429 lines
16 KiB
XML
429 lines
16 KiB
XML
|
<refentry id="vidioc-queryctrl">
|
||
|
|
<refmeta>
|
||
|
|
<refentrytitle>ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU</refentrytitle>
|
||
|
|
&manvol;
|
||
|
|
</refmeta>
|
||
|
|
|
||
|
|
<refnamediv>
|
||
|
|
<refname>VIDIOC_QUERYCTRL</refname>
|
||
|
|
<refname>VIDIOC_QUERYMENU</refname>
|
||
|
|
<refpurpose>Enumerate controls and menu control items</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_queryctrl *<parameter>argp</parameter></paramdef>
|
||
|
|
</funcprototype>
|
||
|
|
</funcsynopsis>
|
||
|
|
<funcsynopsis>
|
||
|
|
<funcprototype>
|
||
|
|
<funcdef>int <function>ioctl</function></funcdef>
|
||
|
|
<paramdef>int <parameter>fd</parameter></paramdef>
|
||
|
|
<paramdef>int <parameter>request</parameter></paramdef>
|
||
|
|
<paramdef>struct v4l2_querymenu *<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_QUERYCTRL, VIDIOC_QUERYMENU</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><parameter>argp</parameter></term>
|
||
|
|
<listitem>
|
||
|
|
<para></para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
</variablelist>
|
||
|
|
</refsect1>
|
||
|
|
|
||
|
|
<refsect1>
|
||
|
|
<title>Description</title>
|
||
|
|
|
||
|
|
<para>To query the attributes of a control applications set the
|
||
|
|
<structfield>id</structfield> field of a &v4l2-queryctrl; and call the
|
||
|
|
<constant>VIDIOC_QUERYCTRL</constant> ioctl with a pointer to this
|
||
|
|
structure. The driver fills the rest of the structure or returns an
|
||
|
|
&EINVAL; when the <structfield>id</structfield> is invalid.</para>
|
||
|
|
|
||
|
|
<para>It is possible to enumerate controls by calling
|
||
|
|
<constant>VIDIOC_QUERYCTRL</constant> with successive
|
||
|
|
<structfield>id</structfield> values starting from
|
||
|
|
<constant>V4L2_CID_BASE</constant> up to and exclusive
|
||
|
|
<constant>V4L2_CID_BASE_LASTP1</constant>. Drivers may return
|
||
|
|
<errorcode>EINVAL</errorcode> if a control in this range is not
|
||
|
|
supported. Further applications can enumerate private controls, which
|
||
|
|
are not defined in this specification, by starting at
|
||
|
|
<constant>V4L2_CID_PRIVATE_BASE</constant> and incrementing
|
||
|
|
<structfield>id</structfield> until the driver returns
|
||
|
|
<errorcode>EINVAL</errorcode>.</para>
|
||
|
|
|
||
|
|
<para>In both cases, when the driver sets the
|
||
|
|
<constant>V4L2_CTRL_FLAG_DISABLED</constant> flag in the
|
||
|
|
<structfield>flags</structfield> field this control is permanently
|
||
|
|
disabled and should be ignored by the application.<footnote>
|
||
|
|
<para><constant>V4L2_CTRL_FLAG_DISABLED</constant> was
|
||
|
|
intended for two purposes: Drivers can skip predefined controls not
|
||
|
|
supported by the hardware (although returning EINVAL would do as
|
||
|
|
well), or disable predefined and private controls after hardware
|
||
|
|
detection without the trouble of reordering control arrays and indices
|
||
|
|
(EINVAL cannot be used to skip private controls because it would
|
||
|
|
prematurely end the enumeration).</para></footnote></para>
|
||
|
|
|
||
|
|
<para>When the application ORs <structfield>id</structfield> with
|
||
|
|
<constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> the driver returns the
|
||
|
|
next supported control, or <errorcode>EINVAL</errorcode> if there is
|
||
|
|
none. Drivers which do not support this flag yet always return
|
||
|
|
<errorcode>EINVAL</errorcode>.</para>
|
||
|
|
|
||
|
|
<para>Additional information is required for menu controls: the
|
||
|
|
names of the menu items. To query them applications set the
|
||
|
|
<structfield>id</structfield> and <structfield>index</structfield>
|
||
|
|
fields of &v4l2-querymenu; and call the
|
||
|
|
<constant>VIDIOC_QUERYMENU</constant> ioctl with a pointer to this
|
||
|
|
structure. The driver fills the rest of the structure or returns an
|
||
|
|
&EINVAL; when the <structfield>id</structfield> or
|
||
|
|
<structfield>index</structfield> is invalid. Menu items are enumerated
|
||
|
|
by calling <constant>VIDIOC_QUERYMENU</constant> with successive
|
||
|
|
<structfield>index</structfield> values from &v4l2-queryctrl;
|
||
|
|
<structfield>minimum</structfield> (0) to
|
||
|
|
<structfield>maximum</structfield>, inclusive.</para>
|
||
|
|
|
||
|
|
<para>See also the examples in <xref linkend="control" />.</para>
|
||
|
|
|
||
|
|
<table pgwide="1" frame="none" id="v4l2-queryctrl">
|
||
|
|
<title>struct <structname>v4l2_queryctrl</structname></title>
|
||
|
|
<tgroup cols="3">
|
||
|
|
&cs-str;
|
||
|
|
<tbody valign="top">
|
||
|
|
<row>
|
||
|
|
<entry>__u32</entry>
|
||
|
|
<entry><structfield>id</structfield></entry>
|
||
|
|
<entry>Identifies the control, set by the application. See
|
||
|
|
<xref linkend="control-id" /> for predefined IDs. When the ID is ORed
|
||
|
|
with V4L2_CTRL_FLAG_NEXT_CTRL the driver clears the flag and returns
|
||
|
|
the first control with a higher ID. Drivers which do not support this
|
||
|
|
flag yet always return an &EINVAL;.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry>&v4l2-ctrl-type;</entry>
|
||
|
|
<entry><structfield>type</structfield></entry>
|
||
|
|
<entry>Type of control, see <xref
|
||
|
|
linkend="v4l2-ctrl-type" />.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry>__u8</entry>
|
||
|
|
<entry><structfield>name</structfield>[32]</entry>
|
||
|
|
<entry>Name of the control, a NUL-terminated ASCII
|
||
|
|
string. This information is intended for the user.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry>__s32</entry>
|
||
|
|
<entry><structfield>minimum</structfield></entry>
|
||
|
|
<entry>Minimum value, inclusive. This field gives a lower
|
||
|
|
bound for <constant>V4L2_CTRL_TYPE_INTEGER</constant> controls and the
|
||
|
|
lowest valid index (always 0) for <constant>V4L2_CTRL_TYPE_MENU</constant> controls.
|
||
|
|
For <constant>V4L2_CTRL_TYPE_STRING</constant> controls the minimum value
|
||
|
|
gives the minimum length of the string. This length <emphasis>does not include the terminating
|
||
|
|
zero</emphasis>. It may not be valid for any other type of control, including
|
||
|
|
<constant>V4L2_CTRL_TYPE_INTEGER64</constant> controls. Note that this is a
|
||
|
|
signed value.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry>__s32</entry>
|
||
|
|
<entry><structfield>maximum</structfield></entry>
|
||
|
|
<entry>Maximum value, inclusive. This field gives an upper
|
||
|
|
bound for <constant>V4L2_CTRL_TYPE_INTEGER</constant> controls and the
|
||
|
|
highest valid index for <constant>V4L2_CTRL_TYPE_MENU</constant>
|
||
|
|
controls.
|
||
|
|
For <constant>V4L2_CTRL_TYPE_STRING</constant> controls the maximum value
|
||
|
|
gives the maximum length of the string. This length <emphasis>does not include the terminating
|
||
|
|
zero</emphasis>. It may not be valid for any other type of control, including
|
||
|
|
<constant>V4L2_CTRL_TYPE_INTEGER64</constant> controls. Note that this is a
|
||
|
|
signed value.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry>__s32</entry>
|
||
|
|
<entry><structfield>step</structfield></entry>
|
||
|
|
<entry><para>This field gives a step size for
|
||
|
|
<constant>V4L2_CTRL_TYPE_INTEGER</constant> controls. For
|
||
|
|
<constant>V4L2_CTRL_TYPE_STRING</constant> controls this field refers to
|
||
|
|
the string length that has to be a multiple of this step size.
|
||
|
|
It may not be valid for any other type of control, including
|
||
|
|
<constant>V4L2_CTRL_TYPE_INTEGER64</constant>
|
||
|
|
controls.</para><para>Generally drivers should not scale hardware
|
||
|
|
control values. It may be necessary for example when the
|
||
|
|
<structfield>name</structfield> or <structfield>id</structfield> imply
|
||
|
|
a particular unit and the hardware actually accepts only multiples of
|
||
|
|
said unit. If so, drivers must take care values are properly rounded
|
||
|
|
when scaling, such that errors will not accumulate on repeated
|
||
|
|
read-write cycles.</para><para>This field gives the smallest change of
|
||
|
|
an integer control actually affecting hardware. Often the information
|
||
|
|
is needed when the user can change controls by keyboard or GUI
|
||
|
|
buttons, rather than a slider. When for example a hardware register
|
||
|
|
accepts values 0-511 and the driver reports 0-65535, step should be
|
||
|
|
128.</para><para>Note that although signed, the step value is supposed to
|
||
|
|
be always positive.</para></entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry>__s32</entry>
|
||
|
|
<entry><structfield>default_value</structfield></entry>
|
||
|
|
<entry>The default value of a
|
||
|
|
<constant>V4L2_CTRL_TYPE_INTEGER</constant>,
|
||
|
|
<constant>_BOOLEAN</constant> or <constant>_MENU</constant> control.
|
||
|
|
Not valid for other types of controls. Drivers reset controls only
|
||
|
|
when the driver is loaded, not later, in particular not when the
|
||
|
|
func-open; is called.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry>__u32</entry>
|
||
|
|
<entry><structfield>flags</structfield></entry>
|
||
|
|
<entry>Control flags, see <xref
|
||
|
|
linkend="control-flags" />.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry>__u32</entry>
|
||
|
|
<entry><structfield>reserved</structfield>[2]</entry>
|
||
|
|
<entry>Reserved for future extensions. Drivers must set
|
||
|
|
the array to zero.</entry>
|
||
|
|
</row>
|
||
|
|
</tbody>
|
||
|
|
</tgroup>
|
||
|
|
</table>
|
||
|
|
|
||
|
|
<table pgwide="1" frame="none" id="v4l2-querymenu">
|
||
|
|
<title>struct <structname>v4l2_querymenu</structname></title>
|
||
|
|
<tgroup cols="3">
|
||
|
|
&cs-str;
|
||
|
|
<tbody valign="top">
|
||
|
|
<row>
|
||
|
|
<entry>__u32</entry>
|
||
|
|
<entry><structfield>id</structfield></entry>
|
||
|
|
<entry>Identifies the control, set by the application
|
||
|
|
from the respective &v4l2-queryctrl;
|
||
|
|
<structfield>id</structfield>.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry>__u32</entry>
|
||
|
|
<entry><structfield>index</structfield></entry>
|
||
|
|
<entry>Index of the menu item, starting at zero, set by
|
||
|
|
the application.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry>__u8</entry>
|
||
|
|
<entry><structfield>name</structfield>[32]</entry>
|
||
|
|
<entry>Name of the menu item, a NUL-terminated ASCII
|
||
|
|
string. This information is intended for the user.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry>__u32</entry>
|
||
|
|
<entry><structfield>reserved</structfield></entry>
|
||
|
|
<entry>Reserved for future extensions. Drivers must set
|
||
|
|
the array to zero.</entry>
|
||
|
|
</row>
|
||
|
|
</tbody>
|
||
|
|
</tgroup>
|
||
|
|
</table>
|
||
|
|
|
||
|
|
<table pgwide="1" frame="none" id="v4l2-ctrl-type">
|
||
|
|
<title>enum v4l2_ctrl_type</title>
|
||
|
|
<tgroup cols="5" align="left">
|
||
|
|
<colspec colwidth="30*" />
|
||
|
|
<colspec colwidth="5*" align="center" />
|
||
|
|
<colspec colwidth="5*" align="center" />
|
||
|
|
<colspec colwidth="5*" align="center" />
|
||
|
|
<colspec colwidth="55*" />
|
||
|
|
<thead>
|
||
|
|
<row>
|
||
|
|
<entry>Type</entry>
|
||
|
|
<entry><structfield>minimum</structfield></entry>
|
||
|
|
<entry><structfield>step</structfield></entry>
|
||
|
|
<entry><structfield>maximum</structfield></entry>
|
||
|
|
<entry>Description</entry>
|
||
|
|
</row>
|
||
|
|
</thead>
|
||
|
|
<tbody valign="top">
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_TYPE_INTEGER</constant></entry>
|
||
|
|
<entry>any</entry>
|
||
|
|
<entry>any</entry>
|
||
|
|
<entry>any</entry>
|
||
|
|
<entry>An integer-valued control ranging from minimum to
|
||
|
|
maximum inclusive. The step value indicates the increment between
|
||
|
|
values which are actually different on the hardware.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_TYPE_BOOLEAN</constant></entry>
|
||
|
|
<entry>0</entry>
|
||
|
|
<entry>1</entry>
|
||
|
|
<entry>1</entry>
|
||
|
|
<entry>A boolean-valued control. Zero corresponds to
|
||
|
|
"disabled", and one means "enabled".</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_TYPE_MENU</constant></entry>
|
||
|
|
<entry>0</entry>
|
||
|
|
<entry>1</entry>
|
||
|
|
<entry>N-1</entry>
|
||
|
|
<entry>The control has a menu of N choices. The names of
|
||
|
|
the menu items can be enumerated with the
|
||
|
|
<constant>VIDIOC_QUERYMENU</constant> ioctl.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_TYPE_BUTTON</constant></entry>
|
||
|
|
<entry>0</entry>
|
||
|
|
<entry>0</entry>
|
||
|
|
<entry>0</entry>
|
||
|
|
<entry>A control which performs an action when set.
|
||
|
|
Drivers must ignore the value passed with
|
||
|
|
<constant>VIDIOC_S_CTRL</constant> and return an &EINVAL; on a
|
||
|
|
<constant>VIDIOC_G_CTRL</constant> attempt.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_TYPE_INTEGER64</constant></entry>
|
||
|
|
<entry>n/a</entry>
|
||
|
|
<entry>n/a</entry>
|
||
|
|
<entry>n/a</entry>
|
||
|
|
<entry>A 64-bit integer valued control. Minimum, maximum
|
||
|
|
and step size cannot be queried.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_TYPE_STRING</constant></entry>
|
||
|
|
<entry>≥ 0</entry>
|
||
|
|
<entry>≥ 1</entry>
|
||
|
|
<entry>≥ 0</entry>
|
||
|
|
<entry>The minimum and maximum string lengths. The step size
|
||
|
|
means that the string must be (minimum + N * step) characters long for
|
||
|
|
N ≥ 0. These lengths do not include the terminating zero, so in order to
|
||
|
|
pass a string of length 8 to &VIDIOC-S-EXT-CTRLS; you need to set the
|
||
|
|
<structfield>size</structfield> field of &v4l2-ext-control; to 9. For &VIDIOC-G-EXT-CTRLS; you can
|
||
|
|
set the <structfield>size</structfield> field to <structfield>maximum</structfield> + 1.
|
||
|
|
Which character encoding is used will depend on the string control itself and
|
||
|
|
should be part of the control documentation.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_TYPE_CTRL_CLASS</constant></entry>
|
||
|
|
<entry>n/a</entry>
|
||
|
|
<entry>n/a</entry>
|
||
|
|
<entry>n/a</entry>
|
||
|
|
<entry>This is not a control. When
|
||
|
|
<constant>VIDIOC_QUERYCTRL</constant> is called with a control ID
|
||
|
|
equal to a control class code (see <xref linkend="ctrl-class" />), the
|
||
|
|
ioctl returns the name of the control class and this control type.
|
||
|
|
Older drivers which do not support this feature return an
|
||
|
|
&EINVAL;.</entry>
|
||
|
|
</row>
|
||
|
|
</tbody>
|
||
|
|
</tgroup>
|
||
|
|
</table>
|
||
|
|
|
||
|
|
<table pgwide="1" frame="none" id="control-flags">
|
||
|
|
<title>Control Flags</title>
|
||
|
|
<tgroup cols="3">
|
||
|
|
&cs-def;
|
||
|
|
<tbody valign="top">
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_FLAG_DISABLED</constant></entry>
|
||
|
|
<entry>0x0001</entry>
|
||
|
|
<entry>This control is permanently disabled and should be
|
||
|
|
ignored by the application. Any attempt to change the control will
|
||
|
|
result in an &EINVAL;.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_FLAG_GRABBED</constant></entry>
|
||
|
|
<entry>0x0002</entry>
|
||
|
|
<entry>This control is temporarily unchangeable, for
|
||
|
|
example because another application took over control of the
|
||
|
|
respective resource. Such controls may be displayed specially in a
|
||
|
|
user interface. Attempts to change the control may result in an
|
||
|
|
&EBUSY;.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_FLAG_READ_ONLY</constant></entry>
|
||
|
|
<entry>0x0004</entry>
|
||
|
|
<entry>This control is permanently readable only. Any
|
||
|
|
attempt to change the control will result in an &EINVAL;.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_FLAG_UPDATE</constant></entry>
|
||
|
|
<entry>0x0008</entry>
|
||
|
|
<entry>A hint that changing this control may affect the
|
||
|
|
value of other controls within the same control class. Applications
|
||
|
|
should update their user interface accordingly.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_FLAG_INACTIVE</constant></entry>
|
||
|
|
<entry>0x0010</entry>
|
||
|
|
<entry>This control is not applicable to the current
|
||
|
|
configuration and should be displayed accordingly in a user interface.
|
||
|
|
For example the flag may be set on a MPEG audio level 2 bitrate
|
||
|
|
control when MPEG audio encoding level 1 was selected with another
|
||
|
|
control.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_FLAG_SLIDER</constant></entry>
|
||
|
|
<entry>0x0020</entry>
|
||
|
|
<entry>A hint that this control is best represented as a
|
||
|
|
slider-like element in a user interface.</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry><constant>V4L2_CTRL_FLAG_WRITE_ONLY</constant></entry>
|
||
|
|
<entry>0x0040</entry>
|
||
|
|
<entry>This control is permanently writable only. Any
|
||
|
|
attempt to read the control will result in an &EACCES; error code. This
|
||
|
|
flag is typically present for relative controls or action controls where
|
||
|
|
writing a value will cause the device to carry out a given action
|
||
|
|
(⪚ motor control) but no meaningful value can be returned.</entry>
|
||
|
|
</row>
|
||
|
|
</tbody>
|
||
|
|
</tgroup>
|
||
|
|
</table>
|
||
|
|
</refsect1>
|
||
|
|
|
||
|
|
<refsect1>
|
||
|
|
&return-value;
|
||
|
|
|
||
|
|
<variablelist>
|
||
|
|
<varlistentry>
|
||
|
|
<term><errorcode>EINVAL</errorcode></term>
|
||
|
|
<listitem>
|
||
|
|
<para>The &v4l2-queryctrl; <structfield>id</structfield>
|
||
|
|
is invalid. The &v4l2-querymenu; <structfield>id</structfield> or
|
||
|
|
<structfield>index</structfield> is invalid.</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><errorcode>EACCES</errorcode></term>
|
||
|
|
<listitem>
|
||
|
|
<para>An attempt was made to read a write-only control.</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
</variablelist>
|
||
|
|
</refsect1>
|
||
|
|
</refentry>
|
||
|
|
|
||
|
|
<!--
|
||
|
|
Local Variables:
|
||
|
|
mode: sgml
|
||
|
|
sgml-parent-document: "v4l2.sgml"
|
||
|
|
indent-tabs-mode: nil
|
||
|
|
End:
|
||
|
|
-->
|