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| >Video for Linux Two API Specification: Revision 0.24</TH |
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| >V4L2 open()</H1 |
| ><DIV |
| CLASS="REFNAMEDIV" |
| ><A |
| NAME="AEN14094" |
| ></A |
| ><H2 |
| >Name</H2 |
| >v4l2-open -- Open a V4L2 device</DIV |
| ><DIV |
| CLASS="REFSYNOPSISDIV" |
| ><A |
| NAME="AEN14097" |
| ></A |
| ><H2 |
| >Synopsis</H2 |
| ><DIV |
| CLASS="FUNCSYNOPSIS" |
| ><P |
| ></P |
| ><A |
| NAME="AEN14098" |
| ></A |
| ><PRE |
| CLASS="FUNCSYNOPSISINFO" |
| >#include <fcntl.h></PRE |
| ><P |
| ><CODE |
| ><CODE |
| CLASS="FUNCDEF" |
| >int open</CODE |
| >(const char *device_name, int flags);</CODE |
| ></P |
| ><P |
| ></P |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN14107" |
| ></A |
| ><H2 |
| >Arguments</H2 |
| ><P |
| ></P |
| ><DIV |
| CLASS="VARIABLELIST" |
| ><DL |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >device_name</CODE |
| ></DT |
| ><DD |
| ><P |
| >Device to be opened.</P |
| ></DD |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >flags</CODE |
| ></DT |
| ><DD |
| ><P |
| >Open flags. Access mode must be |
| <CODE |
| CLASS="CONSTANT" |
| >O_RDWR</CODE |
| >. This is just a technicality, input devices |
| still support only reading and output devices only writing.</P |
| ><P |
| >When the <CODE |
| CLASS="CONSTANT" |
| >O_NONBLOCK</CODE |
| > flag is |
| given, the read() function and the <A |
| HREF="r12878.htm" |
| ><CODE |
| CLASS="CONSTANT" |
| >VIDIOC_DQBUF</CODE |
| ></A |
| > ioctl will return |
| the <SPAN |
| CLASS="ERRORCODE" |
| >EAGAIN</SPAN |
| > error code when no data is available or no buffer is in the driver |
| outgoing queue, otherwise these functions block until data becomes |
| available. All V4L2 drivers exchanging data with applications must |
| support the <CODE |
| CLASS="CONSTANT" |
| >O_NONBLOCK</CODE |
| > flag.</P |
| ><P |
| >Other flags have no effect.</P |
| ></DD |
| ></DL |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN14128" |
| ></A |
| ><H2 |
| >Description</H2 |
| ><P |
| >To open a V4L2 device applications call |
| <CODE |
| CLASS="FUNCTION" |
| >open()</CODE |
| > with the desired device name. This |
| function has no side effects; all data format parameters, current |
| input or output, control values or other properties remain unchanged. |
| At the first <CODE |
| CLASS="FUNCTION" |
| >open()</CODE |
| > call after loading the driver |
| they will be reset to default values, drivers are never in an |
| undefined state.</P |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN14133" |
| ></A |
| ><H2 |
| >Return Value</H2 |
| ><P |
| >On success <CODE |
| CLASS="FUNCTION" |
| >open</CODE |
| > returns the new file |
| descriptor. On error -1 is returned, and the <CODE |
| CLASS="VARNAME" |
| >errno</CODE |
| > |
| variable is set appropriately. Possible error codes are:</P |
| ><P |
| ></P |
| ><DIV |
| CLASS="VARIABLELIST" |
| ><DL |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >EACCES</SPAN |
| ></DT |
| ><DD |
| ><P |
| >The caller has no permission to access the |
| device.</P |
| ></DD |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >EBUSY</SPAN |
| ></DT |
| ><DD |
| ><P |
| >The driver does not support multiple opens and the |
| device is already in use.</P |
| ></DD |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >ENXIO</SPAN |
| ></DT |
| ><DD |
| ><P |
| >No device corresponding to this device special file |
| exists.</P |
| ></DD |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >ENOMEM</SPAN |
| ></DT |
| ><DD |
| ><P |
| >Not enough kernel memory was available to complete the |
| request.</P |
| ></DD |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >EMFILE</SPAN |
| ></DT |
| ><DD |
| ><P |
| >The process already has the maximum number of |
| files open.</P |
| ></DD |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >ENFILE</SPAN |
| ></DT |
| ><DD |
| ><P |
| >The limit on the total number of files open on the |
| system has been reached.</P |
| ></DD |
| ></DL |
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