diff options
Diffstat (limited to 'Documentation/DocBook/media/v4l/vidioc-create-bufs.xml')
| -rw-r--r-- | Documentation/DocBook/media/v4l/vidioc-create-bufs.xml | 28 |
1 files changed, 18 insertions, 10 deletions
diff --git a/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml b/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml index a2474ecb574..cd994367243 100644 --- a/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml +++ b/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml @@ -6,7 +6,8 @@ <refnamediv> <refname>VIDIOC_CREATE_BUFS</refname> - <refpurpose>Create buffers for Memory Mapped or User Pointer I/O</refpurpose> + <refpurpose>Create buffers for Memory Mapped or User Pointer or DMA Buffer + I/O</refpurpose> </refnamediv> <refsynopsisdiv> @@ -55,16 +56,16 @@ </note> <para>This ioctl is used to create buffers for <link linkend="mmap">memory -mapped</link> or <link linkend="userp">user pointer</link> -I/O. It can be used as an alternative or in addition to the -<constant>VIDIOC_REQBUFS</constant> ioctl, when a tighter control over buffers -is required. This ioctl can be called multiple times to create buffers of -different sizes.</para> +mapped</link> or <link linkend="userp">user pointer</link> or <link +linkend="dmabuf">DMA buffer</link> I/O. It can be used as an alternative or in +addition to the <constant>VIDIOC_REQBUFS</constant> ioctl, when a tighter +control over buffers is required. This ioctl can be called multiple times to +create buffers of different sizes.</para> <para>To allocate device buffers applications initialize relevant fields of the <structname>v4l2_create_buffers</structname> structure. They set the <structfield>type</structfield> field in the -<structname>v4l2_format</structname> structure, embedded in this +&v4l2-format; structure, embedded in this structure, to the respective stream or buffer type. <structfield>count</structfield> must be set to the number of required buffers. <structfield>memory</structfield> specifies the required I/O method. The @@ -97,18 +98,25 @@ information.</para> <row> <entry>__u32</entry> <entry><structfield>count</structfield></entry> - <entry>The number of buffers requested or granted.</entry> + <entry>The number of buffers requested or granted. If count == 0, then + <constant>VIDIOC_CREATE_BUFS</constant> will set <structfield>index</structfield> + to the current number of created buffers, and it will check the validity of + <structfield>memory</structfield> and <structfield>format.type</structfield>. + If those are invalid -1 is returned and errno is set to &EINVAL;, + otherwise <constant>VIDIOC_CREATE_BUFS</constant> returns 0. It will + never set errno to &EBUSY; in this particular case.</entry> </row> <row> <entry>__u32</entry> <entry><structfield>memory</structfield></entry> <entry>Applications set this field to -<constant>V4L2_MEMORY_MMAP</constant> or +<constant>V4L2_MEMORY_MMAP</constant>, +<constant>V4L2_MEMORY_DMABUF</constant> or <constant>V4L2_MEMORY_USERPTR</constant>. See <xref linkend="v4l2-memory" /></entry> </row> <row> - <entry>struct v4l2_format</entry> + <entry>&v4l2-format;</entry> <entry><structfield>format</structfield></entry> <entry>Filled in by the application, preserved by the driver.</entry> </row> |