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Diffstat (limited to 'Documentation/media/kapi')
| -rw-r--r-- | Documentation/media/kapi/mc-core.rst | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/Documentation/media/kapi/mc-core.rst b/Documentation/media/kapi/mc-core.rst index f930725e0d6b..05bba0b61748 100644 --- a/Documentation/media/kapi/mc-core.rst +++ b/Documentation/media/kapi/mc-core.rst @@ -259,6 +259,45 @@ 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 the 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. + +The shared media device should stay in registered state until the last +driver unregisters it. In addition, the 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, the allocate API bumps up the refcount and returns the +existing media device. The driver puts the reference back in its disconnect +routine when it calls :c:func:`media_device_delete()`. + +The 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 appropriate media-core routines to manage the shared +media device life-time handling the two states: +1. allocate -> register -> delete +2. get reference to already registered device -> delete + +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. Freeing is +handled by the kref put handler. + +API Definitions +^^^^^^^^^^^^^^^ + .. kernel-doc:: include/media/media-device.h .. kernel-doc:: include/media/media-devnode.h @@ -266,3 +305,5 @@ in the end provide a way to use driver-specific callbacks. .. kernel-doc:: include/media/media-entity.h .. kernel-doc:: include/media/media-request.h + +.. kernel-doc:: include/media/media-dev-allocator.h |