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 <shua...@osg.samsung.com> --- 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 <shua...@osg.samsung.com> + * Copyright (c) 2016 Samsung Electronics Co., Ltd. + * + * This file is released under the GPLv2. + * Credits: Suggested by Laurent Pinchart <laurent.pinch...@ideasonboard.com> + */ + +/* + * 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 <linux/slab.h> +#include <linux/kref.h> +#include <linux/usb.h> +#include <media/media-device.h> + +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 <shua...@osg.samsung.com> + * Copyright (c) 2016 Samsung Electronics Co., Ltd. + * + * This file is released under the GPLv2. + * Credits: Suggested by Laurent Pinchart <laurent.pinch...@ideasonboard.com> + */ + +/* + * 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 -- 2.7.4