summaryrefslogtreecommitdiff
path: root/Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml
diff options
context:
space:
mode:
authorArtem Bityutskiy <Artem.Bityutskiy@nokia.com>2011-03-25 17:41:20 +0200
committerArtem Bityutskiy <Artem.Bityutskiy@nokia.com>2011-03-25 17:41:20 +0200
commit7bf7e370d5919112c223a269462cd0b546903829 (patch)
tree03ccc715239df14ae168277dbccc9d9cf4d8a2c8 /Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml
parent68b1a1e786f29c900fa1c516a402e24f0ece622a (diff)
parentd39dd11c3e6a7af5c20bfac40594db36cf270f42 (diff)
Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6 into for-linus-1
* 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6: (9356 commits) [media] rc: update for bitop name changes fs: simplify iget & friends fs: pull inode->i_lock up out of writeback_single_inode fs: rename inode_lock to inode_hash_lock fs: move i_wb_list out from under inode_lock fs: move i_sb_list out from under inode_lock fs: remove inode_lock from iput_final and prune_icache fs: Lock the inode LRU list separately fs: factor inode disposal fs: protect inode->i_state with inode->i_lock lib, arch: add filter argument to show_mem and fix private implementations SLUB: Write to per cpu data when allocating it slub: Fix debugobjects with lockless fastpath autofs4: Do not potentially dereference NULL pointer returned by fget() in autofs_dev_ioctl_setpipefd() autofs4 - remove autofs4_lock autofs4 - fix d_manage() return on rcu-walk autofs4 - fix autofs4_expire_indirect() traversal autofs4 - fix dentry leak in autofs4_expire_direct() autofs4 - reinstate last used update on access vfs - check non-mountpoint dentry might block in __follow_mount_rcu() ... NOTE! This merge commit was created to fix compilation error. The block tree was merged upstream and removed the 'elv_queue_empty()' function which the new 'mtdswap' driver is using. So a simple merge of the mtd tree with upstream does not compile. And the mtd tree has already be published, so re-basing it is not an option. To fix this unfortunate situation, I had to merge upstream into the mtd-2.6.git tree without committing, put the fixup patch on top of this, and then commit this. The result is that we do not have commits which do not compile. In other words, this merge commit "merges" 3 things: the MTD tree, the upstream tree, and the fixup patch.
Diffstat (limited to 'Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml')
-rw-r--r--Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml180
1 files changed, 180 insertions, 0 deletions
diff --git a/Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml b/Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml
new file mode 100644
index 000000000000..f367c570c530
--- /dev/null
+++ b/Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml
@@ -0,0 +1,180 @@
+<refentry id="vidioc-subdev-g-fmt">
+ <refmeta>
+ <refentrytitle>ioctl VIDIOC_SUBDEV_G_FMT, VIDIOC_SUBDEV_S_FMT</refentrytitle>
+ &manvol;
+ </refmeta>
+
+ <refnamediv>
+ <refname>VIDIOC_SUBDEV_G_FMT</refname>
+ <refname>VIDIOC_SUBDEV_S_FMT</refname>
+ <refpurpose>Get or set the data format on a subdev pad</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_subdev_format *<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_SUBDEV_G_FMT, VIDIOC_SUBDEV_S_FMT</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>argp</parameter></term>
+ <listitem>
+ <para></para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Description</title>
+
+ <note>
+ <title>Experimental</title>
+ <para>This is an <link linkend="experimental">experimental</link>
+ interface and may change in the future.</para>
+ </note>
+
+ <para>These ioctls are used to negotiate the frame format at specific
+ subdev pads in the image pipeline.</para>
+
+ <para>To retrieve the current format applications set the
+ <structfield>pad</structfield> field of a &v4l2-subdev-format; to the
+ desired pad number as reported by the media API and the
+ <structfield>which</structfield> field to
+ <constant>V4L2_SUBDEV_FORMAT_ACTIVE</constant>. When they call the
+ <constant>VIDIOC_SUBDEV_G_FMT</constant> ioctl with a pointer to this
+ structure the driver fills the members of the <structfield>format</structfield>
+ field.</para>
+
+ <para>To change the current format applications set both the
+ <structfield>pad</structfield> and <structfield>which</structfield> fields
+ and all members of the <structfield>format</structfield> field. When they
+ call the <constant>VIDIOC_SUBDEV_S_FMT</constant> ioctl with a pointer to this
+ structure the driver verifies the requested format, adjusts it based on the
+ hardware capabilities and configures the device. Upon return the
+ &v4l2-subdev-format; contains the current format as would be returned by a
+ <constant>VIDIOC_SUBDEV_G_FMT</constant> call.</para>
+
+ <para>Applications can query the device capabilities by setting the
+ <structfield>which</structfield> to
+ <constant>V4L2_SUBDEV_FORMAT_TRY</constant>. When set, 'try' formats are not
+ applied to the device by the driver, but are changed exactly as active
+ formats and stored in the sub-device file handle. Two applications querying
+ the same sub-device would thus not interact with each other.</para>
+
+ <para>For instance, to try a format at the output pad of a sub-device,
+ applications would first set the try format at the sub-device input with the
+ <constant>VIDIOC_SUBDEV_S_FMT</constant> ioctl. They would then either
+ retrieve the default format at the output pad with the
+ <constant>VIDIOC_SUBDEV_G_FMT</constant> ioctl, or set the desired output
+ pad format with the <constant>VIDIOC_SUBDEV_S_FMT</constant> ioctl and check
+ the returned value.</para>
+
+ <para>Try formats do not depend on active formats, but can depend on the
+ current links configuration or sub-device controls value. For instance, a
+ low-pass noise filter might crop pixels at the frame boundaries, modifying
+ its output frame size.</para>
+
+ <para>Drivers must not return an error solely because the requested format
+ doesn't match the device capabilities. They must instead modify the format
+ to match what the hardware can provide. The modified format should be as
+ close as possible to the original request.</para>
+
+ <table pgwide="1" frame="none" id="v4l2-subdev-format">
+ <title>struct <structname>v4l2_subdev_format</structname></title>
+ <tgroup cols="3">
+ &cs-str;
+ <tbody valign="top">
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>pad</structfield></entry>
+ <entry>Pad number as reported by the media controller API.</entry>
+ </row>
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>which</structfield></entry>
+ <entry>Format to modified, from &v4l2-subdev-format-whence;.</entry>
+ </row>
+ <row>
+ <entry>&v4l2-mbus-framefmt;</entry>
+ <entry><structfield>format</structfield></entry>
+ <entry>Definition of an image format, see <xref
+ linkend="v4l2-mbus-framefmt" /> for details.</entry>
+ </row>
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>reserved</structfield>[8]</entry>
+ <entry>Reserved for future extensions. Applications and drivers must
+ set the array to zero.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <table pgwide="1" frame="none" id="v4l2-subdev-format-whence">
+ <title>enum <structname>v4l2_subdev_format_whence</structname></title>
+ <tgroup cols="3">
+ &cs-def;
+ <tbody valign="top">
+ <row>
+ <entry>V4L2_SUBDEV_FORMAT_TRY</entry>
+ <entry>0</entry>
+ <entry>Try formats, used for querying device capabilities.</entry>
+ </row>
+ <row>
+ <entry>V4L2_SUBDEV_FORMAT_ACTIVE</entry>
+ <entry>1</entry>
+ <entry>Active formats, applied to the hardware.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </refsect1>
+
+ <refsect1>
+ &return-value;
+
+ <variablelist>
+ <varlistentry>
+ <term><errorcode>EBUSY</errorcode></term>
+ <listitem>
+ <para>The format can't be changed because the pad is currently busy.
+ This can be caused, for instance, by an active video stream on the
+ pad. The ioctl must not be retried without performing another action
+ to fix the problem first. Only returned by
+ <constant>VIDIOC_SUBDEV_S_FMT</constant></para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorcode>EINVAL</errorcode></term>
+ <listitem>
+ <para>The &v4l2-subdev-format; <structfield>pad</structfield>
+ references a non-existing pad, or the <structfield>which</structfield>
+ field references a non-existing format.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+</refentry>