From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from lb1-smtp-cloud3.xs4all.net ([194.109.24.22]:42233 "EHLO lb1-smtp-cloud3.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755234AbcE0VVm (ORCPT ); Fri, 27 May 2016 17:21:42 -0400 Subject: Re: [PATCH v3] media: Media Device Allocator API To: Shuah Khan , mchehab@osg.samsung.com, laurent.pinchart@ideasonboard.com, sakari.ailus@iki.fi, hans.verkuil@cisco.com, chehabrafael@gmail.com, javier@osg.samsung.com, inki.dae@samsung.com, g.liakhovetski@gmx.de, jh1009.sung@samsung.com References: <1464380735-4527-1-git-send-email-shuahkh@osg.samsung.com> Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org From: Hans Verkuil Message-ID: <5748BA5F.3090001@xs4all.nl> Date: Fri, 27 May 2016 23:21:35 +0200 MIME-Version: 1.0 In-Reply-To: <1464380735-4527-1-git-send-email-shuahkh@osg.samsung.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 05/27/2016 10:25 PM, 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 Regards, Hans > --- > > Changes since v2: > -- Addressed Hans's comments on v2 > > drivers/media/Makefile | 3 +- > drivers/media/media-dev-allocator.c | 114 ++++++++++++++++++++++++++++++++++++ > include/media/media-dev-allocator.h | 85 +++++++++++++++++++++++++++ > 3 files changed, 201 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 e608bbc..b08f091 100644 > --- a/drivers/media/Makefile > +++ b/drivers/media/Makefile > @@ -2,7 +2,8 @@ > # 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 > > # > # 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..21d5337 > --- /dev/null > +++ b/drivers/media/media-dev-allocator.c > @@ -0,0 +1,114 @@ > +/* > + * 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 > + > +static LIST_HEAD(media_device_list); > +static DEFINE_MUTEX(media_device_lock); > + > +struct media_device_instance { > + struct media_device mdev; > + 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) > +{ > + struct media_device_instance *mdi; > + > + list_for_each_entry(mdi, &media_device_list, list) { > + if (mdi->dev == dev) { > + kref_get(&mdi->refcount); > + dev_dbg(dev, "%s: get mdev=%p\n", > + __func__, &mdi->mdev); > + return &mdi->mdev; > + } > + } > + > + mdi = kzalloc(sizeof(*mdi), GFP_KERNEL); > + if (!mdi) > + return NULL; > + > + mdi->dev = dev; > + kref_init(&mdi->refcount); > + list_add_tail(&mdi->list, &media_device_list); > + > + dev_dbg(dev, "%s: alloc mdev=%p\n", __func__, &mdi->mdev); > + return &mdi->mdev; > +} > + > +struct media_device *media_device_usb_allocate(struct usb_device *udev, > + char *driver_name) > +{ > + struct media_device *mdev; > + > + mutex_lock(&media_device_lock); > + mdev = __media_device_get(&udev->dev); > + 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, > + driver_name); > + mutex_unlock(&media_device_lock); > + > + dev_dbg(&udev->dev, "%s\n", __func__); > + return mdev; > +} > +EXPORT_SYMBOL_GPL(media_device_usb_allocate); > + > +void media_device_delete(struct media_device *mdev) > +{ > + struct media_device_instance *mdi = to_media_device_instance(mdev); > + > + dev_dbg(mdi->mdev.dev, "%s: mdev=%p\n", __func__, &mdi->mdev); > + 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..fda032b > --- /dev/null > +++ b/include/media/media-dev-allocator.h > @@ -0,0 +1,85 @@ > +/* > + * 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 > + * @driver_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 *driver_name); > +/** > + * media_device_delete() - Release media device. Calls kref_put(). > + * > + * @mdev - struct media_device pointer > + * > + * This interface should be called to put Media Device Instance kref. > + */ > +void media_device_delete(struct media_device *mdev); > +#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) { } > +#endif /* CONFIG_MEDIA_CONTROLLER */ > +#endif >