From 55093284fb6f9009a339e522773417bdd54ec144 Mon Sep 17 00:00:00 2001 From: Guennadi Liakhovetski Date: Wed, 28 Sep 2011 08:10:58 -0300 Subject: [media] V4L: document the new VIDIOC_CREATE_BUFS and VIDIOC_PREPARE_BUF ioctl()s [mchehab@redhat.com: remove emacs format crap at the end of the new files] Signed-off-by: Guennadi Liakhovetski Signed-off-by: Mauro Carvalho Chehab --- Documentation/DocBook/media/v4l/compat.xml | 3 + Documentation/DocBook/media/v4l/io.xml | 27 ++++ Documentation/DocBook/media/v4l/v4l2.xml | 2 + .../DocBook/media/v4l/vidioc-create-bufs.xml | 139 +++++++++++++++++++++ .../DocBook/media/v4l/vidioc-prepare-buf.xml | 88 +++++++++++++ 5 files changed, 259 insertions(+) create mode 100644 Documentation/DocBook/media/v4l/vidioc-create-bufs.xml create mode 100644 Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml (limited to 'Documentation') diff --git a/Documentation/DocBook/media/v4l/compat.xml b/Documentation/DocBook/media/v4l/compat.xml index 91410b6e7e08..b68698f96e7f 100644 --- a/Documentation/DocBook/media/v4l/compat.xml +++ b/Documentation/DocBook/media/v4l/compat.xml @@ -2486,6 +2486,9 @@ ioctls. Flash API. + + &VIDIOC-CREATE-BUFS; and &VIDIOC-PREPARE-BUF; ioctls. + diff --git a/Documentation/DocBook/media/v4l/io.xml b/Documentation/DocBook/media/v4l/io.xml index c57d1ec6291c..3f47df1aa54a 100644 --- a/Documentation/DocBook/media/v4l/io.xml +++ b/Documentation/DocBook/media/v4l/io.xml @@ -927,6 +927,33 @@ ioctl is called. Applications set or clear this flag before calling the VIDIOC_QBUF ioctl. + + V4L2_BUF_FLAG_PREPARED + 0x0400 + The buffer has been prepared for I/O and can be queued by the +application. Drivers set or clear this flag when the +VIDIOC_QUERYBUF, VIDIOC_PREPARE_BUF, VIDIOC_QBUF or VIDIOC_DQBUF ioctl is called. + + + V4L2_BUF_FLAG_NO_CACHE_INVALIDATE + 0x0400 + Caches do not have to be invalidated for this buffer. +Typically applications shall use this flag if the data captured in the buffer +is not going to be touched by the CPU, instead the buffer will, probably, be +passed on to a DMA-capable hardware unit for further processing or output. + + + + V4L2_BUF_FLAG_NO_CACHE_CLEAN + 0x0800 + Caches do not have to be cleaned for this buffer. +Typically applications shall use this flag for output buffers if the data +in this buffer has not been created by the CPU but by some DMA-capable unit, +in which case caches have not been used. + diff --git a/Documentation/DocBook/media/v4l/v4l2.xml b/Documentation/DocBook/media/v4l/v4l2.xml index 40132c277647..2ab365c10fb9 100644 --- a/Documentation/DocBook/media/v4l/v4l2.xml +++ b/Documentation/DocBook/media/v4l/v4l2.xml @@ -469,6 +469,7 @@ and discussions on the V4L mailing list. &sub-close; &sub-ioctl; + &sub-create-bufs; &sub-cropcap; &sub-dbg-g-chip-ident; &sub-dbg-g-register; @@ -511,6 +512,7 @@ and discussions on the V4L mailing list. &sub-queryctrl; &sub-query-dv-preset; &sub-querystd; + &sub-prepare-buf; &sub-reqbufs; &sub-s-hw-freq-seek; &sub-streamon; 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 000000000000..73ae8a6cd004 --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml @@ -0,0 +1,139 @@ + + + ioctl VIDIOC_CREATE_BUFS + &manvol; + + + + VIDIOC_CREATE_BUFS + Create buffers for Memory Mapped or User Pointer I/O + + + + + + int ioctl + int fd + int request + struct v4l2_create_buffers *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_CREATE_BUFS + + + + argp + + + + + + + + + Description + + This ioctl is used to create buffers for memory +mapped or user pointer +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. + + + &v4l2-memory; + memory + Applications set this field to +V4L2_MEMORY_MMAP or +V4L2_MEMORY_USERPTR. + + + &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. + + + + + diff --git a/Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml b/Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml new file mode 100644 index 000000000000..7bde698760e4 --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml @@ -0,0 +1,88 @@ + + + ioctl VIDIOC_PREPARE_BUF + &manvol; + + + + VIDIOC_PREPARE_BUF + Prepare a buffer for I/O + + + + + + int ioctl + int fd + int request + struct v4l2_buffer *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_PREPARE_BUF + + + + argp + + + + + + + + + Description + + Applications can optionally call the +VIDIOC_PREPARE_BUF ioctl to pass ownership of the buffer +to the driver before actually enqueuing it, using the +VIDIOC_QBUF ioctl, and to prepare it for future I/O. +Such preparations may include cache invalidation or cleaning. Performing them +in advance saves time during the actual I/O. In case such cache operations are +not required, the application can use one of +V4L2_BUF_FLAG_NO_CACHE_INVALIDATE and +V4L2_BUF_FLAG_NO_CACHE_CLEAN flags to skip the respective +step. + + The v4l2_buffer structure is +specified in . + + + + &return-value; + + + + EBUSY + + File I/O is in progress. + + + + EINVAL + + The buffer type is not +supported, or the index is out of bounds, +or no buffers have been allocated yet, or the +userptr or +length are invalid. + + + + + -- cgit v1.2.3