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Commit 715bfb3e authored by Hans Verkuil's avatar Hans Verkuil Committed by Mauro Carvalho Chehab
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[media] DocBook media: document VIDIOC_QUERY_EXT_CTRL 

Document the new VIDIOC_QUERY_EXT_CTRL ioctl.
Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: default avatarMauro Carvalho Chehab <m.chehab@samsung.com>
parent 40265bbe
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Documentation/DocBook/media/v4l/vidioc-queryctrl.xml
View file @ 715bfb3e
<refentry id="vidioc-queryctrl">
<refmeta>
<refentrytitle>ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU</refentrytitle>
<refentrytitle>ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERY_EXT_CTRL, VIDIOC_QUERYMENU</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname>VIDIOC_QUERYCTRL</refname>
<refname>VIDIOC_QUERY_EXT_CTRL</refname>
<refname>VIDIOC_QUERYMENU</refname>
<refpurpose>Enumerate controls and menu control items</refpurpose>
</refnamediv>
......@@ -19,6 +20,14 @@
<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_query_ext_ctrl *<parameter>argp</parameter></paramdef>
</funcprototype>
</funcsynopsis>
<funcsynopsis>
<funcprototype>
<funcdef>int <function>ioctl</function></funcdef>
......@@ -42,7 +51,7 @@
<varlistentry>
<term><parameter>request</parameter></term>
<listitem>
<para>VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU</para>
<para>VIDIOC_QUERYCTRL, VIDIOC_QUERY_EXT_CTRL, VIDIOC_QUERYMENU</para>
</listitem>
</varlistentry>
<varlistentry>
......@@ -89,9 +98,23 @@ 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>
next supported non-compound control, or <errorcode>EINVAL</errorcode>
if there is none. In addition, the <constant>V4L2_CTRL_FLAG_NEXT_COMPOUND</constant>
flag can be specified to enumerate all compound controls (i.e. controls
with type &ge; <constant>V4L2_CTRL_COMPOUND_TYPES</constant>). Specify both
<constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> and
<constant>V4L2_CTRL_FLAG_NEXT_COMPOUND</constant> in order to enumerate
all controls, compound or not. Drivers which do not support these flags yet
always return <errorcode>EINVAL</errorcode>.</para>
<para>The <constant>VIDIOC_QUERY_EXT_CTRL</constant> ioctl was
introduced in order to better support controls that can use compound
types, and to expose additional control information that cannot be
returned in &v4l2-queryctrl; since that structure is full.</para>
<para><constant>VIDIOC_QUERY_EXT_CTRL</constant> is used in the
same way as <constant>VIDIOC_QUERYCTRL</constant>, except that the
<structfield>reserved</structfield> array must be zeroed as well.</para>
<para>Additional information is required for menu controls: the
names of the menu items. To query them applications set the
......@@ -142,38 +165,23 @@ string. This information is intended for the user.</entry>
<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 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>
bound for the control. See &v4l2-ctrl-type; how the minimum value is to
be used for each possible control type. Note that this a signed 32-bit 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_BITMASK</constant> controls it is the
set of usable bits.
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>
bound for the control. See &v4l2-ctrl-type; how the maximum value is to
be used for each possible control type. Note that this a signed 32-bit 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
<entry><para>This field gives a step size for the control.
See &v4l2-ctrl-type; how the step value is to be used for each possible
control type. Note that this an unsigned 32-bit value.
</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
......@@ -192,10 +200,11 @@ be always positive.</para></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>
<constant>_BOOLEAN</constant>, <constant>_BITMASK</constant>,
<constant>_MENU</constant> or <constant>_INTEGER_MENU</constant> control.
Not valid for other types of controls.
Note that drivers reset controls to their default value only when the
driver is first loaded, never afterwards.</entry>
</row>
<row>
<entry>__u32</entry>
......@@ -213,6 +222,125 @@ the array to zero.</entry>
</tgroup>
</table>
<table pgwide="1" frame="none" id="v4l2-query-ext-ctrl">
<title>struct <structname>v4l2_query_ext_ctrl</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 <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> the driver clears the
flag and returns the first non-compound control with a higher ID. When the
ID is ORed with <constant>V4L2_CTRL_FLAG_NEXT_COMPOUND</constant> the driver
clears the flag and returns the first compound control with a higher ID.
Set both to get the first control (compound or not) with a higher ID.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>type</structfield></entry>
<entry>Type of control, see <xref
linkend="v4l2-ctrl-type" />.</entry>
</row>
<row>
<entry>char</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>__s64</entry>
<entry><structfield>minimum</structfield></entry>
<entry>Minimum value, inclusive. This field gives a lower
bound for the control. See &v4l2-ctrl-type; how the minimum value is to
be used for each possible control type. Note that this a signed 64-bit value.</entry>
</row>
<row>
<entry>__s64</entry>
<entry><structfield>maximum</structfield></entry>
<entry>Maximum value, inclusive. This field gives an upper
bound for the control. See &v4l2-ctrl-type; how the maximum value is to
be used for each possible control type. Note that this a signed 64-bit value.</entry>
</row>
<row>
<entry>__u64</entry>
<entry><structfield>step</structfield></entry>
<entry><para>This field gives a step size for the control.
See &v4l2-ctrl-type; how the step value is to be used for each possible
control type. Note that this an unsigned 64-bit value.
</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></entry>
</row>
<row>
<entry>__s64</entry>
<entry><structfield>default_value</structfield></entry>
<entry>The default value of a
<constant>V4L2_CTRL_TYPE_INTEGER</constant>, <constant>_INTEGER64</constant>,
<constant>_BOOLEAN</constant>, <constant>_BITMASK</constant>,
<constant>_MENU</constant> or <constant>_INTEGER_MENU</constant> control.
Not valid for other types of controls.
Note that drivers reset controls to their default value only when the
driver is first loaded, never afterwards.
</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>elem_size</structfield></entry>
<entry>The size in bytes of a single element of the array.
Given a char pointer <constant>p</constant> to a 3-dimensional array you can find the
position of cell <constant>(z, y, x)</constant> as follows:
<constant>p + ((z * dims[1] + y) * dims[0] + x) * elem_size</constant>. <structfield>elem_size</structfield>
is always valid, also when the control isn't an array. For string controls
<structfield>elem_size</structfield> is equal to <structfield>maximum + 1</structfield>.
</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>elems</structfield></entry>
<entry>The number of elements in the N-dimensional array. If this control
is not an array, then <structfield>elems</structfield> is 1. The <structfield>elems</structfield>
field can never be 0.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>nr_of_dims</structfield></entry>
<entry>The number of dimension in the N-dimensional array. If this control
is not an array, then this field is 0.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>dims[V4L2_CTRL_MAX_DIMS]</structfield></entry>
<entry>The size of each dimension. The first <structfield>nr_of_dims</structfield>
elements of this array must be non-zero, all remaining elements must be zero.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>reserved</structfield>[32]</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-querymenu">
<title>struct <structname>v4l2_querymenu</structname></title>
<tgroup cols="4">
......@@ -347,11 +475,14 @@ Drivers must ignore the value passed with
</row>
<row>
<entry><constant>V4L2_CTRL_TYPE_INTEGER64</constant></entry>
<entry>n/a</entry>
<entry>n/a</entry>
<entry>n/a</entry>
<entry>any</entry>
<entry>any</entry>
<entry>any</entry>
<entry>A 64-bit integer valued control. Minimum, maximum
and step size cannot be queried.</entry>
and step size cannot be queried using <constant>VIDIOC_QUERYCTRL</constant>.
Only <constant>VIDIOC_QUERY_EXT_CTRL</constant> can retrieve the 64-bit
min/max/step values, they should be interpreted as n/a when using
<constant>VIDIOC_QUERYCTRL</constant>.</entry>
</row>
<row>
<entry><constant>V4L2_CTRL_TYPE_STRING</constant></entry>
......@@ -450,6 +581,14 @@ is in auto-gain mode. In such a case the hardware calculates the gain value base
the lighting conditions which can change over time. Note that setting a new value for
a volatile control will have no effect. The new value will just be ignored.</entry>
</row>
<row>
<entry><constant>V4L2_CTRL_FLAG_HAS_PAYLOAD</constant></entry>
<entry>0x0100</entry>
<entry>This control has a pointer type, so its value has to be accessed
using one of the pointer fields of &v4l2-ext-control;. This flag is set for controls
that are an array, string, or have a compound type. In all cases you have to set a
pointer to memory containing the payload of the control.</entry>
</row>
</tbody>
</tgroup>
</table>
......
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