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authorShuah Khan <shuah@kernel.org>2019-04-02 02:40:19 +0200
committerMauro Carvalho Chehab <mchehab+samsung@kernel.org>2019-04-22 17:18:26 +0200
commit6e1d824e7a1d324f7fdd276fb7133013109d3764 (patch)
treedd135d8fd4f43d2375e1716eb0b6cb0dfc055ee7 /include/media
parentmedia: stm32-dcmi: fix crash when subdev do not expose any formats (diff)
downloadlinux-6e1d824e7a1d324f7fdd276fb7133013109d3764.tar.xz
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media: Media Device Allocator API
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>
Diffstat (limited to 'include/media')
-rw-r--r--include/media/media-dev-allocator.h63
1 files changed, 63 insertions, 0 deletions
diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h
new file mode 100644
index 000000000000..b35ea6062596
--- /dev/null
+++ b/include/media/media-dev-allocator.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * media-dev-allocator.h - Media Controller Device Allocator API
+ *
+ * Copyright (c) 2019 Shuah Khan <shuah@kernel.org>
+ *
+ * Credits: Suggested by Laurent Pinchart <laurent.pinchart@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_ALLOCATOR_H
+#define _MEDIA_DEV_ALLOCATOR_H
+
+struct usb_device;
+
+#if defined(CONFIG_MEDIA_CONTROLLER) && defined(CONFIG_USB)
+/**
+ * media_device_usb_allocate() - Allocate and return struct &media device
+ *
+ * @udev: struct &usb_device pointer
+ * @module_name: should be filled with %KBUILD_MODNAME
+ * @owner: struct module pointer %THIS_MODULE for the driver.
+ * %THIS_MODULE is null for a built-in driver.
+ * It is safe even when %THIS_MODULE is null.
+ *
+ * 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 structure and calls media_device_usb_init() to initialize
+ * it.
+ *
+ */
+struct media_device *media_device_usb_allocate(struct usb_device *udev,
+ const char *module_name,
+ struct module *owner);
+/**
+ * media_device_delete() - Release media device. Calls kref_put().
+ *
+ * @mdev: struct &media_device pointer
+ * @module_name: should be filled with %KBUILD_MODNAME
+ * @owner: struct module pointer %THIS_MODULE for the driver.
+ * %THIS_MODULE is null for a built-in driver.
+ * It is safe even when %THIS_MODULE is null.
+ *
+ * This interface should be called to put Media Device Instance kref.
+ */
+void media_device_delete(struct media_device *mdev, const char *module_name,
+ struct module *owner);
+#else
+static inline struct media_device *media_device_usb_allocate(
+ struct usb_device *udev, const char *module_name,
+ struct module *owner)
+ { return NULL; }
+static inline void media_device_delete(
+ struct media_device *mdev, const char *module_name,
+ struct module *owner) { }
+#endif /* CONFIG_MEDIA_CONTROLLER && CONFIG_USB */
+#endif /* _MEDIA_DEV_ALLOCATOR_H */