From 8e4bff4cab0ddac6060645b0715210484d02ff40 Mon Sep 17 00:00:00 2001 From: Yuval Adam <_@yuv.al> Date: Wed, 30 Aug 2017 08:25:59 +0000 Subject: Initial file dump from open source release --- .../DocBook/media/v4l/vidioc-create-bufs.xml | 154 +++++++++++++++++++++ 1 file changed, 154 insertions(+) create mode 100644 Documentation/DocBook/media/v4l/vidioc-create-bufs.xml (limited to 'Documentation/DocBook/media/v4l/vidioc-create-bufs.xml') diff --git a/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml b/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml new file mode 100644 index 00000000..cd994367 --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml @@ -0,0 +1,154 @@ + + + ioctl VIDIOC_CREATE_BUFS + &manvol; + + + + VIDIOC_CREATE_BUFS + Create buffers for Memory Mapped or User Pointer or DMA Buffer + I/O + + + + + + int ioctl + int fd + int request + struct v4l2_create_buffers *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_CREATE_BUFS + + + + argp + + + + + + + + + Description + + + Experimental + This is an experimental + interface and may change in the future. + + + This ioctl is used to create buffers for memory +mapped or user pointer or DMA buffer I/O. It can be used as an alternative or in +addition to the VIDIOC_REQBUFS ioctl, when a tighter +control over buffers is required. This ioctl can be called multiple times to +create buffers of different sizes. + + To allocate device buffers applications initialize relevant fields of +the v4l2_create_buffers structure. They set the +type field in the +&v4l2-format; structure, embedded in this +structure, to the respective stream or buffer type. +count must be set to the number of required buffers. +memory specifies the required I/O method. The +format field shall typically be filled in using +either the VIDIOC_TRY_FMT or +VIDIOC_G_FMT ioctl(). Additionally, applications can adjust +sizeimage fields to fit their specific needs. The +reserved array must be zeroed. + + When the ioctl is called with a pointer to this structure the driver +will attempt to allocate up to the requested number of buffers and store the +actual number allocated and the starting index in the +count and the index fields +respectively. On return count can be smaller than +the number requested. The driver may also increase buffer sizes if required, +however, it will not update sizeimage field values. +The user has to use VIDIOC_QUERYBUF to retrieve that +information. + + + struct <structname>v4l2_create_buffers</structname> + + &cs-str; + + + __u32 + index + The starting buffer index, returned by the driver. + + + __u32 + count + The number of buffers requested or granted. If count == 0, then + VIDIOC_CREATE_BUFS will set index + to the current number of created buffers, and it will check the validity of + memory and format.type. + If those are invalid -1 is returned and errno is set to &EINVAL;, + otherwise VIDIOC_CREATE_BUFS returns 0. It will + never set errno to &EBUSY; in this particular case. + + + __u32 + memory + Applications set this field to +V4L2_MEMORY_MMAP, +V4L2_MEMORY_DMABUF or +V4L2_MEMORY_USERPTR. See + + + &v4l2-format; + format + Filled in by the application, preserved by the driver. + + + __u32 + reserved[8] + A place holder for future extensions. + + + +
+ + + + &return-value; + + + + ENOMEM + + No memory to allocate buffers for memory +mapped I/O. + + + + EINVAL + + The buffer type (type field) or the +requested I/O method (memory) is not +supported. + + + + + -- cgit v1.3.1