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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=ham 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 4BD63C433E0 for ; Sun, 24 May 2020 16:40:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 277C320826 for ; Sun, 24 May 2020 16:40:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590338445; bh=vccSXEaHfRL+UwNBweWaA0wqxU43n1ZHmahZIMV99LM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=EGX0UWdTtbQkv7P5jye7Qk5LBG2wdEPQHZU2VJv7IMlWJ+aWEBe1GhXE/RqjdeKLH Svus40NkmcOLid8J4N//xKcaFjjwby9i8JD21LMKEWONI/Gv0jmckEBgqj0WqXaSYq ZB05ryqakNPirbmtx1Bx2NE5uI1mBOD2/mX8DZ7c= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728684AbgEXQko (ORCPT ); Sun, 24 May 2020 12:40:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:60190 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727899AbgEXQko (ORCPT ); Sun, 24 May 2020 12:40:44 -0400 Received: from archlinux (cpc149474-cmbg20-2-0-cust94.5-4.cable.virginm.net [82.4.196.95]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 030DF20787; Sun, 24 May 2020 16:40:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590338443; bh=vccSXEaHfRL+UwNBweWaA0wqxU43n1ZHmahZIMV99LM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=wf9ywyog6rPq0mLcfqzIvtv67NWYl+HSsM228j2gzjgEItASiBt54ma/mfbdmImk+ TInTpoGzhZVcFoXUhwTbV6YDWo+n9/gVTOG2usBg/Y6jsgZJsMAq7pKqfW3npQNlAp YtiRk3ARpfVeidlaGY+nXqbQfjzaN/RPLus9yeZk= Date: Sun, 24 May 2020 17:40:39 +0100 From: Jonathan Cameron To: Alexandru Ardelean Cc: , , Subject: Re: [RFC PATCH 05/14] iio: core: register chardev only if needed Message-ID: <20200524174039.45867247@archlinux> In-Reply-To: <20200508135348.15229-6-alexandru.ardelean@analog.com> References: <20200508135348.15229-1-alexandru.ardelean@analog.com> <20200508135348.15229-6-alexandru.ardelean@analog.com> X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Fri, 8 May 2020 16:53:39 +0300 Alexandru Ardelean wrote: > The final intent is to localize all buffer ops into the > industrialio-buffer.c file, to be able to add support for multiple buffers > per IIO device. > > We only need a chardev if we need to support buffers and/or events. > > With this change, a chardev will be created only if an IIO buffer is > attached OR an event_interface is configured. > > Otherwise, no chardev will be created, and the IIO device will get > registered with the 'device_add()' call. > > Quite a lot of IIO devices don't really need a chardev, so this is a minor > improvement to the IIO core, as the IIO device will take up (slightly) > fewer resources. > > What's important to remember, is that removing a chardev also requires that > 'indio_dev->dev.devt' to be initialized. If it is, a '/dev/iio:deviceX' > file will be created by the kernel, regardless of whether it has a chardev > attached to it or not. > If that field is not initialized, cdev_device_{add,del}() behave{s} like > device_{add,del}(). > > Also, since we plan to add more chardevs for IIO buffers, we need to > consider now a separate IDA object just for chardevs. > Currently, the only benefit is that chardev IDs will be continuous. > However, when adding a chardev per IIO buffer, the IDs for the chardev > could outpace the IDs for IIO devices, so these should be decoupled. Given we are still discussing the need for more chardevs I guess we can't look at patches after this one 'yet'. Up until here they were all fine independent of the rest of the series. I was wondering if I could pick up the first part as it is useful whatever path we take with the rest of the series! Jonathan > > Signed-off-by: Alexandru Ardelean > --- > drivers/iio/industrialio-core.c | 58 +++++++++++++++++++++++++++++---- > 1 file changed, 51 insertions(+), 7 deletions(-) > > diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c > index 32c489139cd2..d74279efeca4 100644 > --- a/drivers/iio/industrialio-core.c > +++ b/drivers/iio/industrialio-core.c > @@ -35,6 +35,9 @@ > /* IDA to assign each registered device a unique id */ > static DEFINE_IDA(iio_ida); > > +/* IDA to assign each registered character device a unique id */ > +static DEFINE_IDA(iio_chrdev_ida); > + > static dev_t iio_devt; > > #define IIO_DEV_MAX 256 > @@ -1680,8 +1683,40 @@ static int iio_check_unique_scan_index(struct iio_dev *indio_dev) > return 0; > } > > +static int iio_device_alloc_chrdev_id(struct device *dev) > +{ > + int id; > + > + id = ida_simple_get(&iio_chrdev_ida, 0, 0, GFP_KERNEL); > + if (id < 0) { > + /* cannot use a dev_err as the name isn't available */ > + dev_err(dev, "failed to get device id\n"); > + return id; > + } > + > + dev->devt = MKDEV(MAJOR(iio_devt), id); > + > + return 0; > +} > + > +static void iio_device_free_chrdev_id(struct device *dev) > +{ > + if (!dev->devt) > + return; > + ida_simple_remove(&iio_chrdev_ida, MINOR(dev->devt)); > +} > + > static const struct iio_buffer_setup_ops noop_ring_setup_ops; > > +static const struct file_operations iio_event_fileops = { > + .owner = THIS_MODULE, > + .llseek = noop_llseek, > + .unlocked_ioctl = iio_ioctl, > + .compat_ioctl = compat_ptr_ioctl, > + .open = iio_chrdev_open, > + .release = iio_chrdev_release, > +}; > + > int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod) > { > int ret; > @@ -1701,9 +1736,6 @@ int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod) > if (ret < 0) > return ret; > > - /* configure elements for the chrdev */ > - indio_dev->dev.devt = MKDEV(MAJOR(iio_devt), indio_dev->id); > - > iio_device_register_debugfs(indio_dev); > > ret = iio_buffer_alloc_sysfs_and_mask(indio_dev); > @@ -1732,16 +1764,27 @@ int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod) > indio_dev->setup_ops == NULL) > indio_dev->setup_ops = &noop_ring_setup_ops; > > - cdev_init(&indio_dev->chrdev, &iio_buffer_fileops); > + if (indio_dev->buffer) > + cdev_init(&indio_dev->chrdev, &iio_buffer_fileops); > + else if (indio_dev->event_interface) > + cdev_init(&indio_dev->chrdev, &iio_event_fileops); > > - indio_dev->chrdev.owner = this_mod; > + if (indio_dev->buffer || indio_dev->event_interface) { > + indio_dev->chrdev.owner = this_mod; > + > + ret = iio_device_alloc_chrdev_id(&indio_dev->dev); > + if (ret) > + goto error_unreg_eventset; > + } > > ret = cdev_device_add(&indio_dev->chrdev, &indio_dev->dev); > - if (ret < 0) > - goto error_unreg_eventset; > + if (ret) > + goto error_free_chrdev_id; > > return 0; > > +error_free_chrdev_id: > + iio_device_free_chrdev_id(&indio_dev->dev); > error_unreg_eventset: > iio_device_unregister_eventset(indio_dev); > error_free_sysfs: > @@ -1761,6 +1804,7 @@ EXPORT_SYMBOL(__iio_device_register); > void iio_device_unregister(struct iio_dev *indio_dev) > { > cdev_device_del(&indio_dev->chrdev, &indio_dev->dev); > + iio_device_free_chrdev_id(&indio_dev->dev); > > mutex_lock(&indio_dev->info_exist_lock); >