linux-3.3/Documentation/media-framework.txt

9 ------------
12 Documentation/DocBook/media/v4l/media-controller.xml. This document will focus
13 on the kernel-side implementation of the media framework.
17 ---------------------------
27 in a System-on-Chip image processing pipeline), DMA channels or physical
35 A link is a point-to-point oriented connection between two pads, either
41 ------------
44 include/media/media-device.h. Allocation of the structure is handled by the
46 larger driver-specific structure.
55  - dev must point to the parent device (usually a pci_dev, usb_interface or
58  - model must be filled with the device model name as a NUL-terminated UTF-8
59    string. The device/model revision must not be stored in this field.
63  - serial is a unique serial number stored as a NUL-terminated ASCII string.
67  - bus_info represents the location of the device in the system as a
68    NUL-terminated ASCII string. For PCI/PCIe devices bus_info must be set to
74  - hw_revision is the hardware device revision in a driver-specific format.
78  - driver_version is formatted with the KERNEL_VERSION macro. The version
83 Upon successful registration a character device named media[0-9]+ is created.
95 ------------------------
97 - Entities
100 include/media/media-entity.h. The structure is usually embedded into a
101 higher-level structure, such as a v4l2_subdev or video_device instance,
111 higher-level standard structures can have some of those fields set by the
112 higher-level framework.
114 As the number of pads is known in advance, the pads array is not allocated
116 pads array in a driver-specific structure, avoiding dynamic allocation.
118 Drivers must set the direction of every pad in the pads array before calling
123 pre-allocates a number of links equal to the number of pads plus an optional
124 number of extra links. The links array will be reallocated if it grows beyond
163 entities to the same non-zero value. An entity group serves no purpose in the
171 	- ALSA, VBI and video nodes that carry the same media stream
172 	- lens and flash controllers associated with a sensor
174 - Pads
177 include/media/media-entity.h. Each entity stores its pads in a pads array
178 managed by the entity driver. Drivers usually embed the array in a
179 driver-specific structure.
181 Pads are identified by their entity and their 0-based index in the pads array.
193 - Links
196 include/media/media-entity.h. Each entity stores all links originating at or
197 targeting any of its pads in a links array. A given link is thus stored
198 twice, once in the source entity and once in the target entity. The array is
199 pre-allocated and grows dynamically as needed.
207 An entry in the link array of each entity is allocated and stores pointers
222 ---------------
227 media_device_for_each_entity macro, defined in include/media/media-device.h.
238 framework provides a depth-first graph traversal API for that purpose.
274 ----------------------------
287 -----------
295 The only configurable property is the ENABLED link flag to enable/disable a
309 is non-immutable. The operation must either configure the hardware or store
314 the link_setup operation must return -EBUSY and can't implicitly disable the
319 ---------------------------
332 in higher-level pipeline structures and can then access the pipeline through
346 Link configuration will fail with -EBUSY by default if either end of the link is