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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 B7F44C43441 for ; Tue, 20 Nov 2018 11:21:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ABA2020831 for ; Tue, 20 Nov 2018 11:20:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ABA2020831 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xs4all.nl Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728041AbeKTVtR (ORCPT ); Tue, 20 Nov 2018 16:49:17 -0500 Received: from lb1-smtp-cloud8.xs4all.net ([194.109.24.21]:54600 "EHLO lb1-smtp-cloud8.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726708AbeKTVtQ (ORCPT ); Tue, 20 Nov 2018 16:49:16 -0500 Received: from [IPv6:2001:983:e9a7:1:1da9:d909:50bf:c42e] ([IPv6:2001:983:e9a7:1:1da9:d909:50bf:c42e]) by smtp-cloud8.xs4all.net with ESMTPA id P452ghEsqcvkSP453ggzzc; Tue, 20 Nov 2018 12:20:35 +0100 Subject: Re: [RFC PATCH v8 1/4] media: Media Device Allocator API To: shuah@kernel.org, mchehab@kernel.org, perex@perex.cz, tiwai@suse.com Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org References: From: Hans Verkuil Message-ID: <0412cf12-8f2f-4a63-74da-6f92dd503c4b@xs4all.nl> Date: Tue, 20 Nov 2018 12:20:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-CMAE-Envelope: MS4wfIR6f2zSGBD8F2BEck7lGx+TIjDRd/vdY/Kjcy9DOUUu0chLgrEN4mwCSnOiC+/9U9862GbZwlzZmKWHcuMJ/im/7jQGDO6GtXRtjmtGiEg9LRcscZx5 ukrV2orPUeaEnKgfQIqNWgoZo14+dbNqrhlK9ew1WqYxOd1VvEN9STqgRrHGopeIsudKqC6M2TjgmqhElD5aCXhUYmmc01bDO+75EmFEG7up14QuAlXVVsCI qqgAG2X4a5mgPTpwkSAmVw6EdXHVNYzd+jBa7IgLLqrUQ2f9bEVz84pvGGkD00e0IImxKRrdj4CKguaUnGxmRpPcd61wyOwYaT3vPT39m5lE4bX1Fns0Yb2I 5yY5TnKGwaguysTYQROOaG81EjGaSMkBQADx/FAKFGl0+ScNeB5SKSzqJMN5L/wDd1RGAbuQI/+y1Ji1ZGI7ceWcJEr2HSnxDyWS1Ue3WrPdbSf6uw0= Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/02/2018 01:31 AM, shuah@kernel.org wrote: > From: Shuah Khan > > Media Device Allocator API to allows multiple drivers share a media device. > Using this API, drivers can allocate a media device with the shared struct > device as the key. Once the media device is allocated by a driver, other > drivers can get a reference to it. The media device is released when all > the references are released. > > Signed-off-by: Shuah Khan > --- > Documentation/media/kapi/mc-core.rst | 37 ++++++++ > drivers/media/Makefile | 3 +- > drivers/media/media-dev-allocator.c | 132 +++++++++++++++++++++++++++ > include/media/media-dev-allocator.h | 53 +++++++++++ > 4 files changed, 224 insertions(+), 1 deletion(-) > create mode 100644 drivers/media/media-dev-allocator.c > create mode 100644 include/media/media-dev-allocator.h > > diff --git a/Documentation/media/kapi/mc-core.rst b/Documentation/media/kapi/mc-core.rst > index 0c05503eaf1f..d6f409598065 100644 > --- a/Documentation/media/kapi/mc-core.rst > +++ b/Documentation/media/kapi/mc-core.rst > @@ -257,8 +257,45 @@ Subsystems should facilitate link validation by providing subsystem specific > helper functions to provide easy access for commonly needed information, and > in the end provide a way to use driver-specific callbacks. > > +Media Controller Device Allocator API > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > +When media device belongs to more than one driver, the shared media device When -> When the > +is allocated with the shared struct device as the key for look ups. > + > +Shared media device should stay in registered state until the last driver Shared -> The shared > +unregisters it. In addition, media device should be released when all the media -> the media > +references are released. Each driver gets a reference to the media device > +during probe, when it allocates the media device. If media device is already > +allocated, allocate API bumps up the refcount and return the existing media allocate -> the allocate return -> returns > +device. Driver puts the reference back from its disconnect routine when it Driver -> The driver from -> in > +calls :c:func:`media_device_delete()`. > + > +Media device is unregistered and cleaned up from the kref put handler to Media -> The media from -> in > +ensure that the media device stays in registered state until the last driver > +unregisters the media device. What happens if an application still has the media device open and you forcibly remove the last driver? I think it should be OK since the media_devnode struct isn't freed until the last open filehandle closes. But it is good to test this. > + > +**Driver Usage** > + > +Drivers should use the media-core routines to get register reference and 'get register reference'? Not sure what you meant to say. > +call :c:func:`media_device_delete()` routine to make sure the shared media > +device delete is handled correctly. > + > +**driver probe:** > +Call :c:func:`media_device_usb_allocate()` to allocate or get a reference > +Call :c:func:`media_device_register()`, if media devnode isn't registered > + > +**driver disconnect:** > +Call :c:func:`media_device_delete()` to free the media_device. Free'ing is Free'ing -> Freeing > +handled by the kref put handler. > + > +API Definitions > +^^^^^^^^^^^^^^^ > + > .. kernel-doc:: include/media/media-device.h > > .. kernel-doc:: include/media/media-devnode.h > > .. kernel-doc:: include/media/media-entity.h > + > +.. kernel-doc:: include/media/media-dev-allocator.h > diff --git a/drivers/media/Makefile b/drivers/media/Makefile > index 594b462ddf0e..8608f0a41dca 100644 > --- a/drivers/media/Makefile > +++ b/drivers/media/Makefile > @@ -3,7 +3,8 @@ > # Makefile for the kernel multimedia device drivers. > # > > -media-objs := media-device.o media-devnode.o media-entity.o > +media-objs := media-device.o media-devnode.o media-entity.o \ > + media-dev-allocator.o Perhaps only add media-dev-allocator if CONFIG_USB is enabled? > > # > # I2C drivers should come before other drivers, otherwise they'll fail > diff --git a/drivers/media/media-dev-allocator.c b/drivers/media/media-dev-allocator.c > new file mode 100644 > index 000000000000..262d1293dc13 > --- /dev/null > +++ b/drivers/media/media-dev-allocator.c > @@ -0,0 +1,132 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * media-dev-allocator.c - Media Controller Device Allocator API > + * > + * Copyright (c) 2018 Shuah Khan > + * > + * Credits: Suggested by Laurent Pinchart > + */ > + > +/* > + * This file adds a global refcounted Media Controller Device Instance API. > + * A system wide global media device list is managed and each media device > + * includes a kref count. The last put on the media device releases the media > + * device instance. > + * > + */ > + > +#include > +#include > +#include > +#include > + > +#include > + > +static LIST_HEAD(media_device_list); > +static DEFINE_MUTEX(media_device_lock); > + > +struct media_device_instance { > + struct media_device mdev; > + struct module *owner; > + struct list_head list; > + struct kref refcount; > +}; > + > +static inline struct media_device_instance * > +to_media_device_instance(struct media_device *mdev) > +{ > + return container_of(mdev, struct media_device_instance, mdev); > +} > + > +static void media_device_instance_release(struct kref *kref) > +{ > + struct media_device_instance *mdi = > + container_of(kref, struct media_device_instance, refcount); > + > + dev_dbg(mdi->mdev.dev, "%s: mdev=%p\n", __func__, &mdi->mdev); > + > + mutex_lock(&media_device_lock); Can't the lock be moved down to just before list_del? Or am I missing something? > + > + media_device_unregister(&mdi->mdev); > + media_device_cleanup(&mdi->mdev); > + > + list_del(&mdi->list); > + mutex_unlock(&media_device_lock); > + > + kfree(mdi); > +} > + > +/* Callers should hold media_device_lock when calling this function */ > +static struct media_device *__media_device_get(struct device *dev, > + char *module_name) const char * > +{ > + struct media_device_instance *mdi; > + > + list_for_each_entry(mdi, &media_device_list, list) { > + if (mdi->mdev.dev != dev) > + continue; > + > + kref_get(&mdi->refcount); > + /* get module reference for the media_device owner */ > + if (find_module(module_name) != mdi->owner && > + !try_module_get(mdi->owner)) > + dev_err(dev, "%s: try_module_get() error\n", __func__); > + dev_dbg(dev, "%s: get mdev=%p module_name %s\n", > + __func__, &mdi->mdev, module_name); > + return &mdi->mdev; > + } > + > + mdi = kzalloc(sizeof(*mdi), GFP_KERNEL); > + if (!mdi) > + return NULL; > + > + mdi->owner = find_module(module_name); > + kref_init(&mdi->refcount); > + list_add_tail(&mdi->list, &media_device_list); > + > + dev_dbg(dev, "%s: alloc mdev=%p module_name %s\n", __func__, > + &mdi->mdev, module_name); > + return &mdi->mdev; > +} > + > +#if IS_ENABLED(CONFIG_USB) > +struct media_device *media_device_usb_allocate(struct usb_device *udev, > + char *module_name) const char * > +{ > + struct media_device *mdev; > + > + mutex_lock(&media_device_lock); > + mdev = __media_device_get(&udev->dev, module_name); > + if (!mdev) { > + mutex_unlock(&media_device_lock); > + return ERR_PTR(-ENOMEM); > + } > + > + /* check if media device is already initialized */ > + if (!mdev->dev) > + __media_device_usb_init(mdev, udev, udev->product, > + module_name); > + mutex_unlock(&media_device_lock); > + return mdev; > +} > +EXPORT_SYMBOL_GPL(media_device_usb_allocate); > +#endif > + > +void media_device_delete(struct media_device *mdev, char *module_name) > +{ > + struct media_device_instance *mdi = to_media_device_instance(mdev); > + > + dev_dbg(mdi->mdev.dev, "%s: mdev=%p module_name %s\n", > + __func__, &mdi->mdev, module_name); > + > + mutex_lock(&media_device_lock); > + /* put module reference if media_device owner is not THIS_MODULE */ > + if (mdi->owner != find_module(module_name)) { > + module_put(mdi->owner); > + dev_dbg(mdi->mdev.dev, > + "%s decremented owner module reference\n", __func__); > + } > + mutex_unlock(&media_device_lock); > + kref_put(&mdi->refcount, media_device_instance_release); > +} > +EXPORT_SYMBOL_GPL(media_device_delete); > diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h > new file mode 100644 > index 000000000000..8fbadff2cef8 > --- /dev/null > +++ b/include/media/media-dev-allocator.h > @@ -0,0 +1,53 @@ > +/* SPDX-License-Identifier: GPL-2.0+ */ > +/* > + * media-dev-allocator.h - Media Controller Device Allocator API > + * > + * Copyright (c) 2018 Shuah Khan > + * > + * Credits: Suggested by Laurent Pinchart > + */ > + > +/* > + * This file adds a global ref-counted Media Controller Device Instance API. > + * A system wide global media device list is managed and each media device > + * includes a kref count. The last put on the media device releases the media > + * device instance. > + */ > + > +#ifndef _MEDIA_DEV_ALLOCTOR_H > +#define _MEDIA_DEV_ALLOCTOR_H > + > +struct usb_device; > + > +#ifdef CONFIG_MEDIA_CONTROLLER Perhaps change this to: #if defined(CONFIG_MEDIA_CONTROLLER) && defined(CONFIG_USB) Since for now this only makes sense for USB devices. > +/** > + * media_device_usb_allocate() - Allocate and return struct &media device > + * > + * @udev: struct &usb_device pointer > + * @module_name: should be filled with %KBUILD_MODNAME > + * > + * This interface should be called to allocate a Media Device when multiple > + * drivers share usb_device and the media device. This interface allocates > + * &media_device structure and calls media_device_usb_init() to initialize > + * it. > + * > + */ > +struct media_device *media_device_usb_allocate(struct usb_device *udev, > + char *module_name); > +/** > + * media_device_delete() - Release media device. Calls kref_put(). > + * > + * @mdev: struct &media_device pointer > + * @module_name: should be filled with %KBUILD_MODNAME > + * > + * This interface should be called to put Media Device Instance kref. > + */ > +void media_device_delete(struct media_device *mdev, char *module_name); > +#else > +static inline struct media_device *media_device_usb_allocate( > + struct usb_device *udev, char *module_name) > + { return NULL; } > +static inline void media_device_delete( > + struct media_device *mdev, char *module_name) { } > +#endif /* CONFIG_MEDIA_CONTROLLER */ > +#endif > Regards, Hans