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| /Documentation/userspace-api/media/v4l/ |
| D | mmap.rst | 18 Streaming is an I/O method where only pointers to buffers are exchanged
20 mapping is primarily intended to map buffers in device memory into the
24 drivers support streaming as well, allocating buffers in DMA-able main
27 A driver can support many sets of buffers. Each set is identified by a
32 To allocate device buffers applications call the
34 of buffers and buffer type, for example ``V4L2_BUF_TYPE_VIDEO_CAPTURE``.
35 This ioctl can also be used to change the number of buffers or to free
36 the allocated memory, provided none of the buffers are still mapped.
38 Before applications can access the buffers they must map them into their
40 location of the buffers in device memory can be determined with the
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| D | userp.rst | 19 methods. Buffers (planes) are allocated by the application itself, and
26 No buffers (planes) are allocated beforehand, consequently they are not
27 indexed and cannot be queried like mapped buffers with the
51 :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl. Although buffers are commonly
60 Filled or displayed buffers are dequeued with the
66 Applications must take care not to free buffers without dequeuing.
67 Firstly, the buffers remain locked for longer, wasting physical memory.
73 buffers, to start capturing and enter the read loop. Here the
76 and enqueue buffers, when enough buffers are stacked up output is
78 buffers it must wait until an empty buffer can be dequeued and reused.
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| D | dev-decoder.rst | 12 from the client to process these buffers.
50 the destination buffer queue; for decoders, the queue of buffers containing
51 decoded frames; for encoders, the queue of buffers containing an encoded
54 into ``CAPTURE`` buffers.
78 ``OUTPUT`` buffers must be queued by the client in decode order; for
79 encoders ``CAPTURE`` buffers must be returned by the encoder in decode order.
86 buffers must be queued by the client in display order; for decoders,
87 ``CAPTURE`` buffers must be returned by the decoder in display order.
110 the source buffer queue; for decoders, the queue of buffers containing
111 an encoded bytestream; for encoders, the queue of buffers containing raw
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| D | vidioc-reqbufs.rst | 36 Memory mapped buffers are located in device memory and must be allocated
38 space. User buffers are allocated by applications themselves, and this
40 to setup some internal structures. Similarly, DMABUF buffers are
45 To allocate device buffers applications initialize all fields of the
48 the desired number of buffers, ``memory`` must be set to the requested
51 allocate the requested number of buffers and it stores the actual number
54 number is also possible when the driver requires more buffers to
56 buffers, one displayed and one filled by the application.
62 buffers. Note that if any buffers are still mapped or exported via DMABUF,
66 If ``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS`` is set, then these buffers are
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| D | capture.c.rst | 51 struct buffer *buffers;
91 if (-1 == read(fd, buffers[0].start, buffers[0].length)) {
106 process_image(buffers[0].start, buffers[0].length);
132 process_image(buffers[buf.index].start, buf.bytesused);
160 if (buf.m.userptr == (unsigned long)buffers[i].start
161 && buf.length == buffers[i].length)
268 buf.m.userptr = (unsigned long)buffers[i].start;
269 buf.length = buffers[i].length;
287 free(buffers[0].start);
292 if (-1 == munmap(buffers[i].start, buffers[i].length))
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| D | vidioc-create-bufs.rst | 13 VIDIOC_CREATE_BUFS - Create buffers for Memory Mapped or User Pointer or DMA Buffer I/O
34 This ioctl is used to create buffers for :ref:`memory mapped <mmap>`
38 over buffers is required. This ioctl can be called multiple times to
39 create buffers of different sizes.
41 To allocate the device buffers applications must initialize the relevant
43 ``count`` field must be set to the number of requested buffers, the
47 The ``format`` field specifies the image format that the buffers must be
54 sizes (for multi-planar formats) will be used for the allocated buffers.
58 The buffers created by this ioctl will have as minimum size the size
68 will attempt to allocate up to the requested number of buffers and store
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| D | dmabuf.rst | 10 The DMABUF framework provides a generic method for sharing buffers
19 exporting V4L2 buffers as DMABUF file descriptors.
25 importing DMA buffers through DMABUF file descriptors is supported is
29 This I/O method is dedicated to sharing DMA buffers between different
31 DRM). Buffers (planes) are allocated by a driver on behalf of an
32 application. Next, these buffers are exported to the application as file
63 buffers, every plane can be associated with a different DMABUF
64 descriptor. Although buffers are commonly cycled, applications can pass
121 Captured or displayed buffers are dequeued with the
129 buffers, to start capturing and enter the read loop. Here the
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| D | dev-encoder.rst | 157 desired size of ``CAPTURE`` buffers; the encoder may adjust it to
169 adjusted size of ``CAPTURE`` buffers.
307 coded video. It does *not* set the rate at which buffers arrive on the
365 buffers to be aligned to 1920x1088 for codecs with 16x16 macroblock
375 7. Allocate buffers for both ``OUTPUT`` and ``CAPTURE`` via
381 requested number of buffers to allocate; greater than zero.
393 actual number of buffers allocated.
397 The actual number of allocated buffers may differ from the ``count``
403 To allocate more than the minimum number of OUTPUT buffers (for pipeline
405 control to get the minimum number of buffers required, and pass the
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| D | vidioc-streamon.rst | 43 Capture hardware is disabled and no input buffers are filled (if there
44 are any empty buffers in the incoming queue) until ``VIDIOC_STREAMON``
52 If ``VIDIOC_STREAMON`` fails then any already queued buffers will remain
56 in progress, unlocks any user pointer buffers locked in physical memory,
57 and it removes all buffers from the incoming and outgoing queues. That
64 If buffers have been queued with :ref:`VIDIOC_QBUF` and
66 ``VIDIOC_STREAMON``, then those queued buffers will also be removed from
78 but ``VIDIOC_STREAMOFF`` will return queued buffers to their starting
96 The buffer ``type`` is not supported, or no buffers have been
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| D | dev-stateless-decoder.rst | 100 destination buffers parsed/decoded from the bytestream.
167 to obtain up-to-date information about the buffers size and layout.
169 6. Allocate source (bytestream) buffers via :c:func:`VIDIOC_REQBUFS` on
175 requested number of buffers to allocate; greater than zero.
186 actual number of buffers allocated.
189 minimum of required number of ``OUTPUT`` buffers for the given format and
191 to get the actual number of buffers allocated.
193 7. Allocate destination (raw format) buffers via :c:func:`VIDIOC_REQBUFS` on the
199 requested number of buffers to allocate; greater than zero. The client
200 is responsible for deducing the minimum number of buffers required
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| D | v4l2grab.c.rst | 67 struct buffer *buffers;
96 buffers = calloc(req.count, sizeof(*buffers));
106 buffers[n_buffers].length = buf.length;
107 buffers[n_buffers].start = v4l2_mmap(NULL, buf.length,
111 if (MAP_FAILED == buffers[n_buffers].start) {
156 fwrite(buffers[buf.index].start, buf.bytesused, 1, fout);
165 v4l2_munmap(buffers[i].start, buffers[i].length);
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| D | func-read.rst | 58 single or multiple buffers and discarding the oldest or newest frames
59 once the internal buffers are filled.
84 buffers, automatically advancing to the next free buffer. This allows
85 continuous capturing when the application can empty the buffers fast
86 enough. Again, the behavior when the driver runs out of free buffers
89 Applications can get and set the number of buffers used internally by
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| /Documentation/userspace-api/media/dvb/ |
| D | dmx-reqbufs.rst | 38 Memory mapped buffers are located in device memory and must be allocated
40 space. User buffers are allocated by applications themselves, and this
42 to setup some internal structures. Similarly, DMABUF buffers are
47 To allocate device buffers applications initialize all fields of the
49 to the desired number of buffers, and ``size`` to the size of each
53 attempt to allocate the requested number of buffers and it stores the actual
55 number is also possible when the driver requires more buffers to
63 buffers, however this cannot succeed when any buffers are still mapped.
64 A ``count`` value of zero frees all buffers, after aborting or finishing
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| /Documentation/driver-api/media/ |
| D | v4l2-videobuf.rst | 21 and user space. It handles the allocation and management of buffers for
34 Not all video devices use the same kind of buffers. In fact, there are (at
37 - Buffers which are scattered in both the physical and (kernel) virtual
38 address spaces. (Almost) all user-space buffers are like this, but it
39 makes great sense to allocate kernel-space buffers this way as well when
44 - Buffers which are physically scattered, but which are virtually
45 contiguous; buffers allocated with vmalloc(), in other words. These
46 buffers are just as hard to use for DMA operations, but they can be
48 buffers are convenient.
50 - Buffers which are physically contiguous. Allocation of this kind of
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| /Documentation/ABI/testing/ |
| D | sysfs-kernel-dmabuf-buffers | 1 What: /sys/kernel/dmabuf/buffers
5 Description: The /sys/kernel/dmabuf/buffers directory contains a
7 /sys/kernel/dmabuf/buffers/<inode_number> will contain the
12 What: /sys/kernel/dmabuf/buffers/<inode_number>/exporter_name
19 What: /sys/kernel/dmabuf/buffers/<inode_number>/size
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| /Documentation/admin-guide/media/ |
| D | cafe_ccic.rst | 37 buffers until the time comes to transfer data. If this option is set,
38 then worst-case-sized buffers will be allocated at module load time.
42 - dma_buf_size: The size of DMA buffers to allocate. Note that this
43 option is only consulted for load-time allocation; when buffers are
48 buffers. Normally, the driver tries to use three buffers; on faster
51 - min_buffers: The minimum number of streaming I/O buffers that the driver
56 - max_buffers: The maximum number of streaming I/O buffers; default is
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| /Documentation/gpu/ |
| D | xen-front.rst | 9 Driver modes of operation in terms of display buffers used
13 :doc: Driver modes of operation in terms of display buffers used
15 Buffers allocated by the frontend driver
19 :doc: Buffers allocated by the frontend driver
21 Buffers allocated by the backend
25 :doc: Buffers allocated by the backend
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| /Documentation/filesystems/ |
| D | relay.rst | 12 as a set of per-cpu kernel buffers ('channel buffers'), each
14 clients write into the channel buffers using efficient write
19 are associated with the channel buffers using the API described below.
21 The format of the data logged into the channel buffers is completely
36 sub-buffers. Messages are written to the first sub-buffer until it is
38 the next (if available). Messages are never split across sub-buffers.
60 read sub-buffers; thus in cases where read(2) is being used to drain
61 the channel buffers, special-purpose communication between kernel and
96 allowing both to convey the state of buffers (full, empty, amount of
98 consumes the read sub-buffers; thus in cases where read(2) is being
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| /Documentation/userspace-api/media/mediactl/ |
| D | request-api.rst | 21 on the media pipeline, reconfigure it for the next frame, queue the buffers to
28 specific buffers. This allows user-space to schedule several tasks ("requests")
59 instead of being immediately applied, and buffers queued to a request do not
65 Once the configuration and buffers of the request are specified, it can be
72 output buffers, not for capture buffers. Attempting to add a capture buffer
77 buffers are processed. Media controller drivers do a best effort implementation
82 It is not allowed to mix queuing requests with directly queuing buffers:
99 once all its associated buffers are available for dequeuing and all the
102 dequeue its buffers: buffers that are available halfway through a request can
135 to queue many such buffers in advance. It can also take advantage of requests'
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| /Documentation/driver-api/usb/ |
| D | dma.rst | 12 though they still must provide DMA-ready buffers (see
18 - New calls enable DMA-aware drivers, letting them allocate dma buffers and
19 manage dma mappings for existing dma-ready buffers (see below).
88 Working with existing buffers
91 Existing buffers aren't usable for DMA without first being mapped into the
92 DMA address space of the device. However, most buffers passed to your
113 buffers, synchronizing their safe re-use. (If there's no re-use, then let
131 They cannot be used for setup_packet buffers in control requests.
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| /Documentation/x86/ |
| D | mds.rst | 10 on internal buffers in Intel CPUs. The variants are:
21 buffers are partitioned between Hyper-Threads so cross thread forwarding is
25 MFBDS leaks Fill Buffer Entries. Fill buffers are used internally to manage
27 to a memory or I/O operation. Fill buffers can forward data to a load
31 be exploited under certain conditions. Fill buffers are shared between
74 thread case (SMT off): Force the CPU to clear the affected buffers.
78 the affected CPU buffers when the VERW instruction is executed.
104 hope that it might actually clear the buffers. The state is reflected
139 When transitioning from kernel to user space the CPU buffers are flushed
157 When a CPU goes idle and enters a C-State the CPU buffers need to be
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| /Documentation/driver-api/iio/ |
| D | index.rst | 15 buffers
17 triggered-buffers
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| /Documentation/admin-guide/hw-vuln/ |
| D | processor_mmio_stale_data.rst | 12 stale data into core fill buffers where the data can subsequently be inferred
29 Stale data may propagate from fill buffers (FB) into the non-coherent portion
42 response and transaction buffers may now reside in a core fill buffer.
61 processors affected by FBSDP, this may expose stale data from the fill buffers
64 Shared Buffers Data Sampling (SBDS) (CVE-2022-21125)
67 into client core fill buffers, processors affected by MFBDS can leak data from
71 Shared Buffers Data Read (SBDR) (CVE-2022-21123)
111 clear the CPU fill buffers via VERW instruction.
123 Shared Buffers Data Read (SBDR) vulnerability or the sideband stale
153 same mitigation strategy to force the CPU to clear the affected buffers before
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| D | tsx_async_abort.rst | 7 data which is available in various CPU internal buffers by using asynchronous
39 data into temporary microarchitectural structures (buffers). The data in
40 those buffers can be forwarded to load operations as an optimization.
54 executed loads may read data from those internal buffers and pass it to dependent
58 Because the buffers are potentially shared between Hyper-Threads cross
63 which in turn potenitally leaks data stored in the buffers.
100 * - 'Vulnerable: Clear CPU buffers attempted, no microcode'
101 - The system tries to clear the buffers but the microcode might not support the operation.
102 * - 'Mitigation: Clear CPU buffers'
103 - The microcode has been updated to clear the buffers. TSX is still enabled.
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| /Documentation/i2c/ |
| D | dma-considerations.rst | 19 safe buffers always, because USB requires it.
32 buffers in kernel space are always DMA capable. Also, when the core emulates
33 SMBus transactions via I2C, the buffers for block transfers are DMA safe. Users
36 know their buffers are DMA safe. Users of i2c_transfer() must set the
64 reusing pre-allocated buffers), you are free to implement your own.
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