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Based on kernel version 3.15.4. Page generated on 2014-07-07 09:02 EST.

1	<refentry id="vidioc-querycap">
2	  <refmeta>
3	    <refentrytitle>ioctl VIDIOC_QUERYCAP</refentrytitle>
4	    &manvol;
5	  </refmeta>
6	
7	  <refnamediv>
8	    <refname>VIDIOC_QUERYCAP</refname>
9	    <refpurpose>Query device capabilities</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_capability *<parameter>argp</parameter></paramdef>
19	      </funcprototype>
20	    </funcsynopsis>
21	  </refsynopsisdiv>
22	
23	  <refsect1>
24	    <title>Arguments</title>
25	
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>
47	
48	  <refsect1>
49	    <title>Description</title>
50	
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>
58	
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.</para>
71	<para>Storing strings in fixed sized arrays is bad
72	practice but unavoidable here. Drivers and applications should take
73	precautions to never read or write beyond the end of the array and to
74	make sure the strings are properly NUL-terminated.</para></entry>
75		  </row>
76		  <row>
77		    <entry>__u8</entry>
78		    <entry><structfield>card</structfield>[32]</entry>
79		    <entry>Name of the device, a NUL-terminated UTF-8 string.
80	For example: "Yoyodyne TV/FM". One driver may support different brands
81	or models of video hardware. This information is intended for users,
82	for example in a menu of available devices. Since multiple TV cards of
83	the same brand may be installed which are supported by the same
84	driver, this name should be combined with the character device file
85	name (&eg; <filename>/dev/video2</filename>) or the
86	<structfield>bus_info</structfield> string to avoid
87	ambiguities.</entry>
88		  </row>
89		  <row>
90		    <entry>__u8</entry>
91		    <entry><structfield>bus_info</structfield>[32]</entry>
92		    <entry>Location of the device in the system, a
93	NUL-terminated ASCII string. For example: "PCI:0000:05:06.0". This
94	information is intended for users, to distinguish multiple
95	identical devices. If no such information is available the field must
96	simply count the devices controlled by the driver ("platform:vivi-000").
97	The bus_info must start with "PCI:" for PCI boards, "PCIe:" for PCI Express boards,
98	"usb-" for USB devices, "I2C:" for i2c devices, "ISA:" for ISA devices,
99	"parport" for parallel port devices and "platform:" for platform devices.</entry>
100		  </row>
101		  <row>
102		    <entry>__u32</entry>
103		    <entry><structfield>version</structfield></entry>
104		    <entry><para>Version number of the driver.</para>
105	<para>Starting on kernel 3.1, the version reported is provided per
106	V4L2 subsystem, following the same Kernel numberation scheme. However, it
107	should not always return the same version as the kernel, if, for example,
108	an stable or distribution-modified kernel uses the V4L2 stack from a
109	newer kernel.</para>
110	<para>The version number is formatted using the
111	<constant>KERNEL_VERSION()</constant> macro:</para></entry>
112		  </row>
113		  <row>
114		    <entry spanname="hspan"><para>
115	<programlisting>
116	#define KERNEL_VERSION(a,b,c) (((a) &lt;&lt; 16) + ((b) &lt;&lt; 8) + (c))
117	
118	__u32 version = KERNEL_VERSION(0, 8, 1);
119	
120	printf ("Version: %u.%u.%u\n",
121		(version &gt;&gt; 16) &amp; 0xFF,
122		(version &gt;&gt; 8) &amp; 0xFF,
123		 version &amp; 0xFF);
124	</programlisting></para></entry>
125		  </row>
126		  <row>
127		    <entry>__u32</entry>
128		    <entry><structfield>capabilities</structfield></entry>
129		    <entry>Available capabilities of the physical device as a whole, see <xref
130			linkend="device-capabilities" />. The same physical device can export
131			multiple devices in /dev (e.g. /dev/videoX, /dev/vbiY and /dev/radioZ).
132			The <structfield>capabilities</structfield> field should contain a union
133			of all capabilities available around the several V4L2 devices exported
134			to userspace.
135			For all those devices the <structfield>capabilities</structfield> field
136			returns the same set of	capabilities. This allows applications to open
137			just one of the devices (typically the video device) and discover whether
138			video, vbi and/or radio are also supported.
139		    </entry>
140		  </row>
141		  <row>
142		    <entry>__u32</entry>
143		    <entry><structfield>device_caps</structfield></entry>
144		    <entry>Device capabilities of the opened device, see <xref
145			linkend="device-capabilities" />. Should contain the available capabilities
146			of that specific device node. So, for example, <structfield>device_caps</structfield>
147			of a radio device will only contain radio related capabilities and
148			no video or vbi capabilities. This field is only set if the <structfield>capabilities</structfield>
149			field contains the <constant>V4L2_CAP_DEVICE_CAPS</constant> capability.
150			Only the <structfield>capabilities</structfield> field can have the
151			<constant>V4L2_CAP_DEVICE_CAPS</constant> capability, <structfield>device_caps</structfield>
152			will never set <constant>V4L2_CAP_DEVICE_CAPS</constant>.
153		    </entry>
154		  </row>
155		  <row>
156		    <entry>__u32</entry>
157		    <entry><structfield>reserved</structfield>[3]</entry>
158		    <entry>Reserved for future extensions. Drivers must set
159	this array to zero.</entry>
160		  </row>
161		</tbody>
162	      </tgroup>
163	    </table>
164	
165	    <table pgwide="1" frame="none" id="device-capabilities">
166	      <title>Device Capabilities Flags</title>
167	      <tgroup cols="3">
168		&cs-def;
169		<tbody valign="top">
170		  <row>
171		    <entry><constant>V4L2_CAP_VIDEO_CAPTURE</constant></entry>
172		    <entry>0x00000001</entry>
173		    <entry>The device supports the single-planar API through the <link
174	linkend="capture">Video Capture</link> interface.</entry>
175		  </row>
176		  <row>
177		    <entry><constant>V4L2_CAP_VIDEO_CAPTURE_MPLANE</constant></entry>
178		    <entry>0x00001000</entry>
179		    <entry>The device supports the
180		    <link linkend="planar-apis">multi-planar API</link> through the
181		    <link linkend="capture">Video Capture</link> interface.</entry>
182		  </row>
183		  <row>
184		    <entry><constant>V4L2_CAP_VIDEO_OUTPUT</constant></entry>
185		    <entry>0x00000002</entry>
186		    <entry>The device supports the single-planar API through the <link
187	linkend="output">Video Output</link> interface.</entry>
188		  </row>
189		  <row>
190		    <entry><constant>V4L2_CAP_VIDEO_OUTPUT_MPLANE</constant></entry>
191		    <entry>0x00002000</entry>
192		    <entry>The device supports the
193		    <link linkend="planar-apis">multi-planar API</link> through the
194		    <link linkend="output">Video Output</link> interface.</entry>
195		  </row>
196		  <row>
197		    <entry><constant>V4L2_CAP_VIDEO_M2M</constant></entry>
198		    <entry>0x00004000</entry>
199		    <entry>The device supports the single-planar API through the
200		    Video Memory-To-Memory interface.</entry>
201		  </row>
202		  <row>
203		    <entry><constant>V4L2_CAP_VIDEO_M2M_MPLANE</constant></entry>
204		    <entry>0x00008000</entry>
205		    <entry>The device supports the
206		    <link linkend="planar-apis">multi-planar API</link> through the
207		    Video Memory-To-Memory  interface.</entry>
208		  </row>
209		  <row>
210		    <entry><constant>V4L2_CAP_VIDEO_OVERLAY</constant></entry>
211		    <entry>0x00000004</entry>
212		    <entry>The device supports the <link
213	linkend="overlay">Video Overlay</link> interface. A video overlay device
214	typically stores captured images directly in the video memory of a
215	graphics card, with hardware clipping and scaling.</entry>
216		  </row>
217		  <row>
218		    <entry><constant>V4L2_CAP_VBI_CAPTURE</constant></entry>
219		    <entry>0x00000010</entry>
220		    <entry>The device supports the <link linkend="raw-vbi">Raw
221	VBI Capture</link> interface, providing Teletext and Closed Caption
222	data.</entry>
223		  </row>
224		  <row>
225		    <entry><constant>V4L2_CAP_VBI_OUTPUT</constant></entry>
226		    <entry>0x00000020</entry>
227		    <entry>The device supports the <link linkend="raw-vbi">Raw VBI Output</link> interface.</entry>
228		  </row>
229		  <row>
230		    <entry><constant>V4L2_CAP_SLICED_VBI_CAPTURE</constant></entry>
231		    <entry>0x00000040</entry>
232		    <entry>The device supports the <link linkend="sliced">Sliced VBI Capture</link> interface.</entry>
233		  </row>
234		  <row>
235		    <entry><constant>V4L2_CAP_SLICED_VBI_OUTPUT</constant></entry>
236		    <entry>0x00000080</entry>
237		    <entry>The device supports the <link linkend="sliced">Sliced VBI Output</link> interface.</entry>
238		  </row>
239		  <row>
240		    <entry><constant>V4L2_CAP_RDS_CAPTURE</constant></entry>
241		    <entry>0x00000100</entry>
242		    <entry>The device supports the <link linkend="rds">RDS</link> capture interface.</entry>
243		  </row>
244		  <row>
245		    <entry><constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant></entry>
246		    <entry>0x00000200</entry>
247		    <entry>The device supports the <link linkend="osd">Video
248	Output Overlay</link> (OSD) interface. Unlike the <wordasword>Video
249	Overlay</wordasword> interface, this is a secondary function of video
250	output devices and overlays an image onto an outgoing video signal.
251	When the driver sets this flag, it must clear the
252	<constant>V4L2_CAP_VIDEO_OVERLAY</constant> flag and vice
253	versa.<footnote><para>The &v4l2-framebuffer; lacks an
254	&v4l2-buf-type; field, therefore the type of overlay is implied by the
255	driver capabilities.</para></footnote></entry>
256		  </row>
257		  <row>
258		    <entry><constant>V4L2_CAP_HW_FREQ_SEEK</constant></entry>
259		    <entry>0x00000400</entry>
260		    <entry>The device supports the &VIDIOC-S-HW-FREQ-SEEK; ioctl for
261	hardware frequency seeking.</entry>
262		  </row>
263		  <row>
264		    <entry><constant>V4L2_CAP_RDS_OUTPUT</constant></entry>
265		    <entry>0x00000800</entry>
266		    <entry>The device supports the <link linkend="rds">RDS</link> output interface.</entry>
267		  </row>
268		  <row>
269		    <entry><constant>V4L2_CAP_TUNER</constant></entry>
270		    <entry>0x00010000</entry>
271		    <entry>The device has some sort of tuner to
272	receive RF-modulated video signals. For more information about
273	tuner programming see
274	<xref linkend="tuner" />.</entry>
275		  </row>
276		  <row>
277		    <entry><constant>V4L2_CAP_AUDIO</constant></entry>
278		    <entry>0x00020000</entry>
279		    <entry>The device has audio inputs or outputs. It may or
280	may not support audio recording or playback, in PCM or compressed
281	formats. PCM audio support must be implemented as ALSA or OSS
282	interface. For more information on audio inputs and outputs see <xref
283			linkend="audio" />.</entry>
284		  </row>
285		  <row>
286		    <entry><constant>V4L2_CAP_RADIO</constant></entry>
287		    <entry>0x00040000</entry>
288		    <entry>This is a radio receiver.</entry>
289		  </row>
290		  <row>
291		    <entry><constant>V4L2_CAP_MODULATOR</constant></entry>
292		    <entry>0x00080000</entry>
293		    <entry>The device has some sort of modulator to
294	emit RF-modulated video/audio signals. For more information about
295	modulator programming see
296	<xref linkend="tuner" />.</entry>
297		  </row>
298		  <row>
299		    <entry><constant>V4L2_CAP_SDR_CAPTURE</constant></entry>
300		    <entry>0x00100000</entry>
301		    <entry>The device supports the
302	<link linkend="sdr">SDR Capture</link> interface.</entry>
303		  </row>
304		  <row>
305		    <entry><constant>V4L2_CAP_READWRITE</constant></entry>
306		    <entry>0x01000000</entry>
307		    <entry>The device supports the <link
308	linkend="rw">read()</link> and/or <link linkend="rw">write()</link>
309	I/O methods.</entry>
310		  </row>
311		  <row>
312		    <entry><constant>V4L2_CAP_ASYNCIO</constant></entry>
313		    <entry>0x02000000</entry>
314		    <entry>The device supports the <link
315	linkend="async">asynchronous</link> I/O methods.</entry>
316		  </row>
317		  <row>
318		    <entry><constant>V4L2_CAP_STREAMING</constant></entry>
319		    <entry>0x04000000</entry>
320		    <entry>The device supports the <link
321	linkend="mmap">streaming</link> I/O method.</entry>
322		  </row>
323		  <row>
324		    <entry><constant>V4L2_CAP_DEVICE_CAPS</constant></entry>
325		    <entry>0x80000000</entry>
326		    <entry>The driver fills the <structfield>device_caps</structfield>
327		    field. This capability can only appear in the <structfield>capabilities</structfield>
328		    field and never in the <structfield>device_caps</structfield> field.</entry>
329		  </row>
330		</tbody>
331	      </tgroup>
332	    </table>
333	  </refsect1>
334	
335	  <refsect1>
336	    &return-value;
337	  </refsect1>
338	</refentry>
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