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 From: Olivier MOYSAN Subject: Re: [RFC v2 01/11] iio: introduce iio backend device To: =?UTF-8?Q?Nuno_S=c3=a1?= , Jonathan Cameron , Lars-Peter Clausen CC: , , "Fabrice GASNIER" References: <20230727150324.1157933-1-olivier.moysan@foss.st.com> <20230727150324.1157933-2-olivier.moysan@foss.st.com> <7ec3fe6183409c218b97a3359e951731b47fe16d.camel@gmail.com> Content-Language: en-US In-Reply-To: <7ec3fe6183409c218b97a3359e951731b47fe16d.camel@gmail.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.201.20.178] X-ClientProxiedBy: EQNCAS1NODE3.st.com (10.75.129.80) To SHFDAG1NODE1.st.com (10.75.129.69) X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.957,Hydra:6.0.601,FMLib:17.11.176.26 definitions=2023-08-31_14,2023-08-31_01,2023-05-22_02 Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org Hi Nuno, On 7/28/23 10:42, Nuno Sá wrote: > Hi Olivier, > > On Thu, 2023-07-27 at 17:03 +0200, Olivier Moysan wrote: >> Add a new device type in IIO framework. >> This backend device does not compute channel attributes and does not expose >> them through sysfs, as done typically in iio-rescale frontend device. >> Instead, it allows to report information applying to channel >> attributes through callbacks. These backend devices can be cascaded >> to represent chained components. >> An IIO device configured as a consumer of a backend device can compute >> the channel attributes of the whole chain. >> >> Signed-off-by: Olivier Moysan >> --- >>  drivers/iio/Makefile               |   1 + >>  drivers/iio/industrialio-backend.c | 107 +++++++++++++++++++++++++++++ >>  include/linux/iio/backend.h        |  56 +++++++++++++++ >>  3 files changed, 164 insertions(+) >>  create mode 100644 drivers/iio/industrialio-backend.c >>  create mode 100644 include/linux/iio/backend.h >> >> diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile >> index 9622347a1c1b..9b59c6ab1738 100644 >> --- a/drivers/iio/Makefile >> +++ b/drivers/iio/Makefile >> @@ -5,6 +5,7 @@ >> >>  obj-$(CONFIG_IIO) += industrialio.o >>  industrialio-y := industrialio-core.o industrialio-event.o inkern.o >> +industrialio-$(CONFIG_IIO_BACKEND) += industrialio-backend.o >>  industrialio-$(CONFIG_IIO_BUFFER) += industrialio-buffer.o >>  industrialio-$(CONFIG_IIO_TRIGGER) += industrialio-trigger.o >> >> diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio- >> backend.c >> new file mode 100644 >> index 000000000000..7d0625889873 >> --- /dev/null >> +++ b/drivers/iio/industrialio-backend.c >> @@ -0,0 +1,107 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +/* The industrial I/O core, backend handling functions >> + * >> + */ >> + >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +static DEFINE_IDA(iio_backend_ida); >> + >> +#define to_iio_backend(_device) container_of((_device), struct iio_backend, >> dev) >> + >> +static void iio_backend_release(struct device *device) >> +{ >> +       struct iio_backend *backend = to_iio_backend(device); >> + >> +       kfree(backend->name); >> +       kfree(backend); >> +} >> + >> +static const struct device_type iio_backend_type = { >> +       .release = iio_backend_release, >> +       .name = "iio_backend_device", >> +}; >> + >> +struct iio_backend *iio_backend_alloc(struct device *parent) >> +{ >> +       struct iio_backend *backend; >> + >> +       backend = devm_kzalloc(parent, sizeof(*backend), GFP_KERNEL); >> > > No error checking. > > I guess a lot of cleanings are still missing but the important thing I wanted to > notice is that the above pattern is not ok. > Your 'struct iio_backend *backend'' embeds a 'stuct device' which is a > refcounted object. Nevertheless, you're binding the lifetime of your object to > the parent device and that is wrong. The reason is that as soon as your parent > device get's released or just unbinded from it's driver, all the devres stuff > (including your 'struct iio_backend' object) will be released independentof > your 'struct device' refcount value... > > So, you might argue this won't ever be an issue in here but the pattern is still > wrong. There are some talks about this, the last one was given at the latest > EOSS: > > https://www.youtube.com/watch?v=HCiJL7djGw8&list=PLbzoR-pLrL6pY8a8zSKRC6-AihFrruOkq&index=27&ab_channel=TheLinuxFoundation > This is a good point. Thanks for pointing it out. Sure, there are still many things to improve. I have seen the comment from Jonathan on your "Add converter framework" serie. I had a quick look at the serie. It seems that we share the need to aggregate some IIO devices. But I need to read it more carefully to check if we can find some convergences here. BRs Olivier > - Nuno Sá > >