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Diffstat (limited to 'Documentation/DocBook/media/v4l/vidioc-qbuf.xml')
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1 files changed, 0 insertions, 202 deletions
diff --git a/Documentation/DocBook/media/v4l/vidioc-qbuf.xml b/Documentation/DocBook/media/v4l/vidioc-qbuf.xml deleted file mode 100644 index 8b98a0e421fc..000000000000 --- a/Documentation/DocBook/media/v4l/vidioc-qbuf.xml +++ /dev/null @@ -1,202 +0,0 @@ -<refentry id="vidioc-qbuf"> - <refmeta> - <refentrytitle>ioctl VIDIOC_QBUF, VIDIOC_DQBUF</refentrytitle> - &manvol; - </refmeta> - - <refnamediv> - <refname>VIDIOC_QBUF</refname> - <refname>VIDIOC_DQBUF</refname> - <refpurpose>Exchange a buffer with the driver</refpurpose> - </refnamediv> - - <refsynopsisdiv> - <funcsynopsis> - <funcprototype> - <funcdef>int <function>ioctl</function></funcdef> - <paramdef>int <parameter>fd</parameter></paramdef> - <paramdef>int <parameter>request</parameter></paramdef> - <paramdef>struct v4l2_buffer *<parameter>argp</parameter></paramdef> - </funcprototype> - </funcsynopsis> - </refsynopsisdiv> - - <refsect1> - <title>Arguments</title> - - <variablelist> - <varlistentry> - <term><parameter>fd</parameter></term> - <listitem> - <para>&fd;</para> - </listitem> - </varlistentry> - <varlistentry> - <term><parameter>request</parameter></term> - <listitem> - <para>VIDIOC_QBUF, VIDIOC_DQBUF</para> - </listitem> - </varlistentry> - <varlistentry> - <term><parameter>argp</parameter></term> - <listitem> - <para></para> - </listitem> - </varlistentry> - </variablelist> - </refsect1> - - <refsect1> - <title>Description</title> - - <para>Applications call the <constant>VIDIOC_QBUF</constant> ioctl -to enqueue an empty (capturing) or filled (output) buffer in the -driver's incoming queue. The semantics depend on the selected I/O -method.</para> - - <para>To enqueue a buffer applications set the <structfield>type</structfield> -field of a &v4l2-buffer; to the same buffer type as was previously used -with &v4l2-format; <structfield>type</structfield> and &v4l2-requestbuffers; -<structfield>type</structfield>. Applications must also set the -<structfield>index</structfield> field. Valid index numbers range from -zero to the number of buffers allocated with &VIDIOC-REQBUFS; -(&v4l2-requestbuffers; <structfield>count</structfield>) minus one. The -contents of the struct <structname>v4l2_buffer</structname> returned -by a &VIDIOC-QUERYBUF; ioctl will do as well. When the buffer is -intended for output (<structfield>type</structfield> is -<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant>, -<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant>, or -<constant>V4L2_BUF_TYPE_VBI_OUTPUT</constant>) applications must also -initialize the <structfield>bytesused</structfield>, -<structfield>field</structfield> and -<structfield>timestamp</structfield> fields, see <xref -linkend="buffer" /> for details. -Applications must also set <structfield>flags</structfield> to 0. -The <structfield>reserved2</structfield> and -<structfield>reserved</structfield> fields must be set to 0. When using -the <link linkend="planar-apis">multi-planar API</link>, the -<structfield>m.planes</structfield> field must contain a userspace pointer -to a filled-in array of &v4l2-plane; and the <structfield>length</structfield> -field must be set to the number of elements in that array. -</para> - - <para>To enqueue a <link linkend="mmap">memory mapped</link> -buffer applications set the <structfield>memory</structfield> -field to <constant>V4L2_MEMORY_MMAP</constant>. When -<constant>VIDIOC_QBUF</constant> is called with a pointer to this -structure the driver sets the -<constant>V4L2_BUF_FLAG_MAPPED</constant> and -<constant>V4L2_BUF_FLAG_QUEUED</constant> flags and clears the -<constant>V4L2_BUF_FLAG_DONE</constant> flag in the -<structfield>flags</structfield> field, or it returns an -&EINVAL;.</para> - - <para>To enqueue a <link linkend="userp">user pointer</link> -buffer applications set the <structfield>memory</structfield> -field to <constant>V4L2_MEMORY_USERPTR</constant>, the -<structfield>m.userptr</structfield> field to the address of the -buffer and <structfield>length</structfield> to its size. When the multi-planar -API is used, <structfield>m.userptr</structfield> and -<structfield>length</structfield> members of the passed array of &v4l2-plane; -have to be used instead. When <constant>VIDIOC_QBUF</constant> is called with -a pointer to this structure the driver sets the -<constant>V4L2_BUF_FLAG_QUEUED</constant> flag and clears the -<constant>V4L2_BUF_FLAG_MAPPED</constant> and -<constant>V4L2_BUF_FLAG_DONE</constant> flags in the -<structfield>flags</structfield> field, or it returns an error code. -This ioctl locks the memory pages of the buffer in physical memory, -they cannot be swapped out to disk. Buffers remain locked until -dequeued, until the &VIDIOC-STREAMOFF; or &VIDIOC-REQBUFS; ioctl is -called, or until the device is closed.</para> - - <para>To enqueue a <link linkend="dmabuf">DMABUF</link> buffer applications -set the <structfield>memory</structfield> field to -<constant>V4L2_MEMORY_DMABUF</constant> and the <structfield>m.fd</structfield> -field to a file descriptor associated with a DMABUF buffer. When the -multi-planar API is used the <structfield>m.fd</structfield> fields of the -passed array of &v4l2-plane; have to be used instead. When -<constant>VIDIOC_QBUF</constant> is called with a pointer to this structure the -driver sets the <constant>V4L2_BUF_FLAG_QUEUED</constant> flag and clears the -<constant>V4L2_BUF_FLAG_MAPPED</constant> and -<constant>V4L2_BUF_FLAG_DONE</constant> flags in the -<structfield>flags</structfield> field, or it returns an error code. This -ioctl locks the buffer. Locking a buffer means passing it to a driver for a -hardware access (usually DMA). If an application accesses (reads/writes) a -locked buffer then the result is undefined. Buffers remain locked until -dequeued, until the &VIDIOC-STREAMOFF; or &VIDIOC-REQBUFS; ioctl is called, or -until the device is closed.</para> - - <para>Applications call the <constant>VIDIOC_DQBUF</constant> -ioctl to dequeue a filled (capturing) or displayed (output) buffer -from the driver's outgoing queue. They just set the -<structfield>type</structfield>, <structfield>memory</structfield> -and <structfield>reserved</structfield> -fields of a &v4l2-buffer; as above, when <constant>VIDIOC_DQBUF</constant> -is called with a pointer to this structure the driver fills the -remaining fields or returns an error code. The driver may also set -<constant>V4L2_BUF_FLAG_ERROR</constant> in the <structfield>flags</structfield> -field. It indicates a non-critical (recoverable) streaming error. In such case -the application may continue as normal, but should be aware that data in the -dequeued buffer might be corrupted. When using the multi-planar API, the -planes array must be passed in as well.</para> - - <para>By default <constant>VIDIOC_DQBUF</constant> blocks when no -buffer is in the outgoing queue. When the -<constant>O_NONBLOCK</constant> flag was given to the &func-open; -function, <constant>VIDIOC_DQBUF</constant> returns immediately -with an &EAGAIN; when no buffer is available.</para> - - <para>The <structname>v4l2_buffer</structname> structure is -specified in <xref linkend="buffer" />.</para> - </refsect1> - - <refsect1> - &return-value; - - <variablelist> - <varlistentry> - <term><errorcode>EAGAIN</errorcode></term> - <listitem> - <para>Non-blocking I/O has been selected using -<constant>O_NONBLOCK</constant> and no buffer was in the outgoing -queue.</para> - </listitem> - </varlistentry> - <varlistentry> - <term><errorcode>EINVAL</errorcode></term> - <listitem> - <para>The buffer <structfield>type</structfield> is not -supported, or the <structfield>index</structfield> is out of bounds, -or no buffers have been allocated yet, or the -<structfield>userptr</structfield> or -<structfield>length</structfield> are invalid.</para> - </listitem> - </varlistentry> - <varlistentry> - <term><errorcode>EIO</errorcode></term> - <listitem> - <para><constant>VIDIOC_DQBUF</constant> failed due to an -internal error. Can also indicate temporary problems like signal -loss. Note the driver might dequeue an (empty) buffer despite -returning an error, or even stop capturing. Reusing such buffer may be unsafe -though and its details (e.g. <structfield>index</structfield>) may not be -returned either. It is recommended that drivers indicate recoverable errors -by setting the <constant>V4L2_BUF_FLAG_ERROR</constant> and returning 0 instead. -In that case the application should be able to safely reuse the buffer and -continue streaming. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term><errorcode>EPIPE</errorcode></term> - <listitem> - <para><constant>VIDIOC_DQBUF</constant> returns this on an empty -capture queue for mem2mem codecs if a buffer with the -<constant>V4L2_BUF_FLAG_LAST</constant> was already dequeued and no new buffers -are expected to become available. - </para> - </listitem> - </varlistentry> - </variablelist> - </refsect1> -</refentry> |