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| >Video for Linux Two API Specification: Revision 0.24</TH |
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| ><TR |
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| ><H1 |
| ><A |
| NAME="VIDIOC-QUERYCAP" |
| ></A |
| >ioctl VIDIOC_QUERYCAP</H1 |
| ><DIV |
| CLASS="REFNAMEDIV" |
| ><A |
| NAME="AEN13109" |
| ></A |
| ><H2 |
| >Name</H2 |
| >VIDIOC_QUERYCAP -- Query device capabilities</DIV |
| ><DIV |
| CLASS="REFSYNOPSISDIV" |
| ><A |
| NAME="AEN13112" |
| ></A |
| ><H2 |
| >Synopsis</H2 |
| ><DIV |
| CLASS="FUNCSYNOPSIS" |
| ><P |
| ></P |
| ><A |
| NAME="AEN13113" |
| ></A |
| ><P |
| ><CODE |
| ><CODE |
| CLASS="FUNCDEF" |
| >int ioctl</CODE |
| >(int fd, int request, struct v4l2_capability *argp);</CODE |
| ></P |
| ><P |
| ></P |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN13123" |
| ></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_QUERYCAP</P |
| ></DD |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >argp</CODE |
| ></DT |
| ><DD |
| ><P |
| ></P |
| ></DD |
| ></DL |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN13143" |
| ></A |
| ><H2 |
| >Description</H2 |
| ><P |
| >All V4L2 devices support the |
| <CODE |
| CLASS="CONSTANT" |
| >VIDIOC_QUERYCAP</CODE |
| > ioctl. It is used to identify |
| kernel devices compatible with this specification and to obtain |
| information about driver and hardware capabilities. The ioctl takes a |
| pointer to a struct <A |
| HREF="r13105.htm#V4L2-CAPABILITY" |
| >v4l2_capability</A |
| > which is filled by the driver. When the |
| driver is not compatible with this specification the ioctl returns an |
| <SPAN |
| CLASS="ERRORCODE" |
| >EINVAL</SPAN |
| > error code.</P |
| ><DIV |
| CLASS="TABLE" |
| ><A |
| NAME="V4L2-CAPABILITY" |
| ></A |
| ><P |
| ><B |
| >Table 1. struct <CODE |
| CLASS="STRUCTNAME" |
| >v4l2_capability</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 |
| >__u8</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >driver</CODE |
| >[16]</TD |
| ><TD |
| ><P |
| >Name of the driver, a unique NUL-terminated |
| ASCII string. For example: "bttv". Driver specific applications can |
| use this information to verify the driver identity. It is also useful |
| to work around known bugs, or to identify drivers in error reports. |
| The driver version is stored in the <CODE |
| CLASS="STRUCTFIELD" |
| >version</CODE |
| > |
| field.</P |
| ><P |
| >Storing strings in fixed sized arrays is bad |
| practice but unavoidable here. Drivers and applications should take |
| precautions to never read or write beyond the end of the array and to |
| make sure the strings are properly NUL-terminated.</P |
| ></TD |
| ></TR |
| ><TR |
| ><TD |
| >__u8</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >card</CODE |
| >[32]</TD |
| ><TD |
| >Name of the device, a NUL-terminated ASCII string. |
| For example: "Yoyodyne TV/FM". One driver may support different brands |
| or models of video hardware. This information is intended for users, |
| for example in a menu of available devices. Since multiple TV cards of |
| the same brand may be installed which are supported by the same |
| driver, this name should be combined with the character device file |
| name (e. g. <TT |
| CLASS="FILENAME" |
| >/dev/video2</TT |
| >) or the |
| <CODE |
| CLASS="STRUCTFIELD" |
| >bus_info</CODE |
| > string to avoid |
| ambiguities.</TD |
| ></TR |
| ><TR |
| ><TD |
| >__u8</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >bus_info</CODE |
| >[32]</TD |
| ><TD |
| >Location of the device in the system, a |
| NUL-terminated ASCII string. For example: "PCI Slot 4". This |
| information is intended for users, to distinguish multiple |
| identical devices. If no such information is available the field may |
| simply count the devices controlled by the driver, or contain the |
| empty string (<CODE |
| CLASS="STRUCTFIELD" |
| >bus_info</CODE |
| >[0] = 0).</TD |
| ></TR |
| ><TR |
| ><TD |
| >__u32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >version</CODE |
| ></TD |
| ><TD |
| ><P |
| >Version number of the driver. Together with |
| the <CODE |
| CLASS="STRUCTFIELD" |
| >driver</CODE |
| > field this identifies a |
| particular driver. The version number is formatted using the |
| <CODE |
| CLASS="CONSTANT" |
| >KERNEL_VERSION()</CODE |
| > macro:</P |
| ></TD |
| ></TR |
| ><TR |
| ><TD |
| COLSPAN="3" |
| ><P |
| ><PRE |
| CLASS="PROGRAMLISTING" |
| >#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c)) |
| |
| __u32 version = KERNEL_VERSION(0, 8, 1); |
| |
| printf ("Version: %u.%u.%u\n", |
| (version >> 16) & 0xFF, |
| (version >> 8) & 0xFF, |
| version & 0xFF);</PRE |
| ></P |
| ></TD |
| ></TR |
| ><TR |
| ><TD |
| >__u32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >capabilities</CODE |
| ></TD |
| ><TD |
| >Device capabilities, see <A |
| HREF="r13105.htm#DEVICE-CAPABILITIES" |
| >Table 2</A |
| >.</TD |
| ></TR |
| ><TR |
| ><TD |
| >__u32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >reserved</CODE |
| >[4]</TD |
| ><TD |
| >Reserved for future extensions. Drivers must set |
| this array to zero.</TD |
| ></TR |
| ></TBODY |
| ></TABLE |
| ></DIV |
| ><DIV |
| CLASS="TABLE" |
| ><A |
| NAME="DEVICE-CAPABILITIES" |
| ></A |
| ><P |
| ><B |
| >Table 2. Device Capabilities 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_CAP_VIDEO_CAPTURE</CODE |
| ></TD |
| ><TD |
| >0x00000001</TD |
| ><TD |
| >The device supports the <A |
| HREF="c6488.htm#CAPTURE" |
| >Video Capture</A |
| > interface.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_VIDEO_OUTPUT</CODE |
| ></TD |
| ><TD |
| >0x00000002</TD |
| ><TD |
| >The device supports the <A |
| HREF="x6831.htm" |
| >Video Output</A |
| > interface.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_VIDEO_OVERLAY</CODE |
| ></TD |
| ><TD |
| >0x00000004</TD |
| ><TD |
| >The device supports the <A |
| HREF="x6570.htm" |
| >Video Overlay</A |
| > interface. A video overlay device |
| typically stores captured images directly in the video memory of a |
| graphics card, with hardware clipping and scaling.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_VBI_CAPTURE</CODE |
| ></TD |
| ><TD |
| >0x00000010</TD |
| ><TD |
| >The device supports the <A |
| HREF="x7013.htm" |
| >Raw |
| VBI Capture</A |
| > interface, providing Teletext and Closed Caption |
| data.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_VBI_OUTPUT</CODE |
| ></TD |
| ><TD |
| >0x00000020</TD |
| ><TD |
| >The device supports the <A |
| HREF="x7013.htm" |
| >Raw VBI Output</A |
| > interface.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_SLICED_VBI_CAPTURE</CODE |
| ></TD |
| ><TD |
| >0x00000040</TD |
| ><TD |
| >The device supports the <A |
| HREF="x7236.htm" |
| >Sliced VBI Capture</A |
| > interface.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_SLICED_VBI_OUTPUT</CODE |
| ></TD |
| ><TD |
| >0x00000080</TD |
| ><TD |
| >The device supports the <A |
| HREF="x7236.htm" |
| >Sliced VBI Output</A |
| > interface.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_RDS_CAPTURE</CODE |
| ></TD |
| ><TD |
| >0x00000100</TD |
| ><TD |
| >[to be defined]</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_VIDEO_OUTPUT_OVERLAY</CODE |
| ></TD |
| ><TD |
| >0x00000200</TD |
| ><TD |
| >The device supports the <A |
| HREF="x6909.htm" |
| >Video |
| Output Overlay</A |
| > (OSD) interface. Unlike the <I |
| CLASS="WORDASWORD" |
| >Video |
| Overlay</I |
| > interface, this is a secondary function of video |
| output devices and overlays an image onto an outgoing video signal. |
| When the driver sets this flag, it must clear the |
| <CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_VIDEO_OVERLAY</CODE |
| > flag and vice |
| versa.<A |
| NAME="AEN13265" |
| HREF="r13105.htm#FTN.AEN13265" |
| ><SPAN |
| CLASS="footnote" |
| >[a]</SPAN |
| ></A |
| ></TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_TUNER</CODE |
| ></TD |
| ><TD |
| >0x00010000</TD |
| ><TD |
| >The device has some sort of tuner or modulator to |
| receive or emit RF-modulated video signals. For more information about |
| tuner and modulator programming see |
| <A |
| HREF="x394.htm" |
| >Section 1.6</A |
| >.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_AUDIO</CODE |
| ></TD |
| ><TD |
| >0x00020000</TD |
| ><TD |
| >The device has audio inputs or outputs. It may or |
| may not support audio recording or playback, in PCM or compressed |
| formats. PCM audio support must be implemented as ALSA or OSS |
| interface. For more information on audio inputs and outputs see <A |
| HREF="x341.htm" |
| >Section 1.5</A |
| >.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_RADIO</CODE |
| ></TD |
| ><TD |
| >0x00040000</TD |
| ><TD |
| >This is a radio receiver.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_READWRITE</CODE |
| ></TD |
| ><TD |
| >0x01000000</TD |
| ><TD |
| >The device supports the <A |
| HREF="c5742.htm#RW" |
| >read()</A |
| > and/or <A |
| HREF="c5742.htm#RW" |
| >write()</A |
| > |
| I/O methods.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_ASYNCIO</CODE |
| ></TD |
| ><TD |
| >0x02000000</TD |
| ><TD |
| >The device supports the <A |
| HREF="x5950.htm" |
| >asynchronous</A |
| > I/O methods.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CAP_STREAMING</CODE |
| ></TD |
| ><TD |
| >0x04000000</TD |
| ><TD |
| >The device supports the <A |
| HREF="x5791.htm" |
| >streaming</A |
| > I/O method.</TD |
| ></TR |
| ></TBODY |
| ><TR |
| ><TD |
| COLSPAN="3" |
| >Notes:<BR><A |
| NAME="FTN.AEN13265" |
| >a. </A |
| >The struct <A |
| HREF="r10595.htm#V4L2-FRAMEBUFFER" |
| >v4l2_framebuffer</A |
| > lacks an |
| enum <A |
| HREF="x5953.htm#V4L2-BUF-TYPE" |
| >v4l2_buf_type</A |
| > field, therefore the type of overlay is implied by the |
| driver capabilities.<BR></TD |
| ></TR |
| ></TABLE |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN13305" |
| ></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 device is not compatible with this |
| specification.</P |
| ></DD |
| ></DL |
| ></DIV |
| ></DIV |
| ><DIV |
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