1<refentry id="vidioc-dbg-g-chip-ident">
2  <refmeta>
3    <refentrytitle>ioctl VIDIOC_DBG_G_CHIP_IDENT</refentrytitle>
4    &manvol;
5  </refmeta>
6
7  <refnamediv>
8    <refname>VIDIOC_DBG_G_CHIP_IDENT</refname>
9    <refpurpose>Identify the chips on a TV card</refpurpose>
10  </refnamediv>
11
12  <refsynopsisdiv>
13    <funcsynopsis>
14      <funcprototype>
15	<funcdef>int <function>ioctl</function></funcdef>
16	<paramdef>int <parameter>fd</parameter></paramdef>
17	<paramdef>int <parameter>request</parameter></paramdef>
18	<paramdef>struct v4l2_dbg_chip_ident
19*<parameter>argp</parameter></paramdef>
20      </funcprototype>
21    </funcsynopsis>
22  </refsynopsisdiv>
23
24  <refsect1>
25    <title>Arguments</title>
26
27    <variablelist>
28      <varlistentry>
29	<term><parameter>fd</parameter></term>
30	<listitem>
31	  <para>&fd;</para>
32	</listitem>
33      </varlistentry>
34      <varlistentry>
35	<term><parameter>request</parameter></term>
36	<listitem>
37	  <para>VIDIOC_DBG_G_CHIP_IDENT</para>
38	</listitem>
39      </varlistentry>
40      <varlistentry>
41	<term><parameter>argp</parameter></term>
42	<listitem>
43	  <para></para>
44	</listitem>
45      </varlistentry>
46    </variablelist>
47  </refsect1>
48
49  <refsect1>
50    <title>Description</title>
51
52    <note>
53      <title>Experimental</title>
54
55      <para>This is an <link
56linkend="experimental">experimental</link> interface and may change in
57the future.</para>
58    </note>
59
60    <para>For driver debugging purposes this ioctl allows test
61applications to query the driver about the chips present on the TV
62card. Regular applications must not use it. When you found a chip
63specific bug, please contact the linux-media mailing list (&v4l-ml;)
64so it can be fixed.</para>
65
66    <para>To query the driver applications must initialize the
67<structfield>match.type</structfield> and
68<structfield>match.addr</structfield> or <structfield>match.name</structfield>
69fields of a &v4l2-dbg-chip-ident;
70and call <constant>VIDIOC_DBG_G_CHIP_IDENT</constant> with a pointer to
71this structure. On success the driver stores information about the
72selected chip in the <structfield>ident</structfield> and
73<structfield>revision</structfield> fields. On failure the structure
74remains unchanged.</para>
75
76    <para>When <structfield>match.type</structfield> is
77<constant>V4L2_CHIP_MATCH_HOST</constant>,
78<structfield>match.addr</structfield> selects the nth non-&i2c; chip
79on the TV card. You can enumerate all chips by starting at zero and
80incrementing <structfield>match.addr</structfield> by one until
81<constant>VIDIOC_DBG_G_CHIP_IDENT</constant> fails with an &EINVAL;.
82The number zero always selects the host chip, &eg; the chip connected
83to the PCI or USB bus.</para>
84
85    <para>When <structfield>match.type</structfield> is
86<constant>V4L2_CHIP_MATCH_I2C_DRIVER</constant>,
87<structfield>match.name</structfield> contains the I2C driver name.
88For instance
89<constant>"saa7127"</constant> will match any chip
90supported by the saa7127 driver, regardless of its &i2c; bus address.
91When multiple chips supported by the same driver are present, the
92ioctl will return <constant>V4L2_IDENT_AMBIGUOUS</constant> in the
93<structfield>ident</structfield> field.</para>
94
95    <para>When <structfield>match.type</structfield> is
96<constant>V4L2_CHIP_MATCH_I2C_ADDR</constant>,
97<structfield>match.addr</structfield> selects a chip by its 7 bit
98&i2c; bus address.</para>
99
100    <para>When <structfield>match.type</structfield> is
101<constant>V4L2_CHIP_MATCH_AC97</constant>,
102<structfield>match.addr</structfield> selects the nth AC97 chip
103on the TV card. You can enumerate all chips by starting at zero and
104incrementing <structfield>match.addr</structfield> by one until
105<constant>VIDIOC_DBG_G_CHIP_IDENT</constant> fails with an &EINVAL;.</para>
106
107    <para>On success, the <structfield>ident</structfield> field will
108contain a chip ID from the Linux
109<filename>media/v4l2-chip-ident.h</filename> header file, and the
110<structfield>revision</structfield> field will contain a driver
111specific value, or zero if no particular revision is associated with
112this chip.</para>
113
114    <para>When the driver could not identify the selected chip,
115<structfield>ident</structfield> will contain
116<constant>V4L2_IDENT_UNKNOWN</constant>. When no chip matched
117the ioctl will succeed but the
118<structfield>ident</structfield> field will contain
119<constant>V4L2_IDENT_NONE</constant>. If multiple chips matched,
120<structfield>ident</structfield> will contain
121<constant>V4L2_IDENT_AMBIGUOUS</constant>. In all these cases the
122<structfield>revision</structfield> field remains unchanged.</para>
123
124    <para>This ioctl is optional, not all drivers may support it. It
125was introduced in Linux 2.6.21, but the API was changed to the
126one described here in 2.6.29.</para>
127
128    <para>We recommended the <application>v4l2-dbg</application>
129utility over calling this ioctl directly. It is available from the
130LinuxTV v4l-dvb repository; see <ulink
131url="http://linuxtv.org/repo/">http://linuxtv.org/repo/</ulink> for
132access instructions.</para>
133
134    <!-- Note for convenience vidioc-dbg-g-register.sgml
135	 contains a duplicate of this table. -->
136    <table pgwide="1" frame="none" id="ident-v4l2-dbg-match">
137      <title>struct <structname>v4l2_dbg_match</structname></title>
138      <tgroup cols="4">
139	&cs-ustr;
140	<tbody valign="top">
141	  <row>
142	    <entry>__u32</entry>
143	    <entry><structfield>type</structfield></entry>
144	    <entry>See <xref linkend="ident-chip-match-types" /> for a list of
145possible types.</entry>
146	  </row>
147	  <row>
148	    <entry>union</entry>
149	    <entry>(anonymous)</entry>
150	  </row>
151	  <row>
152	    <entry></entry>
153	    <entry>__u32</entry>
154	    <entry><structfield>addr</structfield></entry>
155	    <entry>Match a chip by this number, interpreted according
156to the <structfield>type</structfield> field.</entry>
157	  </row>
158	  <row>
159	    <entry></entry>
160	    <entry>char</entry>
161	    <entry><structfield>name[32]</structfield></entry>
162	    <entry>Match a chip by this name, interpreted according
163to the <structfield>type</structfield> field.</entry>
164	  </row>
165	</tbody>
166      </tgroup>
167    </table>
168
169    <table pgwide="1" frame="none" id="v4l2-dbg-chip-ident">
170      <title>struct <structname>v4l2_dbg_chip_ident</structname></title>
171      <tgroup cols="3">
172	&cs-str;
173	<tbody valign="top">
174	  <row>
175	    <entry>struct v4l2_dbg_match</entry>
176	    <entry><structfield>match</structfield></entry>
177	    <entry>How to match the chip, see <xref linkend="ident-v4l2-dbg-match" />.</entry>
178	  </row>
179	  <row>
180	    <entry>__u32</entry>
181	    <entry><structfield>ident</structfield></entry>
182	    <entry>A chip identifier as defined in the Linux
183<filename>media/v4l2-chip-ident.h</filename> header file, or one of
184the values from <xref linkend="chip-ids" />.</entry>
185	  </row>
186	  <row>
187	    <entry>__u32</entry>
188	    <entry><structfield>revision</structfield></entry>
189	    <entry>A chip revision, chip and driver specific.</entry>
190	  </row>
191	</tbody>
192      </tgroup>
193    </table>
194
195    <!-- Note for convenience vidioc-dbg-g-register.sgml
196	 contains a duplicate of this table. -->
197    <table pgwide="1" frame="none" id="ident-chip-match-types">
198      <title>Chip Match Types</title>
199      <tgroup cols="3">
200	&cs-def;
201	<tbody valign="top">
202	  <row>
203	    <entry><constant>V4L2_CHIP_MATCH_HOST</constant></entry>
204	    <entry>0</entry>
205	    <entry>Match the nth chip on the card, zero for the
206	    host chip. Does not match &i2c; chips.</entry>
207	  </row>
208	  <row>
209	    <entry><constant>V4L2_CHIP_MATCH_I2C_DRIVER</constant></entry>
210	    <entry>1</entry>
211	    <entry>Match an &i2c; chip by its driver name.</entry>
212	  </row>
213	  <row>
214	    <entry><constant>V4L2_CHIP_MATCH_I2C_ADDR</constant></entry>
215	    <entry>2</entry>
216	    <entry>Match a chip by its 7 bit &i2c; bus address.</entry>
217	  </row>
218	  <row>
219	    <entry><constant>V4L2_CHIP_MATCH_AC97</constant></entry>
220	    <entry>3</entry>
221	    <entry>Match the nth anciliary AC97 chip.</entry>
222	  </row>
223	</tbody>
224      </tgroup>
225    </table>
226
227    <!-- This is an anonymous enum in media/v4l2-chip-ident.h. -->
228    <table pgwide="1" frame="none" id="chip-ids">
229      <title>Chip Identifiers</title>
230      <tgroup cols="3">
231	&cs-def;
232	<tbody valign="top">
233	  <row>
234	    <entry><constant>V4L2_IDENT_NONE</constant></entry>
235	    <entry>0</entry>
236	    <entry>No chip matched.</entry>
237	  </row>
238	  <row>
239	    <entry><constant>V4L2_IDENT_AMBIGUOUS</constant></entry>
240	    <entry>1</entry>
241	    <entry>Multiple chips matched.</entry>
242	  </row>
243	  <row>
244	    <entry><constant>V4L2_IDENT_UNKNOWN</constant></entry>
245	    <entry>2</entry>
246	    <entry>A chip is present at this address, but the driver
247could not identify it.</entry>
248	  </row>
249	</tbody>
250      </tgroup>
251    </table>
252  </refsect1>
253
254  <refsect1>
255    &return-value;
256
257    <variablelist>
258      <varlistentry>
259	<term><errorcode>EINVAL</errorcode></term>
260	<listitem>
261	  <para>The <structfield>match_type</structfield> is invalid.</para>
262	</listitem>
263      </varlistentry>
264     </variablelist>
265  </refsect1>
266</refentry>
267