From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933661AbcKPOkE (ORCPT ); Wed, 16 Nov 2016 09:40:04 -0500 Received: from ec2-52-27-115-49.us-west-2.compute.amazonaws.com ([52.27.115.49]:44416 "EHLO osg.samsung.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932816AbcKPOkB (ORCPT ); Wed, 16 Nov 2016 09:40:01 -0500 Subject: Re: [PATCH v4 1/3] media: Media Device Allocator API To: mchehab@kernel.org, perex@perex.cz, tiwai@suse.com, hans.verkuil@cisco.com, javier@osg.samsung.com, chehabrafael@gmail.com, g.liakhovetski@gmx.de, ONeukum@suse.com, k@oikw.org, daniel@zonque.org, mahasler@gmail.com, clemens@ladisch.de, geliangtang@163.com, vdronov@redhat.com, laurent.pinchart@ideasonboard.com References: <448169cd2db0ba7c8a455bd672e6709e6bada2aa.1479271294.git.shuahkh@osg.samsung.com> Cc: linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, alsa-devel@alsa-project.org, Shuah Khan From: Shuah Khan Message-ID: Date: Wed, 16 Nov 2016 07:39:57 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <448169cd2db0ba7c8a455bd672e6709e6bada2aa.1479271294.git.shuahkh@osg.samsung.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sorry for the duplicates. Replying to catch bounced emails on the original patch emails from git send-email On 11/16/2016 07:29 AM, Shuah Khan wrote: > 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 > Reviewed-by: Hans Verkuil > --- > Changes since v3: > - Fixed undefined reference to `__media_device_usb_init compile error when > CONFIG_USB is disabled. > - Fixed kernel paging error when accessing /dev/mediaX after rmmod of the > module that owns the media_device. The fix bumps the reference count for > the owner when second driver comes along to share the media_device. If > au0828 owns the media_device, then snd_usb_audio will bump the refcount > for au0828, so it won't get deleted and vice versa. > > drivers/media/Makefile | 3 +- > drivers/media/media-dev-allocator.c | 146 ++++++++++++++++++++++++++++++++++++ > include/media/media-dev-allocator.h | 87 +++++++++++++++++++++ > 3 files changed, 235 insertions(+), 1 deletion(-) > create mode 100644 drivers/media/media-dev-allocator.c > create mode 100644 include/media/media-dev-allocator.h > > diff --git a/drivers/media/Makefile b/drivers/media/Makefile > index 0deaa93..7c0701d 100644 > --- a/drivers/media/Makefile > +++ b/drivers/media/Makefile > @@ -6,7 +6,8 @@ ifeq ($(CONFIG_MEDIA_CEC_EDID),y) > obj-$(CONFIG_MEDIA_SUPPORT) += cec-edid.o > endif > > -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 > > # > # 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 0000000..014a317 > --- /dev/null > +++ b/drivers/media/media-dev-allocator.c > @@ -0,0 +1,146 @@ > +/* > + * media-dev-allocator.c - Media Controller Device Allocator API > + * > + * Copyright (c) 2016 Shuah Khan > + * Copyright (c) 2016 Samsung Electronics Co., Ltd. > + * > + * This file is released under the GPLv2. > + * 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 device *dev; > + 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); > + > + 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) > +{ > + struct media_device_instance *mdi; > + > + list_for_each_entry(mdi, &media_device_list, list) { > + if (mdi->dev == dev) { > + 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->dev = dev; > + 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) > +{ > + struct media_device *mdev; > + > + if (!module_name) { > + dev_err(&udev->dev, "%s Module Name is null\n", __func__); > + return ERR_PTR(-EINVAL); > + } > + > + 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); > + > + dev_dbg(&udev->dev, "%s\n", __func__); > + 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); > + > + if (!module_name) { > + dev_err(mdi->mdev.dev, "%s Module Name is null\n", __func__); > + return; > + } > + > + 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 0000000..45c437d > --- /dev/null > +++ b/include/media/media-dev-allocator.h > @@ -0,0 +1,87 @@ > +/* > + * media-dev-allocator.h - Media Controller Device Allocator API > + * > + * Copyright (c) 2016 Shuah Khan > + * Copyright (c) 2016 Samsung Electronics Co., Ltd. > + * > + * This file is released under the GPLv2. > + * 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 > +/** > + * DOC: Media Controller Device Allocator API > + * > + * When media device belongs to more than one driver, the shared media device > + * 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 > + * unregisters it. In addition, media device should be released when all the > + * 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 > + * device. Driver puts the reference back from its disconnect routine when it > + * calls media_device_delete(). > + * > + * Media device is unregistered and cleaned up from the kref put handler to > + * ensure that the media device stays in registered state until the last driver > + * unregisters the media device. > + * > + * Driver Usage: > + * > + * Drivers should use the media-core routines to get register reference and > + * call media_device_delete() routine to make sure the shared media device > + * delete is handled correctly. > + * > + * driver probe: > + * Call media_device_usb_allocate() to allocate or get a reference > + * Call media_device_register(), if media devnode isn't registered > + * > + * driver disconnect: > + * Call media_device_delete() to free the media_device. Free'ing is > + * handled by the put handler. > + * > + */ > + > +/** > + * media_device_usb_allocate() - Allocate and return media device > + * > + * @udev - struct usb_device pointer > + * @module_name > + * > + * 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 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 > + * > + * This interface should be called to put Media Device Instance kref. > + */ > +void media_device_delete(struct media_device *mdev, char *driver_name); > +#else > +static inline struct media_device *media_device_usb_allocate( > + struct usb_device *udev, char *driver_name) > + { return NULL; } > +static inline void media_device_delete( > + struct media_device *mdev, char *module_name) { } > +#endif /* CONFIG_MEDIA_CONTROLLER */ > +#endif >