1<refentry id="vidioc-subdev-g-crop">
2  <refmeta>
3    <refentrytitle>ioctl VIDIOC_SUBDEV_G_CROP, VIDIOC_SUBDEV_S_CROP</refentrytitle>
4    &manvol;
5  </refmeta>
6
7  <refnamediv>
8    <refname>VIDIOC_SUBDEV_G_CROP</refname>
9    <refname>VIDIOC_SUBDEV_S_CROP</refname>
10    <refpurpose>Get or set the crop rectangle on a subdev pad</refpurpose>
11  </refnamediv>
12
13  <refsynopsisdiv>
14    <funcsynopsis>
15      <funcprototype>
16	<funcdef>int <function>ioctl</function></funcdef>
17	<paramdef>int <parameter>fd</parameter></paramdef>
18	<paramdef>int <parameter>request</parameter></paramdef>
19	<paramdef>struct v4l2_subdev_crop *<parameter>argp</parameter></paramdef>
20      </funcprototype>
21    </funcsynopsis>
22    <funcsynopsis>
23      <funcprototype>
24	<funcdef>int <function>ioctl</function></funcdef>
25	<paramdef>int <parameter>fd</parameter></paramdef>
26	<paramdef>int <parameter>request</parameter></paramdef>
27	<paramdef>const struct v4l2_subdev_crop *<parameter>argp</parameter></paramdef>
28      </funcprototype>
29    </funcsynopsis>
30  </refsynopsisdiv>
31
32  <refsect1>
33    <title>Arguments</title>
34
35    <variablelist>
36      <varlistentry>
37	<term><parameter>fd</parameter></term>
38	<listitem>
39	  <para>&fd;</para>
40	</listitem>
41      </varlistentry>
42      <varlistentry>
43	<term><parameter>request</parameter></term>
44	<listitem>
45	  <para>VIDIOC_SUBDEV_G_CROP, VIDIOC_SUBDEV_S_CROP</para>
46	</listitem>
47      </varlistentry>
48      <varlistentry>
49	<term><parameter>argp</parameter></term>
50	<listitem>
51	  <para></para>
52	</listitem>
53      </varlistentry>
54    </variablelist>
55  </refsect1>
56
57  <refsect1>
58    <title>Description</title>
59
60    <note>
61      <title>Experimental</title>
62      <para>This is an <link linkend="experimental">experimental</link>
63      interface and may change in the future.</para>
64    </note>
65
66    <para>To retrieve the current crop rectangle applications set the
67    <structfield>pad</structfield> field of a &v4l2-subdev-crop; to the
68    desired pad number as reported by the media API and the
69    <structfield>which</structfield> field to
70    <constant>V4L2_SUBDEV_FORMAT_ACTIVE</constant>. They then call the
71    <constant>VIDIOC_SUBDEV_G_CROP</constant> ioctl with a pointer to this
72    structure. The driver fills the members of the <structfield>rect</structfield>
73    field or returns &EINVAL; if the input arguments are invalid, or if cropping
74    is not supported on the given pad.</para>
75
76    <para>To change the current crop rectangle applications set both the
77    <structfield>pad</structfield> and <structfield>which</structfield> fields
78    and all members of the <structfield>rect</structfield> field. They then call
79    the <constant>VIDIOC_SUBDEV_S_CROP</constant> ioctl with a pointer to this
80    structure. The driver verifies the requested crop rectangle, adjusts it
81    based on the hardware capabilities and configures the device. Upon return
82    the &v4l2-subdev-crop; contains the current format as would be returned
83    by a <constant>VIDIOC_SUBDEV_G_CROP</constant> call.</para>
84
85    <para>Applications can query the device capabilities by setting the
86    <structfield>which</structfield> to
87    <constant>V4L2_SUBDEV_FORMAT_TRY</constant>. When set, 'try' crop
88    rectangles are not applied to the device by the driver, but are mangled
89    exactly as active crop rectangles and stored in the sub-device file handle.
90    Two applications querying the same sub-device would thus not interact with
91    each other.</para>
92
93    <para>Drivers must not return an error solely because the requested crop
94    rectangle doesn't match the device capabilities. They must instead modify
95    the rectangle to match what the hardware can provide. The modified format
96    should be as close as possible to the original request.</para>
97
98    <table pgwide="1" frame="none" id="v4l2-subdev-crop">
99      <title>struct <structname>v4l2_subdev_crop</structname></title>
100      <tgroup cols="3">
101        &cs-str;
102	<tbody valign="top">
103	  <row>
104	    <entry>__u32</entry>
105	    <entry><structfield>pad</structfield></entry>
106	    <entry>Pad number as reported by the media framework.</entry>
107	  </row>
108	  <row>
109	    <entry>__u32</entry>
110	    <entry><structfield>which</structfield></entry>
111	    <entry>Crop rectangle to get or set, from
112	    &v4l2-subdev-format-whence;.</entry>
113	  </row>
114	  <row>
115	    <entry>&v4l2-rect;</entry>
116	    <entry><structfield>rect</structfield></entry>
117	    <entry>Crop rectangle boundaries, in pixels.</entry>
118	  </row>
119	  <row>
120	    <entry>__u32</entry>
121	    <entry><structfield>reserved</structfield>[8]</entry>
122	    <entry>Reserved for future extensions. Applications and drivers must
123	    set the array to zero.</entry>
124	  </row>
125	</tbody>
126      </tgroup>
127    </table>
128  </refsect1>
129
130  <refsect1>
131    &return-value;
132
133    <variablelist>
134      <varlistentry>
135	<term><errorcode>EBUSY</errorcode></term>
136	<listitem>
137	  <para>The crop rectangle can't be changed because the pad is currently
138	  busy. This can be caused, for instance, by an active video stream on
139	  the pad. The ioctl must not be retried without performing another
140	  action to fix the problem first. Only returned by
141	  <constant>VIDIOC_SUBDEV_S_CROP</constant></para>
142	</listitem>
143      </varlistentry>
144      <varlistentry>
145	<term><errorcode>EINVAL</errorcode></term>
146	<listitem>
147	  <para>The &v4l2-subdev-crop; <structfield>pad</structfield>
148	  references a non-existing pad, the <structfield>which</structfield>
149	  field references a non-existing format, or cropping is not supported
150	  on the given subdev pad.</para>
151	</listitem>
152      </varlistentry>
153    </variablelist>
154  </refsect1>
155</refentry>
156