testcases/kernel/device-drivers/v4l/user_space/doc/spec/r13317.htm - platform/external/ltp - Gitiles

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 >ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU</H1
 ><DIV
 CLASS="REFNAMEDIV"
 ><A
 NAME="AEN13321"
 ></A
 ><H2
 >Name</H2
 >VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU&nbsp;--&nbsp;Enumerate controls and menu control items</DIV
 ><DIV
 CLASS="REFSYNOPSISDIV"
 ><A
 NAME="AEN13325"
 ></A
 ><H2
 >Synopsis</H2
 ><DIV
 CLASS="FUNCSYNOPSIS"
 ><P
 ></P
 ><A
 NAME="AEN13326"
 ></A
 ><P
 ><CODE
 ><CODE
 CLASS="FUNCDEF"
 >int ioctl</CODE
 >(int fd, int request, struct v4l2_queryctrl *argp);</CODE
 ></P
 ><P
 ></P
 ></DIV
 ><DIV
 CLASS="FUNCSYNOPSIS"
 ><P
 ></P
 ><A
 NAME="AEN13336"
 ></A
 ><P
 ><CODE
 ><CODE
 CLASS="FUNCDEF"
 >int ioctl</CODE
 >(int fd, int request, struct v4l2_querymenu *argp);</CODE
 ></P
 ><P
 ></P
 ></DIV
 ></DIV
 ><DIV
 CLASS="REFSECT1"
 ><A
 NAME="AEN13346"
 ></A
 ><H2
 >Arguments</H2
 ><P
 ></P
 ><DIV
 CLASS="VARIABLELIST"
 ><DL
 ><DT
 ><CODE
 CLASS="PARAMETER"
 >fd</CODE
 ></DT
 ><DD
 ><P
 >File descriptor returned by <A
 HREF="r14090.htm"
 ><CODE
 CLASS="FUNCTION"
 >open()</CODE
 ></A
 >.</P
 ></DD
 ><DT
 ><CODE
 CLASS="PARAMETER"
 >request</CODE
 ></DT
 ><DD
 ><P
 >VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU</P
 ></DD
 ><DT
 ><CODE
 CLASS="PARAMETER"
 >argp</CODE
 ></DT
 ><DD
 ><P
 ></P
 ></DD
 ></DL
 ></DIV
 ></DIV
 ><DIV
 CLASS="REFSECT1"
 ><A
 NAME="AEN13366"
 ></A
 ><H2
 >Description</H2
 ><P
 >To query the attributes of a control applications set the
 <CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 > field of a struct&nbsp;<A
 HREF="r13317.htm#V4L2-QUERYCTRL"
 >v4l2_queryctrl</A
 > and call the
 <CODE
 CLASS="CONSTANT"
 >VIDIOC_QUERYCTRL</CODE
 > ioctl with a pointer to this
 structure. The driver fills the rest of the structure or returns an
 <SPAN
 CLASS="ERRORCODE"
 >EINVAL</SPAN
 > error code when the <CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 > is invalid.</P
 ><P
 >It is possible to enumerate controls by calling
 <CODE
 CLASS="CONSTANT"
 >VIDIOC_QUERYCTRL</CODE
 > with successive
 <CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 > values starting from
 <CODE
 CLASS="CONSTANT"
 >V4L2_CID_BASE</CODE
 > up to and exclusive
 <CODE
 CLASS="CONSTANT"
 >V4L2_CID_BASE_LASTP1</CODE
 >. Drivers may return
 <SPAN
 CLASS="ERRORCODE"
 >EINVAL</SPAN
 > 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
 <CODE
 CLASS="CONSTANT"
 >V4L2_CID_PRIVATE_BASE</CODE
 > and incrementing
 <CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 > until the driver returns
 <SPAN
 CLASS="ERRORCODE"
 >EINVAL</SPAN
 >.</P
 ><P
 >In both cases, when the driver sets the
 <CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_FLAG_DISABLED</CODE
 > flag in the
 <CODE
 CLASS="STRUCTFIELD"
 >flags</CODE
 > field this control is permanently
 disabled and should be ignored by the application.<A
 NAME="AEN13386"
 HREF="r13317.htm#FTN.AEN13386"
 ><SPAN
 CLASS="footnote"
 >[1]</SPAN
 ></A
 ></P
 ><P
 >When the application ORs <CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 > with
 <CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_FLAG_NEXT_CTRL</CODE
 > the driver returns the
 next supported control, or <SPAN
 CLASS="ERRORCODE"
 >EINVAL</SPAN
 > if there is
 none. Drivers which do not support this flag yet always return
 <SPAN
 CLASS="ERRORCODE"
 >EINVAL</SPAN
 >.</P
 ><P
 >Additional information is required for menu controls, the
 name of menu items. To query them applications set the
 <CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 > and <CODE
 CLASS="STRUCTFIELD"
 >index</CODE
 >
 fields of struct&nbsp;<A
 HREF="r13317.htm#V4L2-QUERYMENU"
 >v4l2_querymenu</A
 > and call the
 <CODE
 CLASS="CONSTANT"
 >VIDIOC_QUERYMENU</CODE
 > ioctl with a pointer to this
 structure. The driver fills the rest of the structure or returns an
 <SPAN
 CLASS="ERRORCODE"
 >EINVAL</SPAN
 > error code when the <CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 > or
 <CODE
 CLASS="STRUCTFIELD"
 >index</CODE
 > is invalid. Menu items are enumerated
 by calling <CODE
 CLASS="CONSTANT"
 >VIDIOC_QUERYMENU</CODE
 > with successive
 <CODE
 CLASS="STRUCTFIELD"
 >index</CODE
 > values from struct&nbsp;<A
 HREF="r13317.htm#V4L2-QUERYCTRL"
 >v4l2_queryctrl</A
 >
 <CODE
 CLASS="STRUCTFIELD"
 >minimum</CODE
 > (0) to
 <CODE
 CLASS="STRUCTFIELD"
 >maximum</CODE
 >, inclusive.</P
 ><P
 >See also the examples in <A
 HREF="x542.htm"
 >Section 1.8</A
 >.</P
 ><DIV
 CLASS="TABLE"
 ><A
 NAME="V4L2-QUERYCTRL"
 ></A
 ><P
 ><B
 >Table 1. struct <CODE
 CLASS="STRUCTNAME"
 >v4l2_queryctrl</CODE
 ></B
 ></P
 ><TABLE
 BORDER="0"
 FRAME="void"
 WIDTH="100%"
 CLASS="CALSTABLE"
 ><COL
 WIDTH="25%"
 TITLE="C1"><COL
 WIDTH="25%"
 TITLE="C2"><COL
 WIDTH="50%"
 TITLE="C3"><TBODY
 VALIGN="TOP"
 ><TR
 ><TD
 >__u32</TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 ></TD
 ><TD
 >Identifies the control, set by the application. See
 <A
 HREF="x542.htm#CONTROL-ID"
 >Table 1-1</A
 > 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 <SPAN
 CLASS="ERRORCODE"
 >EINVAL</SPAN
 > error code.</TD
 ></TR
 ><TR
 ><TD
 >enum&nbsp;<A
 HREF="r13317.htm#V4L2-CTRL-TYPE"
 >v4l2_ctrl_type</A
 ></TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >type</CODE
 ></TD
 ><TD
 >Type of control, see <A
 HREF="r13317.htm#V4L2-CTRL-TYPE"
 >Table 3</A
 >.</TD
 ></TR
 ><TR
 ><TD
 >__u8</TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >name</CODE
 >[32]</TD
 ><TD
 >Name of the control, a NUL-terminated ASCII
 string. This information is intended for the user.</TD
 ></TR
 ><TR
 ><TD
 >__s32</TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >minimum</CODE
 ></TD
 ><TD
 >Minimum value, inclusive. This field gives a lower
 bound for <CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_INTEGER</CODE
 > controls. It may
 not be valid for any other type of control, including
 <CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_INTEGER64</CODE
 > controls. Note this is a
 signed value.</TD
 ></TR
 ><TR
 ><TD
 >__s32</TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >maximum</CODE
 ></TD
 ><TD
 >Maximum value, inclusive. This field gives an upper
 bound for <CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_INTEGER</CODE
 > controls and the
 highest valid index for <CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_MENU</CODE
 >
 controls. It may not be valid for any other type of control, including
 <CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_INTEGER64</CODE
 > controls. Note this is a
 signed value.</TD
 ></TR
 ><TR
 ><TD
 >__s32</TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >step</CODE
 ></TD
 ><TD
 ><P
 >This field gives a step size for
 <CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_INTEGER</CODE
 > controls. It may not be
 valid for any other type of control, including
 <CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_INTEGER64</CODE
 >
 controls.</P
 ><P
 >Generally drivers should not scale hardware
 control values. It may be necessary for example when the
 <CODE
 CLASS="STRUCTFIELD"
 >name</CODE
 > or <CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 > 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.</P
 ><P
 >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.</P
 ><P
 >Note although signed, the step value is supposed to
 be always positive.</P
 ></TD
 ></TR
 ><TR
 ><TD
 >__s32</TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >default_value</CODE
 ></TD
 ><TD
 >The default value of a
 <CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_INTEGER</CODE
 >,
 <CODE
 CLASS="CONSTANT"
 >_BOOLEAN</CODE
 > or <CODE
 CLASS="CONSTANT"
 >_MENU</CODE
 > 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.</TD
 ></TR
 ><TR
 ><TD
 >__u32</TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >flags</CODE
 ></TD
 ><TD
 >Control flags, see <A
 HREF="r13317.htm#CONTROL-FLAGS"
 >Table 4</A
 >.</TD
 ></TR
 ><TR
 ><TD
 >__u32</TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >reserved</CODE
 >[2]</TD
 ><TD
 >Reserved for future extensions. Drivers must set
 the array to zero.</TD
 ></TR
 ></TBODY
 ></TABLE
 ></DIV
 ><DIV
 CLASS="TABLE"
 ><A
 NAME="V4L2-QUERYMENU"
 ></A
 ><P
 ><B
 >Table 2. struct <CODE
 CLASS="STRUCTNAME"
 >v4l2_querymenu</CODE
 ></B
 ></P
 ><TABLE
 BORDER="0"
 FRAME="void"
 WIDTH="100%"
 CLASS="CALSTABLE"
 ><COL
 WIDTH="25%"
 TITLE="C1"><COL
 WIDTH="25%"
 TITLE="C2"><COL
 WIDTH="50%"
 TITLE="C3"><TBODY
 VALIGN="TOP"
 ><TR
 ><TD
 >__u32</TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 ></TD
 ><TD
 >Identifies the control, set by the application
 from the respective struct&nbsp;<A
 HREF="r13317.htm#V4L2-QUERYCTRL"
 >v4l2_queryctrl</A
 >
 <CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 >.</TD
 ></TR
 ><TR
 ><TD
 >__u32</TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >index</CODE
 ></TD
 ><TD
 >Index of the menu item, starting at zero, set by
             the application.</TD
 ></TR
 ><TR
 ><TD
 >__u8</TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >name</CODE
 >[32]</TD
 ><TD
 >Name of the menu item, a NUL-terminated ASCII
 string. This information is intended for the user.</TD
 ></TR
 ><TR
 ><TD
 >__u32</TD
 ><TD
 ><CODE
 CLASS="STRUCTFIELD"
 >reserved</CODE
 ></TD
 ><TD
 >Reserved for future extensions. Drivers must set
 the array to zero.</TD
 ></TR
 ></TBODY
 ></TABLE
 ></DIV
 ><DIV
 CLASS="TABLE"
 ><A
 NAME="V4L2-CTRL-TYPE"
 ></A
 ><P
 ><B
 >Table 3. enum v4l2_ctrl_type</B
 ></P
 ><TABLE
 BORDER="0"
 FRAME="void"
 WIDTH="100%"
 CLASS="CALSTABLE"
 ><COL
 WIDTH="30%"><COL
 WIDTH="5%"
 ALIGN="CENTER"><COL
 WIDTH="5%"
 ALIGN="CENTER"><COL
 WIDTH="5%"
 ALIGN="CENTER"><COL
 WIDTH="55%"><THEAD
 ><TR
 ><TH
 >Type</TH
 ><TH
 ><CODE
 CLASS="STRUCTFIELD"
 >minimum</CODE
 ></TH
 ><TH
 ><CODE
 CLASS="STRUCTFIELD"
 >step</CODE
 ></TH
 ><TH
 ><CODE
 CLASS="STRUCTFIELD"
 >maximum</CODE
 ></TH
 ><TH
 >Description</TH
 ></TR
 ></THEAD
 ><TBODY
 VALIGN="TOP"
 ><TR
 ><TD
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_INTEGER</CODE
 ></TD
 ><TD
 >any</TD
 ><TD
 >any</TD
 ><TD
 >any</TD
 ><TD
 >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.</TD
 ></TR
 ><TR
 ><TD
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_BOOLEAN</CODE
 ></TD
 ><TD
 >0</TD
 ><TD
 >1</TD
 ><TD
 >1</TD
 ><TD
 >A boolean-valued control. Zero corresponds to
 "disabled", and one means "enabled".</TD
 ></TR
 ><TR
 ><TD
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_MENU</CODE
 ></TD
 ><TD
 >0</TD
 ><TD
 >1</TD
 ><TD
 >N-1</TD
 ><TD
 >The control has a menu of N choices. The names of
 the menu items can be enumerated with the
 <CODE
 CLASS="CONSTANT"
 >VIDIOC_QUERYMENU</CODE
 > ioctl.</TD
 ></TR
 ><TR
 ><TD
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_BUTTON</CODE
 ></TD
 ><TD
 >0</TD
 ><TD
 >0</TD
 ><TD
 >0</TD
 ><TD
 >A control which performs an action when set.
 Drivers must ignore the value passed with
 <CODE
 CLASS="CONSTANT"
 >VIDIOC_S_CTRL</CODE
 > and return an <SPAN
 CLASS="ERRORCODE"
 >EINVAL</SPAN
 > error code on a
 <CODE
 CLASS="CONSTANT"
 >VIDIOC_G_CTRL</CODE
 > attempt.</TD
 ></TR
 ><TR
 ><TD
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_INTEGER64</CODE
 ></TD
 ><TD
 >n/a</TD
 ><TD
 >n/a</TD
 ><TD
 >n/a</TD
 ><TD
 >A 64-bit integer valued control. Minimum, maximum
 and step size cannot be queried.</TD
 ></TR
 ><TR
 ><TD
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_TYPE_CTRL_CLASS</CODE
 ></TD
 ><TD
 >n/a</TD
 ><TD
 >n/a</TD
 ><TD
 >n/a</TD
 ><TD
 >This is not a control. When
 <CODE
 CLASS="CONSTANT"
 >VIDIOC_QUERYCTRL</CODE
 > is called with a control ID
 equal to a control class code (see <A
 HREF="r10386.htm#CTRL-CLASS"
 >Table 3</A
 >), the
 ioctl returns the name of the control class and this control type.
 Older drivers which do not support this feature return an
 <SPAN
 CLASS="ERRORCODE"
 >EINVAL</SPAN
 > error code.</TD
 ></TR
 ></TBODY
 ></TABLE
 ></DIV
 ><DIV
 CLASS="TABLE"
 ><A
 NAME="CONTROL-FLAGS"
 ></A
 ><P
 ><B
 >Table 4. Control Flags</B
 ></P
 ><TABLE
 BORDER="0"
 FRAME="void"
 WIDTH="100%"
 CLASS="CALSTABLE"
 ><COL
 WIDTH="38%"
 TITLE="C1"><COL
 WIDTH="12%"
 TITLE="C2"><COL
 WIDTH="50%"
 TITLE="C3"><TBODY
 VALIGN="TOP"
 ><TR
 ><TD
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_FLAG_DISABLED</CODE
 ></TD
 ><TD
 >0x0001</TD
 ><TD
 >This control is permanently disabled and should be
 ignored by the application. Any attempt to change the control will
 result in an <SPAN
 CLASS="ERRORCODE"
 >EINVAL</SPAN
 > error code.</TD
 ></TR
 ><TR
 ><TD
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_FLAG_GRABBED</CODE
 ></TD
 ><TD
 >0x0002</TD
 ><TD
 >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
 <SPAN
 CLASS="ERRORCODE"
 >EBUSY</SPAN
 > error code.</TD
 ></TR
 ><TR
 ><TD
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_FLAG_READ_ONLY</CODE
 ></TD
 ><TD
 >0x0004</TD
 ><TD
 >This control is permanently readable only. Any
 attempt to change the control will result in an <SPAN
 CLASS="ERRORCODE"
 >EINVAL</SPAN
 > error code.</TD
 ></TR
 ><TR
 ><TD
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_FLAG_UPDATE</CODE
 ></TD
 ><TD
 >0x0008</TD
 ><TD
 >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.</TD
 ></TR
 ><TR
 ><TD
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_FLAG_INACTIVE</CODE
 ></TD
 ><TD
 >0x0010</TD
 ><TD
 >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.</TD
 ></TR
 ><TR
 ><TD
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_FLAG_SLIDER</CODE
 ></TD
 ><TD
 >0x0020</TD
 ><TD
 >A hint that this control is best represented as a
 slider-like element in a user interface.</TD
 ></TR
 ></TBODY
 ></TABLE
 ></DIV
 ></DIV
 ><DIV
 CLASS="REFSECT1"
 ><A
 NAME="AEN13624"
 ></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
 ><P
 ></P
 ><DIV
 CLASS="VARIABLELIST"
 ><DL
 ><DT
 ><SPAN
 CLASS="ERRORCODE"
 >EINVAL</SPAN
 ></DT
 ><DD
 ><P
 >The struct&nbsp;<A
 HREF="r13317.htm#V4L2-QUERYCTRL"
 >v4l2_queryctrl</A
 > <CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 >
 is invalid. The struct&nbsp;<A
 HREF="r13317.htm#V4L2-QUERYMENU"
 >v4l2_querymenu</A
 > <CODE
 CLASS="STRUCTFIELD"
 >id</CODE
 > or
 <CODE
 CLASS="STRUCTFIELD"
 >index</CODE
 > is invalid.</P
 ></DD
 ></DL
 ></DIV
 ></DIV
 ><H2
 CLASS="FOOTNOTES"
 >Notes</H2
 ><TABLE
 BORDER="0"
 CLASS="FOOTNOTES"
 WIDTH="100%"
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 WIDTH="5%"
 ><A
 NAME="FTN.AEN13386"
 HREF="r13317.htm#AEN13386"
 ><SPAN
 CLASS="footnote"
 >[1]</SPAN
 ></A
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 WIDTH="95%"
 ><P
 ><CODE
 CLASS="CONSTANT"
 >V4L2_CTRL_FLAG_DISABLED</CODE
 > 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).</P
 ></TD
 ></TR
 ></TABLE
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 CLASS="NAVFOOTER"
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	>Video for Linux Two API Specification: Revision 0.24</TH
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	><H1
	><A
	NAME="VIDIOC-QUERYCTRL"
	></A
	>ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU</H1
	><DIV
	CLASS="REFNAMEDIV"
	><A
	NAME="AEN13321"
	></A
	><H2
	>Name</H2
	>VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU -- Enumerate controls and menu control items</DIV
	><DIV
	CLASS="REFSYNOPSISDIV"
	><A
	NAME="AEN13325"
	></A
	><H2
	>Synopsis</H2
	><DIV
	CLASS="FUNCSYNOPSIS"
	><P
	></P
	><A
	NAME="AEN13326"
	></A
	><P
	><CODE
	><CODE
	CLASS="FUNCDEF"
	>int ioctl</CODE
	>(int fd, int request, struct v4l2_queryctrl *argp);</CODE
	></P
	><P
	></P
	></DIV
	><DIV
	CLASS="FUNCSYNOPSIS"
	><P
	></P
	><A
	NAME="AEN13336"
	></A
	><P
	><CODE
	><CODE
	CLASS="FUNCDEF"
	>int ioctl</CODE
	>(int fd, int request, struct v4l2_querymenu *argp);</CODE
	></P
	><P
	></P
	></DIV
	></DIV
	><DIV
	CLASS="REFSECT1"
	><A
	NAME="AEN13346"
	></A
	><H2
	>Arguments</H2
	><P
	></P
	><DIV
	CLASS="VARIABLELIST"
	><DL
	><DT
	><CODE
	CLASS="PARAMETER"
	>fd</CODE
	></DT
	><DD
	><P
	>File descriptor returned by <A
	HREF="r14090.htm"
	><CODE
	CLASS="FUNCTION"
	>open()</CODE
	></A
	>.</P
	></DD
	><DT
	><CODE
	CLASS="PARAMETER"
	>request</CODE
	></DT
	><DD
	><P
	>VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU</P
	></DD
	><DT
	><CODE
	CLASS="PARAMETER"
	>argp</CODE
	></DT
	><DD
	><P
	></P
	></DD
	></DL
	></DIV
	></DIV
	><DIV
	CLASS="REFSECT1"
	><A
	NAME="AEN13366"
	></A
	><H2
	>Description</H2
	><P
	>To query the attributes of a control applications set the
	<CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	> field of a struct <A
	HREF="r13317.htm#V4L2-QUERYCTRL"
	>v4l2_queryctrl</A
	> and call the
	<CODE
	CLASS="CONSTANT"
	>VIDIOC_QUERYCTRL</CODE
	> ioctl with a pointer to this
	structure. The driver fills the rest of the structure or returns an
	<SPAN
	CLASS="ERRORCODE"
	>EINVAL</SPAN
	> error code when the <CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	> is invalid.</P
	><P
	>It is possible to enumerate controls by calling
	<CODE
	CLASS="CONSTANT"
	>VIDIOC_QUERYCTRL</CODE
	> with successive
	<CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	> values starting from
	<CODE
	CLASS="CONSTANT"
	>V4L2_CID_BASE</CODE
	> up to and exclusive
	<CODE
	CLASS="CONSTANT"
	>V4L2_CID_BASE_LASTP1</CODE
	>. Drivers may return
	<SPAN
	CLASS="ERRORCODE"
	>EINVAL</SPAN
	> 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
	<CODE
	CLASS="CONSTANT"
	>V4L2_CID_PRIVATE_BASE</CODE
	> and incrementing
	<CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	> until the driver returns
	<SPAN
	CLASS="ERRORCODE"
	>EINVAL</SPAN
	>.</P
	><P
	>In both cases, when the driver sets the
	<CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_FLAG_DISABLED</CODE
	> flag in the
	<CODE
	CLASS="STRUCTFIELD"
	>flags</CODE
	> field this control is permanently
	disabled and should be ignored by the application.<A
	NAME="AEN13386"
	HREF="r13317.htm#FTN.AEN13386"
	><SPAN
	CLASS="footnote"
	>[1]</SPAN
	></A
	></P
	><P
	>When the application ORs <CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	> with
	<CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_FLAG_NEXT_CTRL</CODE
	> the driver returns the
	next supported control, or <SPAN
	CLASS="ERRORCODE"
	>EINVAL</SPAN
	> if there is
	none. Drivers which do not support this flag yet always return
	<SPAN
	CLASS="ERRORCODE"
	>EINVAL</SPAN
	>.</P
	><P
	>Additional information is required for menu controls, the
	name of menu items. To query them applications set the
	<CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	> and <CODE
	CLASS="STRUCTFIELD"
	>index</CODE
	>
	fields of struct <A
	HREF="r13317.htm#V4L2-QUERYMENU"
	>v4l2_querymenu</A
	> and call the
	<CODE
	CLASS="CONSTANT"
	>VIDIOC_QUERYMENU</CODE
	> ioctl with a pointer to this
	structure. The driver fills the rest of the structure or returns an
	<SPAN
	CLASS="ERRORCODE"
	>EINVAL</SPAN
	> error code when the <CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	> or
	<CODE
	CLASS="STRUCTFIELD"
	>index</CODE
	> is invalid. Menu items are enumerated
	by calling <CODE
	CLASS="CONSTANT"
	>VIDIOC_QUERYMENU</CODE
	> with successive
	<CODE
	CLASS="STRUCTFIELD"
	>index</CODE
	> values from struct <A
	HREF="r13317.htm#V4L2-QUERYCTRL"
	>v4l2_queryctrl</A
	>
	<CODE
	CLASS="STRUCTFIELD"
	>minimum</CODE
	> (0) to
	<CODE
	CLASS="STRUCTFIELD"
	>maximum</CODE
	>, inclusive.</P
	><P
	>See also the examples in <A
	HREF="x542.htm"
	>Section 1.8</A
	>.</P
	><DIV
	CLASS="TABLE"
	><A
	NAME="V4L2-QUERYCTRL"
	></A
	><P
	><B
	>Table 1. struct <CODE
	CLASS="STRUCTNAME"
	>v4l2_queryctrl</CODE
	></B
	></P
	><TABLE
	BORDER="0"
	FRAME="void"
	WIDTH="100%"
	CLASS="CALSTABLE"
	><COL
	WIDTH="25%"
	TITLE="C1"><COL
	WIDTH="25%"
	TITLE="C2"><COL
	WIDTH="50%"
	TITLE="C3"><TBODY
	VALIGN="TOP"
	><TR
	><TD
	>__u32</TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	></TD
	><TD
	>Identifies the control, set by the application. See
	<A
	HREF="x542.htm#CONTROL-ID"
	>Table 1-1</A
	> 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 <SPAN
	CLASS="ERRORCODE"
	>EINVAL</SPAN
	> error code.</TD
	></TR
	><TR
	><TD
	>enum <A
	HREF="r13317.htm#V4L2-CTRL-TYPE"
	>v4l2_ctrl_type</A
	></TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>type</CODE
	></TD
	><TD
	>Type of control, see <A
	HREF="r13317.htm#V4L2-CTRL-TYPE"
	>Table 3</A
	>.</TD
	></TR
	><TR
	><TD
	>__u8</TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>name</CODE
	>[32]</TD
	><TD
	>Name of the control, a NUL-terminated ASCII
	string. This information is intended for the user.</TD
	></TR
	><TR
	><TD
	>__s32</TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>minimum</CODE
	></TD
	><TD
	>Minimum value, inclusive. This field gives a lower
	bound for <CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_INTEGER</CODE
	> controls. It may
	not be valid for any other type of control, including
	<CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_INTEGER64</CODE
	> controls. Note this is a
	signed value.</TD
	></TR
	><TR
	><TD
	>__s32</TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>maximum</CODE
	></TD
	><TD
	>Maximum value, inclusive. This field gives an upper
	bound for <CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_INTEGER</CODE
	> controls and the
	highest valid index for <CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_MENU</CODE
	>
	controls. It may not be valid for any other type of control, including
	<CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_INTEGER64</CODE
	> controls. Note this is a
	signed value.</TD
	></TR
	><TR
	><TD
	>__s32</TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>step</CODE
	></TD
	><TD
	><P
	>This field gives a step size for
	<CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_INTEGER</CODE
	> controls. It may not be
	valid for any other type of control, including
	<CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_INTEGER64</CODE
	>
	controls.</P
	><P
	>Generally drivers should not scale hardware
	control values. It may be necessary for example when the
	<CODE
	CLASS="STRUCTFIELD"
	>name</CODE
	> or <CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	> 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.</P
	><P
	>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.</P
	><P
	>Note although signed, the step value is supposed to
	be always positive.</P
	></TD
	></TR
	><TR
	><TD
	>__s32</TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>default_value</CODE
	></TD
	><TD
	>The default value of a
	<CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_INTEGER</CODE
	>,
	<CODE
	CLASS="CONSTANT"
	>_BOOLEAN</CODE
	> or <CODE
	CLASS="CONSTANT"
	>_MENU</CODE
	> 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.</TD
	></TR
	><TR
	><TD
	>__u32</TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>flags</CODE
	></TD
	><TD
	>Control flags, see <A
	HREF="r13317.htm#CONTROL-FLAGS"
	>Table 4</A
	>.</TD
	></TR
	><TR
	><TD
	>__u32</TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>reserved</CODE
	>[2]</TD
	><TD
	>Reserved for future extensions. Drivers must set
	the array to zero.</TD
	></TR
	></TBODY
	></TABLE
	></DIV
	><DIV
	CLASS="TABLE"
	><A
	NAME="V4L2-QUERYMENU"
	></A
	><P
	><B
	>Table 2. struct <CODE
	CLASS="STRUCTNAME"
	>v4l2_querymenu</CODE
	></B
	></P
	><TABLE
	BORDER="0"
	FRAME="void"
	WIDTH="100%"
	CLASS="CALSTABLE"
	><COL
	WIDTH="25%"
	TITLE="C1"><COL
	WIDTH="25%"
	TITLE="C2"><COL
	WIDTH="50%"
	TITLE="C3"><TBODY
	VALIGN="TOP"
	><TR
	><TD
	>__u32</TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	></TD
	><TD
	>Identifies the control, set by the application
	from the respective struct <A
	HREF="r13317.htm#V4L2-QUERYCTRL"
	>v4l2_queryctrl</A
	>
	<CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	>.</TD
	></TR
	><TR
	><TD
	>__u32</TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>index</CODE
	></TD
	><TD
	>Index of the menu item, starting at zero, set by
	the application.</TD
	></TR
	><TR
	><TD
	>__u8</TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>name</CODE
	>[32]</TD
	><TD
	>Name of the menu item, a NUL-terminated ASCII
	string. This information is intended for the user.</TD
	></TR
	><TR
	><TD
	>__u32</TD
	><TD
	><CODE
	CLASS="STRUCTFIELD"
	>reserved</CODE
	></TD
	><TD
	>Reserved for future extensions. Drivers must set
	the array to zero.</TD
	></TR
	></TBODY
	></TABLE
	></DIV
	><DIV
	CLASS="TABLE"
	><A
	NAME="V4L2-CTRL-TYPE"
	></A
	><P
	><B
	>Table 3. enum v4l2_ctrl_type</B
	></P
	><TABLE
	BORDER="0"
	FRAME="void"
	WIDTH="100%"
	CLASS="CALSTABLE"
	><COL
	WIDTH="30%"><COL
	WIDTH="5%"
	ALIGN="CENTER"><COL
	WIDTH="5%"
	ALIGN="CENTER"><COL
	WIDTH="5%"
	ALIGN="CENTER"><COL
	WIDTH="55%"><THEAD
	><TR
	><TH
	>Type</TH
	><TH
	><CODE
	CLASS="STRUCTFIELD"
	>minimum</CODE
	></TH
	><TH
	><CODE
	CLASS="STRUCTFIELD"
	>step</CODE
	></TH
	><TH
	><CODE
	CLASS="STRUCTFIELD"
	>maximum</CODE
	></TH
	><TH
	>Description</TH
	></TR
	></THEAD
	><TBODY
	VALIGN="TOP"
	><TR
	><TD
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_INTEGER</CODE
	></TD
	><TD
	>any</TD
	><TD
	>any</TD
	><TD
	>any</TD
	><TD
	>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.</TD
	></TR
	><TR
	><TD
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_BOOLEAN</CODE
	></TD
	><TD
	>0</TD
	><TD
	>1</TD
	><TD
	>1</TD
	><TD
	>A boolean-valued control. Zero corresponds to
	"disabled", and one means "enabled".</TD
	></TR
	><TR
	><TD
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_MENU</CODE
	></TD
	><TD
	>0</TD
	><TD
	>1</TD
	><TD
	>N-1</TD
	><TD
	>The control has a menu of N choices. The names of
	the menu items can be enumerated with the
	<CODE
	CLASS="CONSTANT"
	>VIDIOC_QUERYMENU</CODE
	> ioctl.</TD
	></TR
	><TR
	><TD
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_BUTTON</CODE
	></TD
	><TD
	>0</TD
	><TD
	>0</TD
	><TD
	>0</TD
	><TD
	>A control which performs an action when set.
	Drivers must ignore the value passed with
	<CODE
	CLASS="CONSTANT"
	>VIDIOC_S_CTRL</CODE
	> and return an <SPAN
	CLASS="ERRORCODE"
	>EINVAL</SPAN
	> error code on a
	<CODE
	CLASS="CONSTANT"
	>VIDIOC_G_CTRL</CODE
	> attempt.</TD
	></TR
	><TR
	><TD
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_INTEGER64</CODE
	></TD
	><TD
	>n/a</TD
	><TD
	>n/a</TD
	><TD
	>n/a</TD
	><TD
	>A 64-bit integer valued control. Minimum, maximum
	and step size cannot be queried.</TD
	></TR
	><TR
	><TD
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_TYPE_CTRL_CLASS</CODE
	></TD
	><TD
	>n/a</TD
	><TD
	>n/a</TD
	><TD
	>n/a</TD
	><TD
	>This is not a control. When
	<CODE
	CLASS="CONSTANT"
	>VIDIOC_QUERYCTRL</CODE
	> is called with a control ID
	equal to a control class code (see <A
	HREF="r10386.htm#CTRL-CLASS"
	>Table 3</A
	>), the
	ioctl returns the name of the control class and this control type.
	Older drivers which do not support this feature return an
	<SPAN
	CLASS="ERRORCODE"
	>EINVAL</SPAN
	> error code.</TD
	></TR
	></TBODY
	></TABLE
	></DIV
	><DIV
	CLASS="TABLE"
	><A
	NAME="CONTROL-FLAGS"
	></A
	><P
	><B
	>Table 4. Control Flags</B
	></P
	><TABLE
	BORDER="0"
	FRAME="void"
	WIDTH="100%"
	CLASS="CALSTABLE"
	><COL
	WIDTH="38%"
	TITLE="C1"><COL
	WIDTH="12%"
	TITLE="C2"><COL
	WIDTH="50%"
	TITLE="C3"><TBODY
	VALIGN="TOP"
	><TR
	><TD
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_FLAG_DISABLED</CODE
	></TD
	><TD
	>0x0001</TD
	><TD
	>This control is permanently disabled and should be
	ignored by the application. Any attempt to change the control will
	result in an <SPAN
	CLASS="ERRORCODE"
	>EINVAL</SPAN
	> error code.</TD
	></TR
	><TR
	><TD
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_FLAG_GRABBED</CODE
	></TD
	><TD
	>0x0002</TD
	><TD
	>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
	<SPAN
	CLASS="ERRORCODE"
	>EBUSY</SPAN
	> error code.</TD
	></TR
	><TR
	><TD
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_FLAG_READ_ONLY</CODE
	></TD
	><TD
	>0x0004</TD
	><TD
	>This control is permanently readable only. Any
	attempt to change the control will result in an <SPAN
	CLASS="ERRORCODE"
	>EINVAL</SPAN
	> error code.</TD
	></TR
	><TR
	><TD
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_FLAG_UPDATE</CODE
	></TD
	><TD
	>0x0008</TD
	><TD
	>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.</TD
	></TR
	><TR
	><TD
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_FLAG_INACTIVE</CODE
	></TD
	><TD
	>0x0010</TD
	><TD
	>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.</TD
	></TR
	><TR
	><TD
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_FLAG_SLIDER</CODE
	></TD
	><TD
	>0x0020</TD
	><TD
	>A hint that this control is best represented as a
	slider-like element in a user interface.</TD
	></TR
	></TBODY
	></TABLE
	></DIV
	></DIV
	><DIV
	CLASS="REFSECT1"
	><A
	NAME="AEN13624"
	></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
	><P
	></P
	><DIV
	CLASS="VARIABLELIST"
	><DL
	><DT
	><SPAN
	CLASS="ERRORCODE"
	>EINVAL</SPAN
	></DT
	><DD
	><P
	>The struct <A
	HREF="r13317.htm#V4L2-QUERYCTRL"
	>v4l2_queryctrl</A
	> <CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	>
	is invalid. The struct <A
	HREF="r13317.htm#V4L2-QUERYMENU"
	>v4l2_querymenu</A
	> <CODE
	CLASS="STRUCTFIELD"
	>id</CODE
	> or
	<CODE
	CLASS="STRUCTFIELD"
	>index</CODE
	> is invalid.</P
	></DD
	></DL
	></DIV
	></DIV
	><H2
	CLASS="FOOTNOTES"
	>Notes</H2
	><TABLE
	BORDER="0"
	CLASS="FOOTNOTES"
	WIDTH="100%"
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	WIDTH="5%"
	><A
	NAME="FTN.AEN13386"
	HREF="r13317.htm#AEN13386"
	><SPAN
	CLASS="footnote"
	>[1]</SPAN
	></A
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	WIDTH="95%"
	><P
	><CODE
	CLASS="CONSTANT"
	>V4L2_CTRL_FLAG_DISABLED</CODE
	> 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).</P
	></TD
	></TR
	></TABLE
	><DIV
	CLASS="NAVFOOTER"
	><HR
	ALIGN="LEFT"
	WIDTH="100%"><TABLE
	SUMMARY="Footer navigation table"
	WIDTH="100%"
	BORDER="0"
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