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=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 45FD1C55199 for ; Sun, 26 Apr 2020 10:22:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1F4052075B for ; Sun, 26 Apr 2020 10:22:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587896527; bh=sewOCwfu0X7Pc73k2jUc1GT5PUZNvaMiQZoku5O5PRg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=x+W+Mj3LMAr8SHkrsgA+5mZ5zfqc1kiWtfENhClXQP17FVjYrWCMVVKE/onJJ4TzL uCAuwifck64Z7wBxFADYuxVWymCYOOSBpVVmL1y59ZT6ICeCgHAL3mOnv6LnuHBJ9Y g3NW/IU9LJYH/iHwl88d45OwhLM1HYbltm2s0S38= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726143AbgDZKWF (ORCPT ); Sun, 26 Apr 2020 06:22:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:55906 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726116AbgDZKWC (ORCPT ); Sun, 26 Apr 2020 06:22:02 -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 D6FFA20700; Sun, 26 Apr 2020 10:22:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587896521; bh=sewOCwfu0X7Pc73k2jUc1GT5PUZNvaMiQZoku5O5PRg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=tSvpbGZHpLMXg0sbjlG0qiVYQ4WEQgaUuXc6ktpsefBViJXLdgKeUsfiQRCDruD2L g1fVjuiEYUCYL0XR9OQSFbEfUCkbKqa7aWYpzQUCAGqqo2EEluEZe/Fb6KWi/FHW5S gLy54dwOd3WR3jEo2TWPHuYOPOKOS0QDdgJ8rw3o= Date: Sun, 26 Apr 2020 11:21:57 +0100 From: Jonathan Cameron To: Alexandru Ardelean Cc: , , , Subject: Re: [PATCH v5 5/6] iio: core: add simple centralized mechanism for ioctl() handlers Message-ID: <20200426112157.51b16616@archlinux> In-Reply-To: <20200426111037.076b984d@archlinux> References: <20200426073817.33307-1-alexandru.ardelean@analog.com> <20200426073817.33307-6-alexandru.ardelean@analog.com> <20200426111037.076b984d@archlinux> 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-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 26 Apr 2020 11:10:37 +0100 Jonathan Cameron wrote: > On Sun, 26 Apr 2020 10:38:16 +0300 > Alexandru Ardelean wrote: > > > The aim of this is to reduce the organization violation of ioctl() calls in > > IIO core. Currently, since the chardev is split across files, event ioctl() > > calls need to be called in buffer ioctl() calls. > > > > The 'industrialio-core.c' file will provide a 'iio_device_ioctl()' which > > will iterate over a list of ioctls registered with the IIO device. These > > can be event ioctl() or buffer ioctl() calls, or something else. > > This is needed, since there is currently one chardev per IIO device and > > that is used for both event handling and reading from the buffer. > > > > Each ioctl() will have to return a IIO_IOCTL_UNHANDLED code (which is > > positive 1), if the ioctl() did not handle the call in any. This eliminates > > any potential ambiguities; if we were to have used error codes it would > > have been uncertain whether they were actual errors, or whether > > the registered ioctl() doesn't service the command. > > > > If any ioctl() returns 0, it was considered that it was serviced > > successfully and the loop will exit. > > > > One assumption for all registered ioctl() handlers is that they are > > statically allocated, so the iio_device_unregister() which just remove all > > of them from the device's ioctl() handler list. > > > > Also, something that is a bit hard to do [at this point] and may not be > > worth the effort of doing, is to check whether registered ioctl() > > calls/commands overlap. This should be unlikely to happen, and should get > > caught at review time. Though, new ioctl() calls would likely not be added > > too often. > > > > Signed-off-by: Alexandru Ardelean > > A question on locking inline. Otherwise this looks fairly clean and simple > to me. > > Jonathan > > > > --- > > drivers/iio/iio_core.h | 14 ++++++++++++++ > > drivers/iio/industrialio-core.c | 33 +++++++++++++++++++++++++++++++++ > > include/linux/iio/iio.h | 2 ++ > > 3 files changed, 49 insertions(+) > > > > diff --git a/drivers/iio/iio_core.h b/drivers/iio/iio_core.h > > index a527a66be9e5..34c3e19229d8 100644 > > --- a/drivers/iio/iio_core.h > > +++ b/drivers/iio/iio_core.h > > @@ -17,6 +17,20 @@ struct iio_dev; > > > > extern struct device_type iio_device_type; > > > > +#define IIO_IOCTL_UNHANDLED 1 > > +struct iio_ioctl_handler { > > + struct list_head entry; > > + long (*ioctl)(struct iio_dev *indio_dev, struct file *filp, > > + unsigned int cmd, unsigned long arg); > > +}; > > + > > +long iio_device_ioctl(struct iio_dev *indio_dev, struct file *filp, > > + unsigned int cmd, unsigned long arg); > > + > > +void iio_device_ioctl_handler_register(struct iio_dev *indio_dev, > > + struct iio_ioctl_handler *h); > > +void iio_device_ioctl_handler_unregister(struct iio_ioctl_handler *h); > > + > > int __iio_add_chan_devattr(const char *postfix, > > struct iio_chan_spec const *chan, > > ssize_t (*func)(struct device *dev, > > diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c > > index aec585cc8453..79e8fa8ff70b 100644 > > --- a/drivers/iio/industrialio-core.c > > +++ b/drivers/iio/industrialio-core.c > > @@ -1531,6 +1531,7 @@ struct iio_dev *iio_device_alloc(int sizeof_priv) > > } > > dev_set_name(&dev->dev, "iio:device%d", dev->id); > > INIT_LIST_HEAD(&dev->buffer_list); > > + INIT_LIST_HEAD(&dev->ioctl_handlers); > > > > return dev; > > } > > @@ -1584,6 +1585,33 @@ struct iio_dev *devm_iio_device_alloc(struct device *dev, int sizeof_priv) > > } > > EXPORT_SYMBOL_GPL(devm_iio_device_alloc); > > > > +void iio_device_ioctl_handler_register(struct iio_dev *indio_dev, > > + struct iio_ioctl_handler *h) > > +{ > > + /* this assumes that all ioctl() handlers are statically allocated */ > > + list_add_tail(&h->entry, &indio_dev->ioctl_handlers); > > +} > > + > > +long iio_device_ioctl(struct iio_dev *indio_dev, struct file *filp, > > + unsigned int cmd, unsigned long arg) > > +{ > > + struct iio_ioctl_handler *h; > > + int ret; > > + > > + if (!indio_dev->info) > > + return -ENODEV; > > + > > + list_for_each_entry(h, &indio_dev->ioctl_handlers, entry) { > > + ret = h->ioctl(indio_dev, filp, cmd, arg); > > + if (ret == 0) > > + return 0; > > + if (ret != IIO_IOCTL_UNHANDLED) > > + return ret; > > + } > > + > > + return -EINVAL; > > +} > > + > > static int iio_check_unique_scan_index(struct iio_dev *indio_dev) > > { > > int i, j; > > @@ -1695,6 +1723,8 @@ EXPORT_SYMBOL(__iio_device_register); > > **/ > > void iio_device_unregister(struct iio_dev *indio_dev) > > { > > + struct iio_ioctl_handler *h, *t; > > + > > if (indio_dev->chrdev) > > cdev_device_del(indio_dev->chrdev, &indio_dev->dev); > > else > > @@ -1708,6 +1738,9 @@ void iio_device_unregister(struct iio_dev *indio_dev) > > > > iio_disable_all_buffers(indio_dev); > > > > + list_for_each_entry_safe(h, t, &indio_dev->ioctl_handlers, entry) > > + list_del(&h->entry); > > + > > Is there any chance anything is walking that list whilst we are deleting it? > I think this needs to happen under a lock as does the walk. We may want to use the rcu methods to make the walk and delete safe whilst avoiding heavy weight locking on the read path linux/rculist.h I've not thought about this in much depth though so take that advice as a vague suggestion and nothing more! > > > indio_dev->info = NULL; > > > > iio_device_wakeup_eventset(indio_dev); > > diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h > > index 52992be44e9e..b6ca8d85629e 100644 > > --- a/include/linux/iio/iio.h > > +++ b/include/linux/iio/iio.h > > @@ -488,6 +488,7 @@ struct iio_buffer_setup_ops { > > * @currentmode: [DRIVER] current operating mode > > * @dev: [DRIVER] device structure, should be assigned a parent > > * and owner > > + * @ioctl_handlers: [INTERN] list of registered ioctl handlers > > * @event_interface: [INTERN] event chrdevs associated with interrupt lines > > * @buffer: [DRIVER] any buffer present > > * @buffer_list: [INTERN] list of all buffers currently attached > > @@ -529,6 +530,7 @@ struct iio_dev { > > int modes; > > int currentmode; > > struct device dev; > > + struct list_head ioctl_handlers; > > > > struct iio_event_interface *event_interface; > > >