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>ioctl VIDIOC_G_CHIP_IDENT</TITLE
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><H1
><A
NAME="VIDIOC-G-CHIP-IDENT"
></A
>ioctl VIDIOC_G_CHIP_IDENT</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN9808"
></A
><H2
>Name</H2
>VIDIOC_G_CHIP_IDENT&nbsp;--&nbsp;Identify the chips on a TV card</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN9811"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><P
></P
><A
NAME="AEN9812"
></A
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int ioctl</CODE
>(int fd, int request, struct v4l2_chip_ident
*argp);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN9822"
></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_G_CHIP_IDENT</P
></DD
><DT
><CODE
CLASS="PARAMETER"
>argp</CODE
></DT
><DD
><P
></P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN9842"
></A
><H2
>Description</H2
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Experimental: </B
>This is an <A
HREF="x16453.htm"
>experimental</A
> interface and may change in
the future.</P
></BLOCKQUOTE
></DIV
><P
>For driver debugging purposes this ioctl allows test
applications to query the driver about the chips present on the TV
card. Regular applications should not use it. When you found a chip
specific bug, please contact the Video4Linux mailing list (<A
HREF="https://listman.redhat.com/mailman/listinfo/video4linux-list"
TARGET="_top"
>https://listman.redhat.com/mailman/listinfo/video4linux-list</A
>)
so it can be fixed.</P
><P
>To query the driver applications must initialize the
<CODE
CLASS="STRUCTFIELD"
>match_type</CODE
> and
<CODE
CLASS="STRUCTFIELD"
>match_chip</CODE
> fields of a struct&nbsp;<A
HREF="r9804.htm#V4L2-CHIP-IDENT"
>v4l2_chip_ident</A
>
and call <CODE
CLASS="CONSTANT"
>VIDIOC_G_CHIP_IDENT</CODE
> with a pointer to
this structure. On success the driver stores information about the
selected chip in the <CODE
CLASS="STRUCTFIELD"
>ident</CODE
> and
<CODE
CLASS="STRUCTFIELD"
>revision</CODE
> fields. On failure the structure
remains unchanged.</P
><P
>When <CODE
CLASS="STRUCTFIELD"
>match_type</CODE
> is
<CODE
CLASS="CONSTANT"
>V4L2_CHIP_MATCH_HOST</CODE
>,
<CODE
CLASS="STRUCTFIELD"
>match_chip</CODE
> selects the nth non-I<SUP
>2</SUP
>C chip
on the TV card. You can enumerate all chips by starting at zero and
incrementing <CODE
CLASS="STRUCTFIELD"
>match_chip</CODE
> by one until
<CODE
CLASS="CONSTANT"
>VIDIOC_G_CHIP_IDENT</CODE
> fails with an <SPAN
CLASS="ERRORCODE"
>EINVAL</SPAN
> error code.
Drivers may also interpret <CODE
CLASS="STRUCTFIELD"
>match_chip</CODE
> as a
random ID, but we recommend against that. The number zero always
selects the host chip, e.&nbsp;g. the chip connected to the PCI bus.</P
><P
>When <CODE
CLASS="STRUCTFIELD"
>match_type</CODE
> is
<CODE
CLASS="CONSTANT"
>V4L2_CHIP_MATCH_I2C_DRIVER</CODE
>,
<CODE
CLASS="STRUCTFIELD"
>match_chip</CODE
> contains a driver ID as defined
in the <TT
CLASS="FILENAME"
>linux/i2c-id.h</TT
> header file. For instance
<CODE
CLASS="CONSTANT"
>I2C_DRIVERID_SAA7127</CODE
> will match any chip
supported by the saa7127 driver, regardless of its I<SUP
>2</SUP
>C bus address.
When multiple chips supported by the same driver are present, the
ioctl will return <CODE
CLASS="CONSTANT"
>V4L2_IDENT_AMBIGUOUS</CODE
> in the
<CODE
CLASS="STRUCTFIELD"
>ident</CODE
> field.</P
><P
>When <CODE
CLASS="STRUCTFIELD"
>match_type</CODE
> is
<CODE
CLASS="CONSTANT"
>V4L2_CHIP_MATCH_I2C_ADDR</CODE
>,
<CODE
CLASS="STRUCTFIELD"
>match_chip</CODE
> selects a chip by its 7 bit
I<SUP
>2</SUP
>C bus address.</P
><P
>On success, the <CODE
CLASS="STRUCTFIELD"
>ident</CODE
> field will
contain a chip ID from the Linux
<TT
CLASS="FILENAME"
>media/v4l2-chip-ident.h</TT
> header file, and the
<CODE
CLASS="STRUCTFIELD"
>revision</CODE
> field will contain a driver
specific value, or zero if no particular revision is associated with
this chip.</P
><P
>When the driver could not identify the selected chip,
<CODE
CLASS="STRUCTFIELD"
>ident</CODE
> will contain
<CODE
CLASS="CONSTANT"
>V4L2_IDENT_UNKNOWN</CODE
>. When no chip matched
<CODE
CLASS="STRUCTFIELD"
>match_type</CODE
> and
<CODE
CLASS="STRUCTFIELD"
>match_chip</CODE
>, the ioctl will succeed but the
<CODE
CLASS="STRUCTFIELD"
>ident</CODE
> field will contain
<CODE
CLASS="CONSTANT"
>V4L2_IDENT_NONE</CODE
>. If multiple chips matched,
<CODE
CLASS="STRUCTFIELD"
>ident</CODE
> will contain
<CODE
CLASS="CONSTANT"
>V4L2_IDENT_AMBIGUOUS</CODE
>. In all these cases the
<CODE
CLASS="STRUCTFIELD"
>revision</CODE
> field remains unchanged.</P
><P
>This ioctl is optional, not all drivers may support it. It
was introduced in Linux 2.6.21.</P
><P
>We recommended the <SPAN
CLASS="APPLICATION"
>v4l2-dbg</SPAN
>
utility over calling this ioctl directly. It is available from the
LinuxTV v4l-dvb repository; see <A
HREF="http://linuxtv.org/repo/"
TARGET="_top"
>http://linuxtv.org/repo/</A
> for
access instructions.</P
><DIV
CLASS="TABLE"
><A
NAME="V4L2-CHIP-IDENT"
></A
><P
><B
>Table 1. struct <CODE
CLASS="STRUCTNAME"
>v4l2_chip_ident</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"
>match_type</CODE
></TD
><TD
>See <A
HREF="r9804.htm#IDENT-CHIP-MATCH-TYPES"
>Table 2</A
> for a list of
possible types.</TD
></TR
><TR
><TD
>__u32</TD
><TD
><CODE
CLASS="STRUCTFIELD"
>match_chip</CODE
></TD
><TD
>Match a chip by this number, interpreted according
to the <CODE
CLASS="STRUCTFIELD"
>match_type</CODE
> field.</TD
></TR
><TR
><TD
>__u32</TD
><TD
><CODE
CLASS="STRUCTFIELD"
>ident</CODE
></TD
><TD
>A chip identifier as defined in the Linux
<TT
CLASS="FILENAME"
>media/v4l2-chip-ident.h</TT
> header file, or one of
the values from <A
HREF="r9804.htm#CHIP-IDS"
>Table 3</A
>.</TD
></TR
><TR
><TD
>__u32</TD
><TD
><CODE
CLASS="STRUCTFIELD"
>revision</CODE
></TD
><TD
>A chip revision, chip and driver specific.</TD
></TR
></TBODY
></TABLE
></DIV
><DIV
CLASS="TABLE"
><A
NAME="IDENT-CHIP-MATCH-TYPES"
></A
><P
><B
>Table 2. Chip Match Types</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_CHIP_MATCH_HOST</CODE
></TD
><TD
>0</TD
><TD
>Match the nth chip on the card, zero for the
            host chip. Does not match I<SUP
>2</SUP
>C chips.</TD
></TR
><TR
><TD
><CODE
CLASS="CONSTANT"
>V4L2_CHIP_MATCH_I2C_DRIVER</CODE
></TD
><TD
>1</TD
><TD
>Match an I<SUP
>2</SUP
>C chip by its driver ID from the
<TT
CLASS="FILENAME"
>linux/i2c-id.h</TT
> header file.</TD
></TR
><TR
><TD
><CODE
CLASS="CONSTANT"
>V4L2_CHIP_MATCH_I2C_ADDR</CODE
></TD
><TD
>2</TD
><TD
>Match a chip by its 7 bit I<SUP
>2</SUP
>C bus address.</TD
></TR
></TBODY
></TABLE
></DIV
><DIV
CLASS="TABLE"
><A
NAME="CHIP-IDS"
></A
><P
><B
>Table 3. Chip Identifiers</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_IDENT_NONE</CODE
></TD
><TD
>0</TD
><TD
>No chip matched.</TD
></TR
><TR
><TD
><CODE
CLASS="CONSTANT"
>V4L2_IDENT_AMBIGUOUS</CODE
></TD
><TD
>1</TD
><TD
>Multiple chips matched.</TD
></TR
><TR
><TD
><CODE
CLASS="CONSTANT"
>V4L2_IDENT_UNKNOWN</CODE
></TD
><TD
>2</TD
><TD
>A chip is present at this address, but the driver
could not identify it.</TD
></TR
></TBODY
></TABLE
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN9981"
></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 driver does not support this ioctl, or the
<CODE
CLASS="STRUCTFIELD"
>match_type</CODE
> is invalid.</P
></DD
></DL
></DIV
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