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6e1d824e7a
Media Device Allocator API to allows multiple drivers share a media device. This API solves a very common use-case for media devices where one physical device (an USB stick) provides both audio and video. When such media device exposes a standard USB Audio class, a proprietary Video class, two or more independent drivers will share a single physical USB bridge. In such cases, it is necessary to coordinate access to the shared resource. 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 <shuah@kernel.org> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
64 lines
2.2 KiB
C
64 lines
2.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* media-dev-allocator.h - Media Controller Device Allocator API
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*
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* Copyright (c) 2019 Shuah Khan <shuah@kernel.org>
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*
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* Credits: Suggested by Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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*/
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/*
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* This file adds a global ref-counted Media Controller Device Instance API.
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* A system wide global media device list is managed and each media device
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* includes a kref count. The last put on the media device releases the media
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* device instance.
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*/
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#ifndef _MEDIA_DEV_ALLOCATOR_H
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#define _MEDIA_DEV_ALLOCATOR_H
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struct usb_device;
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#if defined(CONFIG_MEDIA_CONTROLLER) && defined(CONFIG_USB)
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/**
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* media_device_usb_allocate() - Allocate and return struct &media device
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*
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* @udev: struct &usb_device pointer
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* @module_name: should be filled with %KBUILD_MODNAME
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* @owner: struct module pointer %THIS_MODULE for the driver.
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* %THIS_MODULE is null for a built-in driver.
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* It is safe even when %THIS_MODULE is null.
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*
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* This interface should be called to allocate a Media Device when multiple
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* drivers share usb_device and the media device. This interface allocates
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* &media_device structure and calls media_device_usb_init() to initialize
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* it.
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*
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*/
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struct media_device *media_device_usb_allocate(struct usb_device *udev,
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const char *module_name,
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struct module *owner);
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/**
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* media_device_delete() - Release media device. Calls kref_put().
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*
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* @mdev: struct &media_device pointer
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* @module_name: should be filled with %KBUILD_MODNAME
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* @owner: struct module pointer %THIS_MODULE for the driver.
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* %THIS_MODULE is null for a built-in driver.
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* It is safe even when %THIS_MODULE is null.
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*
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* This interface should be called to put Media Device Instance kref.
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*/
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void media_device_delete(struct media_device *mdev, const char *module_name,
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struct module *owner);
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#else
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static inline struct media_device *media_device_usb_allocate(
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struct usb_device *udev, const char *module_name,
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struct module *owner)
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{ return NULL; }
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static inline void media_device_delete(
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struct media_device *mdev, const char *module_name,
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struct module *owner) { }
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#endif /* CONFIG_MEDIA_CONTROLLER && CONFIG_USB */
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#endif /* _MEDIA_DEV_ALLOCATOR_H */
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