From 19b6ef51640fb35666884c7b577b1a24a4be8e34 Mon Sep 17 00:00:00 2001 From: Tomasz Stanislawski Date: Thu, 14 Jun 2012 11:32:22 -0300 Subject: [media] Documentation: media: description of DMABUF exporting in V4L2 This patch adds description and usage examples for exporting DMABUF file descriptor in V4L2. Signed-off-by: Tomasz Stanislawski Signed-off-by: Kyungmin Park Acked-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- Documentation/DocBook/media/v4l/vidioc-expbuf.xml | 212 ++++++++++++++++++++++ 1 file changed, 212 insertions(+) create mode 100644 Documentation/DocBook/media/v4l/vidioc-expbuf.xml (limited to 'Documentation/DocBook/media/v4l/vidioc-expbuf.xml') diff --git a/Documentation/DocBook/media/v4l/vidioc-expbuf.xml b/Documentation/DocBook/media/v4l/vidioc-expbuf.xml new file mode 100644 index 000000000000..72dfbd20a802 --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-expbuf.xml @@ -0,0 +1,212 @@ + + + + ioctl VIDIOC_EXPBUF + &manvol; + + + + VIDIOC_EXPBUF + Export a buffer as a DMABUF file descriptor. + + + + + + int ioctl + int fd + int request + struct v4l2_exportbuffer *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_EXPBUF + + + + argp + + + + + + + + + Description + + + Experimental + This is an experimental + interface and may change in the future. + + +This ioctl is an extension to the memory +mapping I/O method, therefore it is available only for +V4L2_MEMORY_MMAP buffers. It can be used to export a +buffer as a DMABUF file at any time after buffers have been allocated with the +&VIDIOC-REQBUFS; ioctl. + + To export a buffer, applications fill &v4l2-exportbuffer;. The + type field is set to the same buffer type as was +previously used with &v4l2-requestbuffers; type . +Applications must also set the index field. Valid +index numbers range from zero to the number of buffers allocated with +&VIDIOC-REQBUFS; (&v4l2-requestbuffers; count ) +minus one. For the multi-planar API, applications set the plane + field to the index of the plane to be exported. Valid planes +range from zero to the maximal number of valid planes for the currently active +format. For the single-planar API, applications must set plane + to zero. Additional flags may be posted in the +flags field. Refer to a manual for open() for details. +Currently only O_CLOEXEC is supported. All other fields must be set to zero. +In the case of multi-planar API, every plane is exported separately using +multiple VIDIOC_EXPBUF calls. + + After calling VIDIOC_EXPBUF the fd + field will be set by a driver. This is a DMABUF file +descriptor. The application may pass it to other DMABUF-aware devices. Refer to +DMABUF importing for details about importing +DMABUF files into V4L2 nodes. It is recommended to close a DMABUF file when it +is no longer used to allow the associated memory to be reclaimed. + + + +
+ Examples + + + Exporting a buffer. + +int buffer_export(int v4lfd, &v4l2-buf-type; bt, int index, int *dmafd) +{ + &v4l2-exportbuffer; expbuf; + + memset(&expbuf, 0, sizeof(expbuf)); + expbuf.type = bt; + expbuf.index = index; + if (ioctl(v4lfd, &VIDIOC-EXPBUF;, &expbuf) == -1) { + perror("VIDIOC_EXPBUF"); + return -1; + } + + *dmafd = expbuf.fd; + + return 0; +} + + + + + Exporting a buffer using the multi-planar API. + +int buffer_export_mp(int v4lfd, &v4l2-buf-type; bt, int index, + int dmafd[], int n_planes) +{ + int i; + + for (i = 0; i < n_planes; ++i) { + &v4l2-exportbuffer; expbuf; + + memset(&expbuf, 0, sizeof(expbuf)); + expbuf.type = bt; + expbuf.index = index; + expbuf.plane = i; + if (ioctl(v4lfd, &VIDIOC-EXPBUF;, &expbuf) == -1) { + perror("VIDIOC_EXPBUF"); + while (i) + close(dmafd[--i]); + return -1; + } + dmafd[i] = expbuf.fd; + } + + return 0; +} + + +
+ + + + + struct <structname>v4l2_exportbuffer</structname> + + &cs-str; + + + __u32 + type + Type of the buffer, same as &v4l2-format; +type or &v4l2-requestbuffers; +type, set by the application. See + + + __u32 + index + Number of the buffer, set by the application. This field is +only used for memory mapping I/O and can range from +zero to the number of buffers allocated with the &VIDIOC-REQBUFS; and/or +&VIDIOC-CREATE-BUFS; ioctls. + + + __u32 + plane + Index of the plane to be exported when using the +multi-planar API. Otherwise this value must be set to zero. + + + __u32 + flags + Flags for the newly created file, currently only +O_CLOEXEC is supported, refer to the manual of open() for more +details. + + + __s32 + fd + The DMABUF file descriptor associated with a buffer. Set by + the driver. + + + __u32 + reserved[11] + Reserved field for future use. Must be set to zero. + + + +
+ + + + + &return-value; + + + EINVAL + + A queue is not in MMAP mode or DMABUF exporting is not +supported or flags or type + or index or plane + fields are invalid. + + + + + + -- cgit v1.2.3