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[linux/fpc-iii.git] / Documentation / DocBook / v4l / vidioc-querycap.xml
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1 <refentry id="vidioc-querycap">
2   <refmeta>
3     <refentrytitle>ioctl VIDIOC_QUERYCAP</refentrytitle>
4     &manvol;
5   </refmeta>
7   <refnamediv>
8     <refname>VIDIOC_QUERYCAP</refname>
9     <refpurpose>Query device capabilities</refpurpose>
10   </refnamediv>
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_capability *<parameter>argp</parameter></paramdef>
19       </funcprototype>
20     </funcsynopsis>
21   </refsynopsisdiv>
23   <refsect1>
24     <title>Arguments</title>
26     <variablelist>
27       <varlistentry>
28         <term><parameter>fd</parameter></term>
29         <listitem>
30           <para>&fd;</para>
31         </listitem>
32       </varlistentry>
33       <varlistentry>
34         <term><parameter>request</parameter></term>
35         <listitem>
36           <para>VIDIOC_QUERYCAP</para>
37         </listitem>
38       </varlistentry>
39       <varlistentry>
40         <term><parameter>argp</parameter></term>
41         <listitem>
42           <para></para>
43         </listitem>
44       </varlistentry>
45     </variablelist>
46   </refsect1>
48   <refsect1>
49     <title>Description</title>
51     <para>All V4L2 devices support the
52 <constant>VIDIOC_QUERYCAP</constant> ioctl. It is used to identify
53 kernel devices compatible with this specification and to obtain
54 information about driver and hardware capabilities. The ioctl takes a
55 pointer to a &v4l2-capability; which is filled by the driver. When the
56 driver is not compatible with this specification the ioctl returns an
57 &EINVAL;.</para>
59     <table pgwide="1" frame="none" id="v4l2-capability">
60       <title>struct <structname>v4l2_capability</structname></title>
61       <tgroup cols="3">
62         &cs-str;
63         <tbody valign="top">
64           <row>
65             <entry>__u8</entry>
66             <entry><structfield>driver</structfield>[16]</entry>
67             <entry><para>Name of the driver, a unique NUL-terminated
68 ASCII string. For example: "bttv". Driver specific applications can
69 use this information to verify the driver identity. It is also useful
70 to work around known bugs, or to identify drivers in error reports.
71 The driver version is stored in the <structfield>version</structfield>
72 field.</para><para>Storing strings in fixed sized arrays is bad
73 practice but unavoidable here. Drivers and applications should take
74 precautions to never read or write beyond the end of the array and to
75 make sure the strings are properly NUL-terminated.</para></entry>
76           </row>
77           <row>
78             <entry>__u8</entry>
79             <entry><structfield>card</structfield>[32]</entry>
80             <entry>Name of the device, a NUL-terminated ASCII string.
81 For example: "Yoyodyne TV/FM". One driver may support different brands
82 or models of video hardware. This information is intended for users,
83 for example in a menu of available devices. Since multiple TV cards of
84 the same brand may be installed which are supported by the same
85 driver, this name should be combined with the character device file
86 name (&eg; <filename>/dev/video2</filename>) or the
87 <structfield>bus_info</structfield> string to avoid
88 ambiguities.</entry>
89           </row>
90           <row>
91             <entry>__u8</entry>
92             <entry><structfield>bus_info</structfield>[32]</entry>
93             <entry>Location of the device in the system, a
94 NUL-terminated ASCII string. For example: "PCI Slot 4". This
95 information is intended for users, to distinguish multiple
96 identical devices. If no such information is available the field may
97 simply count the devices controlled by the driver, or contain the
98 empty string (<structfield>bus_info</structfield>[0] = 0).<!-- XXX pci_dev->slot_name example --></entry>
99           </row>
100           <row>
101             <entry>__u32</entry>
102             <entry><structfield>version</structfield></entry>
103             <entry><para>Version number of the driver. Together with
104 the <structfield>driver</structfield> field this identifies a
105 particular driver. The version number is formatted using the
106 <constant>KERNEL_VERSION()</constant> macro:</para></entry>
107           </row>
108           <row>
109             <entry spanname="hspan"><para>
110 <programlisting>
111 #define KERNEL_VERSION(a,b,c) (((a) &lt;&lt; 16) + ((b) &lt;&lt; 8) + (c))
113 __u32 version = KERNEL_VERSION(0, 8, 1);
115 printf ("Version: %u.%u.%u\n",
116         (version &gt;&gt; 16) &amp; 0xFF,
117         (version &gt;&gt; 8) &amp; 0xFF,
118          version &amp; 0xFF);
119 </programlisting></para></entry>
120           </row>
121           <row>
122             <entry>__u32</entry>
123             <entry><structfield>capabilities</structfield></entry>
124             <entry>Device capabilities, see <xref
125                 linkend="device-capabilities" />.</entry>
126           </row>
127           <row>
128             <entry>__u32</entry>
129             <entry><structfield>reserved</structfield>[4]</entry>
130             <entry>Reserved for future extensions. Drivers must set
131 this array to zero.</entry>
132           </row>
133         </tbody>
134       </tgroup>
135     </table>
137     <table pgwide="1" frame="none" id="device-capabilities">
138       <title>Device Capabilities Flags</title>
139       <tgroup cols="3">
140         &cs-def;
141         <tbody valign="top">
142           <row>
143             <entry><constant>V4L2_CAP_VIDEO_CAPTURE</constant></entry>
144             <entry>0x00000001</entry>
145             <entry>The device supports the single-planar API through the <link
146 linkend="capture">Video Capture</link> interface.</entry>
147           </row>
148           <row>
149             <entry><constant>V4L2_CAP_VIDEO_CAPTURE_MPLANE</constant></entry>
150             <entry>0x00001000</entry>
151             <entry>The device supports the
152             <link linkend="planar-apis">multi-planar API</link> through the
153             <link linkend="capture">Video Capture</link> interface.</entry>
154           </row>
155           <row>
156             <entry><constant>V4L2_CAP_VIDEO_OUTPUT</constant></entry>
157             <entry>0x00000002</entry>
158             <entry>The device supports the single-planar API through the <link
159 linkend="output">Video Output</link> interface.</entry>
160           </row>
161           <row>
162             <entry><constant>V4L2_CAP_VIDEO_OUTPUT_MPLANE</constant></entry>
163             <entry>0x00002000</entry>
164             <entry>The device supports the
165             <link linkend="planar-apis">multi-planar API</link> through the
166             <link linkend="output">Video Output</link> interface.</entry>
167           </row>
168           <row>
169             <entry><constant>V4L2_CAP_VIDEO_OVERLAY</constant></entry>
170             <entry>0x00000004</entry>
171             <entry>The device supports the <link
172 linkend="overlay">Video Overlay</link> interface. A video overlay device
173 typically stores captured images directly in the video memory of a
174 graphics card, with hardware clipping and scaling.</entry>
175           </row>
176           <row>
177             <entry><constant>V4L2_CAP_VBI_CAPTURE</constant></entry>
178             <entry>0x00000010</entry>
179             <entry>The device supports the <link linkend="raw-vbi">Raw
180 VBI Capture</link> interface, providing Teletext and Closed Caption
181 data.</entry>
182           </row>
183           <row>
184             <entry><constant>V4L2_CAP_VBI_OUTPUT</constant></entry>
185             <entry>0x00000020</entry>
186             <entry>The device supports the <link linkend="raw-vbi">Raw VBI Output</link> interface.</entry>
187           </row>
188           <row>
189             <entry><constant>V4L2_CAP_SLICED_VBI_CAPTURE</constant></entry>
190             <entry>0x00000040</entry>
191             <entry>The device supports the <link linkend="sliced">Sliced VBI Capture</link> interface.</entry>
192           </row>
193           <row>
194             <entry><constant>V4L2_CAP_SLICED_VBI_OUTPUT</constant></entry>
195             <entry>0x00000080</entry>
196             <entry>The device supports the <link linkend="sliced">Sliced VBI Output</link> interface.</entry>
197           </row>
198           <row>
199             <entry><constant>V4L2_CAP_RDS_CAPTURE</constant></entry>
200             <entry>0x00000100</entry>
201             <entry>The device supports the <link linkend="rds">RDS</link> capture interface.</entry>
202           </row>
203           <row>
204             <entry><constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant></entry>
205             <entry>0x00000200</entry>
206             <entry>The device supports the <link linkend="osd">Video
207 Output Overlay</link> (OSD) interface. Unlike the <wordasword>Video
208 Overlay</wordasword> interface, this is a secondary function of video
209 output devices and overlays an image onto an outgoing video signal.
210 When the driver sets this flag, it must clear the
211 <constant>V4L2_CAP_VIDEO_OVERLAY</constant> flag and vice
212 versa.<footnote><para>The &v4l2-framebuffer; lacks an
213 &v4l2-buf-type; field, therefore the type of overlay is implied by the
214 driver capabilities.</para></footnote></entry>
215           </row>
216           <row>
217             <entry><constant>V4L2_CAP_HW_FREQ_SEEK</constant></entry>
218             <entry>0x00000400</entry>
219             <entry>The device supports the &VIDIOC-S-HW-FREQ-SEEK; ioctl for
220 hardware frequency seeking.</entry>
221           </row>
222           <row>
223             <entry><constant>V4L2_CAP_RDS_OUTPUT</constant></entry>
224             <entry>0x00000800</entry>
225             <entry>The device supports the <link linkend="rds">RDS</link> output interface.</entry>
226           </row>
227           <row>
228             <entry><constant>V4L2_CAP_TUNER</constant></entry>
229             <entry>0x00010000</entry>
230             <entry>The device has some sort of tuner to
231 receive RF-modulated video signals. For more information about
232 tuner programming see
233 <xref linkend="tuner" />.</entry>
234           </row>
235           <row>
236             <entry><constant>V4L2_CAP_AUDIO</constant></entry>
237             <entry>0x00020000</entry>
238             <entry>The device has audio inputs or outputs. It may or
239 may not support audio recording or playback, in PCM or compressed
240 formats. PCM audio support must be implemented as ALSA or OSS
241 interface. For more information on audio inputs and outputs see <xref
242                 linkend="audio" />.</entry>
243           </row>
244           <row>
245             <entry><constant>V4L2_CAP_RADIO</constant></entry>
246             <entry>0x00040000</entry>
247             <entry>This is a radio receiver.</entry>
248           </row>
249           <row>
250             <entry><constant>V4L2_CAP_MODULATOR</constant></entry>
251             <entry>0x00080000</entry>
252             <entry>The device has some sort of modulator to
253 emit RF-modulated video/audio signals. For more information about
254 modulator programming see
255 <xref linkend="tuner" />.</entry>
256           </row>
257           <row>
258             <entry><constant>V4L2_CAP_READWRITE</constant></entry>
259             <entry>0x01000000</entry>
260             <entry>The device supports the <link
261 linkend="rw">read()</link> and/or <link linkend="rw">write()</link>
262 I/O methods.</entry>
263           </row>
264           <row>
265             <entry><constant>V4L2_CAP_ASYNCIO</constant></entry>
266             <entry>0x02000000</entry>
267             <entry>The device supports the <link
268 linkend="async">asynchronous</link> I/O methods.</entry>
269           </row>
270           <row>
271             <entry><constant>V4L2_CAP_STREAMING</constant></entry>
272             <entry>0x04000000</entry>
273             <entry>The device supports the <link
274 linkend="mmap">streaming</link> I/O method.</entry>
275           </row>
276         </tbody>
277       </tgroup>
278     </table>
279   </refsect1>
281   <refsect1>
282     &return-value;
284     <variablelist>
285       <varlistentry>
286         <term><errorcode>EINVAL</errorcode></term>
287         <listitem>
288           <para>The device is not compatible with this
289 specification.</para>
290         </listitem>
291       </varlistentry>
292     </variablelist>
293   </refsect1>
294 </refentry>
296 <!--
297 Local Variables:
298 mode: sgml
299 sgml-parent-document: "v4l2.sgml"
300 indent-tabs-mode: nil
301 End: