<?xml version="1.0" encoding="ANSI_X3.4-1968" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, VIDIOC_TRY_EXT_CTRLS</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="LINUX MEDIA INFRASTRUCTURE API" /><link rel="up" href="apa.html" title="Appendix A. Function Reference" /><link rel="prev" href="re38.html" title="ioctl VIDIOC_G_ENC_INDEX" /><link rel="next" href="re40.html" title="ioctl VIDIOC_G_FBUF, VIDIOC_S_FBUF" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, VIDIOC_TRY_EXT_CTRLS</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re38.html">Prev</a> </td><th width="60%" align="center">Appendix A. Function Reference</th><td width="20%" align="right"> <a accesskey="n" href="re40.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, VIDIOC_TRY_EXT_CTRLS"><a id="vidioc-g-ext-ctrls"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, VIDIOC_TRY_EXT_CTRLS — Get or set the value of several controls, try control values</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">ioctl</b>(</code></td><td>int <var class="pdparam">fd</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">request</var>, </td></tr><tr><td> </td><td>struct v4l2_ext_controls *<var class="pdparam">argp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2708058"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>fd</code></em></span></dt><dd><p>File descriptor returned by <a class="link" href="re64.html" title="V4L2 open()"><code class="function">open()</code></a>.</p></dd><dt><span class="term"><em class="parameter"><code>request</code></em></span></dt><dd><p>VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, VIDIOC_TRY_EXT_CTRLS</p></dd><dt><span class="term"><em class="parameter"><code>argp</code></em></span></dt><dd><p></p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2708127"></a><h2>Description</h2><p>These ioctls allow the caller to get or set multiple controls atomically. Control IDs are grouped into control classes (see <a class="xref" href="re39.html#ctrl-class" title="Table A.42. Control classes">Table A.42, “Control classes”</a>) and all controls in the control array must belong to the same control class.</p><p>Applications must always fill in the <em class="structfield"><code>count</code></em>, <em class="structfield"><code>ctrl_class</code></em>, <em class="structfield"><code>controls</code></em> and <em class="structfield"><code>reserved</code></em> fields of struct <a class="link" href="re39.html#v4l2-ext-controls" title="Table A.41. struct v4l2_ext_controls">v4l2_ext_controls</a>, and initialize the struct <a class="link" href="re39.html#v4l2-ext-control" title="Table A.40. struct v4l2_ext_control">v4l2_ext_control</a> array pointed to by the <em class="structfield"><code>controls</code></em> fields.</p><p>To get the current value of a set of controls applications initialize the <em class="structfield"><code>id</code></em>, <em class="structfield"><code>size</code></em> and <em class="structfield"><code>reserved2</code></em> fields of each struct <a class="link" href="re39.html#v4l2-ext-control" title="Table A.40. struct v4l2_ext_control">v4l2_ext_control</a> and call the <code class="constant">VIDIOC_G_EXT_CTRLS</code> ioctl. String controls controls must also set the <em class="structfield"><code>string</code></em> field.</p><p>If the <em class="structfield"><code>size</code></em> is too small to receive the control result (only relevant for pointer-type controls like strings), then the driver will set <em class="structfield"><code>size</code></em> to a valid value and return an <span class="errorcode">ENOSPC</span> error code. You should re-allocate the string memory to this new size and try again. It is possible that the same issue occurs again if the string has grown in the meantime. It is recommended to call <a class="link" href="re57.html" title="ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU"><code class="constant">VIDIOC_QUERYCTRL</code></a> first and use <em class="structfield"><code>maximum</code></em>+1 as the new <em class="structfield"><code>size</code></em> value. It is guaranteed that that is sufficient memory. </p><p>To change the value of a set of controls applications initialize the <em class="structfield"><code>id</code></em>, <em class="structfield"><code>size</code></em>, <em class="structfield"><code>reserved2</code></em> and <em class="structfield"><code>value/string</code></em> fields of each struct <a class="link" href="re39.html#v4l2-ext-control" title="Table A.40. struct v4l2_ext_control">v4l2_ext_control</a> and call the <code class="constant">VIDIOC_S_EXT_CTRLS</code> ioctl. The controls will only be set if <span class="emphasis"><em>all</em></span> control values are valid.</p><p>To check if a set of controls have correct values applications initialize the <em class="structfield"><code>id</code></em>, <em class="structfield"><code>size</code></em>, <em class="structfield"><code>reserved2</code></em> and <em class="structfield"><code>value/string</code></em> fields of each struct <a class="link" href="re39.html#v4l2-ext-control" title="Table A.40. struct v4l2_ext_control">v4l2_ext_control</a> and call the <code class="constant">VIDIOC_TRY_EXT_CTRLS</code> ioctl. It is up to the driver whether wrong values are automatically adjusted to a valid value or if an error is returned.</p><p>When the <em class="structfield"><code>id</code></em> or <em class="structfield"><code>ctrl_class</code></em> is invalid drivers return an <span class="errorcode">EINVAL</span> error code. When the value is out of bounds drivers can choose to take the closest valid value or return an <span class="errorcode">ERANGE</span> error code, whatever seems more appropriate. In the first case the new value is set in struct <a class="link" href="re39.html#v4l2-ext-control" title="Table A.40. struct v4l2_ext_control">v4l2_ext_control</a>.</p><p>The driver will only set/get these controls if all control values are correct. This prevents the situation where only some of the controls were set/get. Only low-level errors (e. g. a failed i2c command) can still cause this situation.</p><div class="table"><a id="v4l2-ext-control"></a><p class="title"><b>Table A.40. struct <span class="structname">v4l2_ext_control</span></b></p><div class="table-contents"><table summary="struct v4l2_ext_control" width="100%" border="0"><colgroup><col /><col /><col /><col /></colgroup><tbody valign="top"><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>id</code></em></td><td valign="top"> </td><td valign="top">Identifies the control, set by the application.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>size</code></em></td><td valign="top"> </td><td valign="top">The total size in bytes of the payload of this control. This is normally 0, but for pointer controls this should be set to the size of the memory containing the payload, or that will receive the payload. If <code class="constant">VIDIOC_G_EXT_CTRLS</code> finds that this value is less than is required to store the payload result, then it is set to a value large enough to store the payload result and ENOSPC is returned. Note that for string controls this <em class="structfield"><code>size</code></em> field should not be confused with the length of the string. This field refers to the size of the memory that contains the string. The actual <span class="emphasis"><em>length</em></span> of the string may well be much smaller. </td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>reserved2</code></em>[1]</td><td valign="top"> </td><td valign="top">Reserved for future extensions. Drivers and applications must set the array to zero.</td></tr><tr><td valign="top">union</td><td valign="top">(anonymous)</td><td class="auto-generated"> </td><td class="auto-generated"> </td></tr><tr><td valign="top"> </td><td valign="top">__s32</td><td valign="top"><em class="structfield"><code>value</code></em></td><td valign="top">New value or current value.</td></tr><tr><td valign="top"> </td><td valign="top">__s64</td><td valign="top"><em class="structfield"><code>value64</code></em></td><td valign="top">New value or current value.</td></tr><tr><td valign="top"> </td><td valign="top">char *</td><td valign="top"><em class="structfield"><code>string</code></em></td><td valign="top">A pointer to a string.</td></tr></tbody></table></div></div><br class="table-break" /><div class="table"><a id="v4l2-ext-controls"></a><p class="title"><b>Table A.41. struct <span class="structname">v4l2_ext_controls</span></b></p><div class="table-contents"><table summary="struct v4l2_ext_controls" width="100%" border="0"><colgroup><col /><col /><col /></colgroup><tbody valign="top"><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>ctrl_class</code></em></td><td valign="top">The control class to which all controls belong, see <a class="xref" href="re39.html#ctrl-class" title="Table A.42. Control classes">Table A.42, “Control classes”</a>.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>count</code></em></td><td valign="top">The number of controls in the controls array. May also be zero.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>error_idx</code></em></td><td valign="top">Set by the driver in case of an error. It is the index of the control causing the error or equal to 'count' when the error is not associated with a particular control. Undefined when the ioctl returns 0 (success).</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>reserved</code></em>[2]</td><td valign="top">Reserved for future extensions. Drivers and applications must set the array to zero.</td></tr><tr><td valign="top">struct <a class="link" href="re39.html#v4l2-ext-control" title="Table A.40. struct v4l2_ext_control">v4l2_ext_control</a> *</td><td valign="top"><em class="structfield"><code>controls</code></em></td><td valign="top">Pointer to an array of <em class="structfield"><code>count</code></em> v4l2_ext_control structures. Ignored if <em class="structfield"><code>count</code></em> equals zero.</td></tr></tbody></table></div></div><br class="table-break" /><div class="table"><a id="ctrl-class"></a><p class="title"><b>Table A.42. Control classes</b></p><div class="table-contents"><table summary="Control classes" width="100%" border="0"><colgroup><col /><col /><col /></colgroup><tbody valign="top"><tr><td valign="top"><code class="constant">V4L2_CTRL_CLASS_USER</code></td><td valign="top">0x980000</td><td valign="top">The class containing user controls. These controls are described in <a class="xref" href="ch01s08.html" title="User Controls">the section called “User Controls”</a>. All controls that can be set using the <a class="link" href="re37.html" title="ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL"><code class="constant">VIDIOC_S_CTRL</code></a> and <a class="link" href="re37.html" title="ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL"><code class="constant">VIDIOC_G_CTRL</code></a> ioctl belong to this class.</td></tr><tr><td valign="top"><code class="constant">V4L2_CTRL_CLASS_MPEG</code></td><td valign="top">0x990000</td><td valign="top">The class containing MPEG compression controls. These controls are described in <a class="xref" href="ch01s09.html#mpeg-controls" title="MPEG Control Reference">the section called “MPEG Control Reference”</a>.</td></tr><tr><td valign="top"><code class="constant">V4L2_CTRL_CLASS_CAMERA</code></td><td valign="top">0x9a0000</td><td valign="top">The class containing camera controls. These controls are described in <a class="xref" href="ch01s09.html#camera-controls" title="Camera Control Reference">the section called “Camera Control Reference”</a>.</td></tr><tr><td valign="top"><code class="constant">V4L2_CTRL_CLASS_FM_TX</code></td><td valign="top">0x9b0000</td><td valign="top">The class containing FM Transmitter (FM TX) controls. These controls are described in <a class="xref" href="ch01s09.html#fm-tx-controls" title="FM Transmitter Control Reference">the section called “FM Transmitter Control Reference”</a>.</td></tr></tbody></table></div></div><br class="table-break" /></div><div class="refsect1" title="Return Value"><a id="id2708871"></a><h2>Return Value</h2><p>On success <span class="returnvalue">0</span> is returned, on error <span class="returnvalue">-1</span> and the <code class="varname">errno</code> variable is set appropriately:</p><div class="variablelist"><dl><dt><span class="term"><span class="errorcode">EINVAL</span></span></dt><dd><p>The struct <a class="link" href="re39.html#v4l2-ext-control" title="Table A.40. struct v4l2_ext_control">v4l2_ext_control</a> <em class="structfield"><code>id</code></em> is invalid or the struct <a class="link" href="re39.html#v4l2-ext-controls" title="Table A.41. struct v4l2_ext_controls">v4l2_ext_controls</a> <em class="structfield"><code>ctrl_class</code></em> is invalid. This error code is also returned by the <code class="constant">VIDIOC_S_EXT_CTRLS</code> and <code class="constant">VIDIOC_TRY_EXT_CTRLS</code> ioctls if two or more control values are in conflict.</p></dd><dt><span class="term"><span class="errorcode">ERANGE</span></span></dt><dd><p>The struct <a class="link" href="re39.html#v4l2-ext-control" title="Table A.40. struct v4l2_ext_control">v4l2_ext_control</a> <em class="structfield"><code>value</code></em> is out of bounds.</p></dd><dt><span class="term"><span class="errorcode">EBUSY</span></span></dt><dd><p>The control is temporarily not changeable, possibly because another applications took over control of the device function this control belongs to.</p></dd><dt><span class="term"><span class="errorcode">ENOSPC</span></span></dt><dd><p>The space reserved for the control's payload is insufficient. The field <em class="structfield"><code>size</code></em> is set to a value that is enough to store the payload and this error code is returned.</p></dd></dl></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re38.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="apa.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re40.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">ioctl VIDIOC_G_ENC_INDEX </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> ioctl VIDIOC_G_FBUF, VIDIOC_S_FBUF</td></tr></table></div></body></html>
