1 .. SPDX-License-Identifier: GFDL-1.1-no-invari 1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L 2 .. c:namespace:: V4L
3 3
4 .. _VIDIOC_QUERYCAP: 4 .. _VIDIOC_QUERYCAP:
5 5
6 ********************* 6 *********************
7 ioctl VIDIOC_QUERYCAP 7 ioctl VIDIOC_QUERYCAP
8 ********************* 8 *********************
9 9
10 Name 10 Name
11 ==== 11 ====
12 12
13 VIDIOC_QUERYCAP - Query device capabilities 13 VIDIOC_QUERYCAP - Query device capabilities
14 14
15 Synopsis 15 Synopsis
16 ======== 16 ========
17 17
18 .. c:macro:: VIDIOC_QUERYCAP 18 .. c:macro:: VIDIOC_QUERYCAP
19 19
20 ``int ioctl(int fd, VIDIOC_QUERYCAP, struct v4 20 ``int ioctl(int fd, VIDIOC_QUERYCAP, struct v4l2_capability *argp)``
21 21
22 Arguments 22 Arguments
23 ========= 23 =========
24 24
25 ``fd`` 25 ``fd``
26 File descriptor returned by :c:func:`open( 26 File descriptor returned by :c:func:`open()`.
27 27
28 ``argp`` 28 ``argp``
29 Pointer to struct :c:type:`v4l2_capability 29 Pointer to struct :c:type:`v4l2_capability`.
30 30
31 Description 31 Description
32 =========== 32 ===========
33 33
34 All V4L2 devices support the ``VIDIOC_QUERYCAP 34 All V4L2 devices support the ``VIDIOC_QUERYCAP`` ioctl. It is used to
35 identify kernel devices compatible with this s 35 identify kernel devices compatible with this specification and to obtain
36 information about driver and hardware capabili 36 information about driver and hardware capabilities. The ioctl takes a
37 pointer to a struct :c:type:`v4l2_capability` 37 pointer to a struct :c:type:`v4l2_capability` which is
38 filled by the driver. When the driver is not c 38 filled by the driver. When the driver is not compatible with this
39 specification the ioctl returns an ``EINVAL`` 39 specification the ioctl returns an ``EINVAL`` error code.
40 40
41 .. c:type:: v4l2_capability 41 .. c:type:: v4l2_capability
42 42
43 .. tabularcolumns:: |p{1.4cm}|p{2.8cm}|p{13.1c 43 .. tabularcolumns:: |p{1.4cm}|p{2.8cm}|p{13.1cm}|
44 44
45 .. cssclass:: longtable 45 .. cssclass:: longtable
46 46
47 .. flat-table:: struct v4l2_capability 47 .. flat-table:: struct v4l2_capability
48 :header-rows: 0 48 :header-rows: 0
49 :stub-columns: 0 49 :stub-columns: 0
50 :widths: 3 4 20 50 :widths: 3 4 20
51 51
52 * - __u8 52 * - __u8
53 - ``driver``\ [16] 53 - ``driver``\ [16]
54 - Name of the driver, a unique NUL-termi 54 - Name of the driver, a unique NUL-terminated ASCII string. For
55 example: "bttv". Driver specific appli 55 example: "bttv". Driver specific applications can use this
56 information to verify the driver ident 56 information to verify the driver identity. It is also useful to
57 work around known bugs, or to identify 57 work around known bugs, or to identify drivers in error reports.
58 58
59 Storing strings in fixed sized arrays 59 Storing strings in fixed sized arrays is bad practice but
60 unavoidable here. Drivers and applicat 60 unavoidable here. Drivers and applications should take precautions
61 to never read or write beyond the end 61 to never read or write beyond the end of the array and to make
62 sure the strings are properly NUL-term 62 sure the strings are properly NUL-terminated.
63 * - __u8 63 * - __u8
64 - ``card``\ [32] 64 - ``card``\ [32]
65 - Name of the device, a NUL-terminated U 65 - Name of the device, a NUL-terminated UTF-8 string. For example:
66 "Yoyodyne TV/FM". One driver may suppo 66 "Yoyodyne TV/FM". One driver may support different brands or
67 models of video hardware. This informa 67 models of video hardware. This information is intended for users,
68 for example in a menu of available dev 68 for example in a menu of available devices. Since multiple TV
69 cards of the same brand may be install 69 cards of the same brand may be installed which are supported by
70 the same driver, this name should be c 70 the same driver, this name should be combined with the character
71 device file name (e. g. ``/dev/video2` 71 device file name (e. g. ``/dev/video2``) or the ``bus_info``
72 string to avoid ambiguities. 72 string to avoid ambiguities.
73 * - __u8 73 * - __u8
74 - ``bus_info``\ [32] 74 - ``bus_info``\ [32]
75 - Location of the device in the system, 75 - Location of the device in the system, a NUL-terminated ASCII
76 string. For example: "PCI:0000:05:06.0 76 string. For example: "PCI:0000:05:06.0". This information is
77 intended for users, to distinguish mul 77 intended for users, to distinguish multiple identical devices. If
78 no such information is available the f 78 no such information is available the field must simply count the
79 devices controlled by the driver ("pla 79 devices controlled by the driver ("platform:vivid-000"). The
80 bus_info must start with "PCI:" for PC 80 bus_info must start with "PCI:" for PCI boards, "PCIe:" for PCI
81 Express boards, "usb-" for USB devices 81 Express boards, "usb-" for USB devices, "I2C:" for i2c devices,
82 "ISA:" for ISA devices, "parport" for 82 "ISA:" for ISA devices, "parport" for parallel port devices and
83 "platform:" for platform devices. 83 "platform:" for platform devices.
84 * - __u32 84 * - __u32
85 - ``version`` 85 - ``version``
86 - Version number of the driver. 86 - Version number of the driver.
87 87
88 Starting with kernel 3.1, the version 88 Starting with kernel 3.1, the version reported is provided by the
89 V4L2 subsystem following the kernel nu 89 V4L2 subsystem following the kernel numbering scheme. However, it
90 may not always return the same version 90 may not always return the same version as the kernel if, for
91 example, a stable or distribution-modi 91 example, a stable or distribution-modified kernel uses the V4L2
92 stack from a newer kernel. 92 stack from a newer kernel.
93 93
94 The version number is formatted using 94 The version number is formatted using the ``KERNEL_VERSION()``
95 macro. For example if the media stack 95 macro. For example if the media stack corresponds to the V4L2
96 version shipped with Kernel 4.14, it w 96 version shipped with Kernel 4.14, it would be equivalent to:
97 * - :cspan:`2` 97 * - :cspan:`2`
98 98
99 ``#define KERNEL_VERSION(a,b,c) (((a) 99 ``#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))``
100 100
101 ``__u32 version = KERNEL_VERSION(4, 14 101 ``__u32 version = KERNEL_VERSION(4, 14, 0);``
102 102
103 ``printf ("Version: %u.%u.%u\\n",`` 103 ``printf ("Version: %u.%u.%u\\n",``
104 104
105 ``(version >> 16) & 0xFF, (version >> 105 ``(version >> 16) & 0xFF, (version >> 8) & 0xFF, version & 0xFF);``
106 * - __u32 106 * - __u32
107 - ``capabilities`` 107 - ``capabilities``
108 - Available capabilities of the physical 108 - Available capabilities of the physical device as a whole, see
109 :ref:`device-capabilities`. The same p 109 :ref:`device-capabilities`. The same physical device can export
110 multiple devices in /dev (e.g. /dev/vi 110 multiple devices in /dev (e.g. /dev/videoX, /dev/vbiY and
111 /dev/radioZ). The ``capabilities`` fie 111 /dev/radioZ). The ``capabilities`` field should contain a union of
112 all capabilities available around the 112 all capabilities available around the several V4L2 devices
113 exported to userspace. For all those d 113 exported to userspace. For all those devices the ``capabilities``
114 field returns the same set of capabili 114 field returns the same set of capabilities. This allows
115 applications to open just one of the d 115 applications to open just one of the devices (typically the video
116 device) and discover whether video, vb 116 device) and discover whether video, vbi and/or radio are also
117 supported. 117 supported.
118 * - __u32 118 * - __u32
119 - ``device_caps`` 119 - ``device_caps``
120 - Device capabilities of the opened devi 120 - Device capabilities of the opened device, see
121 :ref:`device-capabilities`. Should con 121 :ref:`device-capabilities`. Should contain the available
122 capabilities of that specific device n 122 capabilities of that specific device node. So, for example,
123 ``device_caps`` of a radio device will 123 ``device_caps`` of a radio device will only contain radio related
124 capabilities and no video or vbi capab 124 capabilities and no video or vbi capabilities. This field is only
125 set if the ``capabilities`` field cont 125 set if the ``capabilities`` field contains the
126 ``V4L2_CAP_DEVICE_CAPS`` capability. O 126 ``V4L2_CAP_DEVICE_CAPS`` capability. Only the ``capabilities``
127 field can have the ``V4L2_CAP_DEVICE_C 127 field can have the ``V4L2_CAP_DEVICE_CAPS`` capability,
128 ``device_caps`` will never set ``V4L2_ 128 ``device_caps`` will never set ``V4L2_CAP_DEVICE_CAPS``.
129 * - __u32 129 * - __u32
130 - ``reserved``\ [3] 130 - ``reserved``\ [3]
131 - Reserved for future extensions. Driver 131 - Reserved for future extensions. Drivers must set this array to
132 zero. 132 zero.
133 133
134 134
135 .. tabularcolumns:: |p{7.0cm}|p{2.6cm}|p{7.7cm 135 .. tabularcolumns:: |p{7.0cm}|p{2.6cm}|p{7.7cm}|
136 136
137 .. _device-capabilities: 137 .. _device-capabilities:
138 138
139 .. cssclass:: longtable 139 .. cssclass:: longtable
140 140
141 .. flat-table:: Device Capabilities Flags 141 .. flat-table:: Device Capabilities Flags
142 :header-rows: 0 142 :header-rows: 0
143 :stub-columns: 0 143 :stub-columns: 0
144 :widths: 3 1 4 144 :widths: 3 1 4
145 145
146 * - ``V4L2_CAP_VIDEO_CAPTURE`` 146 * - ``V4L2_CAP_VIDEO_CAPTURE``
147 - 0x00000001 147 - 0x00000001
148 - The device supports the single-planar 148 - The device supports the single-planar API through the
149 :ref:`Video Capture <capture>` interfa 149 :ref:`Video Capture <capture>` interface.
150 * - ``V4L2_CAP_VIDEO_CAPTURE_MPLANE`` 150 * - ``V4L2_CAP_VIDEO_CAPTURE_MPLANE``
151 - 0x00001000 151 - 0x00001000
152 - The device supports the :ref:`multi-pl 152 - The device supports the :ref:`multi-planar API <planar-apis>`
153 through the :ref:`Video Capture <captu 153 through the :ref:`Video Capture <capture>` interface.
154 * - ``V4L2_CAP_VIDEO_OUTPUT`` 154 * - ``V4L2_CAP_VIDEO_OUTPUT``
155 - 0x00000002 155 - 0x00000002
156 - The device supports the single-planar 156 - The device supports the single-planar API through the
157 :ref:`Video Output <output>` interface 157 :ref:`Video Output <output>` interface.
158 * - ``V4L2_CAP_VIDEO_OUTPUT_MPLANE`` 158 * - ``V4L2_CAP_VIDEO_OUTPUT_MPLANE``
159 - 0x00002000 159 - 0x00002000
160 - The device supports the :ref:`multi-pl 160 - The device supports the :ref:`multi-planar API <planar-apis>`
161 through the :ref:`Video Output <output 161 through the :ref:`Video Output <output>` interface.
162 * - ``V4L2_CAP_VIDEO_M2M`` 162 * - ``V4L2_CAP_VIDEO_M2M``
163 - 0x00008000 163 - 0x00008000
164 - The device supports the single-planar 164 - The device supports the single-planar API through the Video
165 Memory-To-Memory interface. 165 Memory-To-Memory interface.
166 * - ``V4L2_CAP_VIDEO_M2M_MPLANE`` 166 * - ``V4L2_CAP_VIDEO_M2M_MPLANE``
167 - 0x00004000 167 - 0x00004000
168 - The device supports the :ref:`multi-pl 168 - The device supports the :ref:`multi-planar API <planar-apis>`
169 through the Video Memory-To-Memory int 169 through the Video Memory-To-Memory interface.
170 * - ``V4L2_CAP_VIDEO_OVERLAY`` 170 * - ``V4L2_CAP_VIDEO_OVERLAY``
171 - 0x00000004 171 - 0x00000004
172 - The device supports the :ref:`Video Ov 172 - The device supports the :ref:`Video Overlay <overlay>`
173 interface. A video overlay device typi 173 interface. A video overlay device typically stores captured images
174 directly in the video memory of a grap 174 directly in the video memory of a graphics card, with hardware
175 clipping and scaling. 175 clipping and scaling.
176 * - ``V4L2_CAP_VBI_CAPTURE`` 176 * - ``V4L2_CAP_VBI_CAPTURE``
177 - 0x00000010 177 - 0x00000010
178 - The device supports the :ref:`Raw VBI 178 - The device supports the :ref:`Raw VBI Capture <raw-vbi>`
179 interface, providing Teletext and Clos 179 interface, providing Teletext and Closed Caption data.
180 * - ``V4L2_CAP_VBI_OUTPUT`` 180 * - ``V4L2_CAP_VBI_OUTPUT``
181 - 0x00000020 181 - 0x00000020
182 - The device supports the :ref:`Raw VBI 182 - The device supports the :ref:`Raw VBI Output <raw-vbi>`
183 interface. 183 interface.
184 * - ``V4L2_CAP_SLICED_VBI_CAPTURE`` 184 * - ``V4L2_CAP_SLICED_VBI_CAPTURE``
185 - 0x00000040 185 - 0x00000040
186 - The device supports the :ref:`Sliced V 186 - The device supports the :ref:`Sliced VBI Capture <sliced>`
187 interface. 187 interface.
188 * - ``V4L2_CAP_SLICED_VBI_OUTPUT`` 188 * - ``V4L2_CAP_SLICED_VBI_OUTPUT``
189 - 0x00000080 189 - 0x00000080
190 - The device supports the :ref:`Sliced V 190 - The device supports the :ref:`Sliced VBI Output <sliced>`
191 interface. 191 interface.
192 * - ``V4L2_CAP_RDS_CAPTURE`` 192 * - ``V4L2_CAP_RDS_CAPTURE``
193 - 0x00000100 193 - 0x00000100
194 - The device supports the :ref:`RDS <rds 194 - The device supports the :ref:`RDS <rds>` capture interface.
195 * - ``V4L2_CAP_VIDEO_OUTPUT_OVERLAY`` 195 * - ``V4L2_CAP_VIDEO_OUTPUT_OVERLAY``
196 - 0x00000200 196 - 0x00000200
197 - The device supports the :ref:`Video Ou 197 - The device supports the :ref:`Video Output Overlay <osd>` (OSD)
198 interface. Unlike the *Video Overlay* 198 interface. Unlike the *Video Overlay* interface, this is a
199 secondary function of video output dev 199 secondary function of video output devices and overlays an image
200 onto an outgoing video signal. When th 200 onto an outgoing video signal. When the driver sets this flag, it
201 must clear the ``V4L2_CAP_VIDEO_OVERLA 201 must clear the ``V4L2_CAP_VIDEO_OVERLAY`` flag and vice
202 versa. [#f1]_ 202 versa. [#f1]_
203 * - ``V4L2_CAP_HW_FREQ_SEEK`` 203 * - ``V4L2_CAP_HW_FREQ_SEEK``
204 - 0x00000400 204 - 0x00000400
205 - The device supports the 205 - The device supports the
206 :ref:`VIDIOC_S_HW_FREQ_SEEK` ioctl 206 :ref:`VIDIOC_S_HW_FREQ_SEEK` ioctl
207 for hardware frequency seeking. 207 for hardware frequency seeking.
208 * - ``V4L2_CAP_RDS_OUTPUT`` 208 * - ``V4L2_CAP_RDS_OUTPUT``
209 - 0x00000800 209 - 0x00000800
210 - The device supports the :ref:`RDS <rds 210 - The device supports the :ref:`RDS <rds>` output interface.
211 * - ``V4L2_CAP_TUNER`` 211 * - ``V4L2_CAP_TUNER``
212 - 0x00010000 212 - 0x00010000
213 - The device has some sort of tuner to r 213 - The device has some sort of tuner to receive RF-modulated video
214 signals. For more information about tu 214 signals. For more information about tuner programming see
215 :ref:`tuner`. 215 :ref:`tuner`.
216 * - ``V4L2_CAP_AUDIO`` 216 * - ``V4L2_CAP_AUDIO``
217 - 0x00020000 217 - 0x00020000
218 - The device has audio inputs or outputs 218 - The device has audio inputs or outputs. It may or may not support
219 audio recording or playback, in PCM or 219 audio recording or playback, in PCM or compressed formats. PCM
220 audio support must be implemented as A 220 audio support must be implemented as ALSA or OSS interface. For
221 more information on audio inputs and o 221 more information on audio inputs and outputs see :ref:`audio`.
222 * - ``V4L2_CAP_RADIO`` 222 * - ``V4L2_CAP_RADIO``
223 - 0x00040000 223 - 0x00040000
224 - This is a radio receiver. 224 - This is a radio receiver.
225 * - ``V4L2_CAP_MODULATOR`` 225 * - ``V4L2_CAP_MODULATOR``
226 - 0x00080000 226 - 0x00080000
227 - The device has some sort of modulator 227 - The device has some sort of modulator to emit RF-modulated
228 video/audio signals. For more informat 228 video/audio signals. For more information about modulator
229 programming see :ref:`tuner`. 229 programming see :ref:`tuner`.
230 * - ``V4L2_CAP_SDR_CAPTURE`` 230 * - ``V4L2_CAP_SDR_CAPTURE``
231 - 0x00100000 231 - 0x00100000
232 - The device supports the :ref:`SDR Capt 232 - The device supports the :ref:`SDR Capture <sdr>` interface.
233 * - ``V4L2_CAP_EXT_PIX_FORMAT`` 233 * - ``V4L2_CAP_EXT_PIX_FORMAT``
234 - 0x00200000 234 - 0x00200000
235 - The device supports the struct 235 - The device supports the struct
236 :c:type:`v4l2_pix_format` extended fie 236 :c:type:`v4l2_pix_format` extended fields.
237 * - ``V4L2_CAP_SDR_OUTPUT`` 237 * - ``V4L2_CAP_SDR_OUTPUT``
238 - 0x00400000 238 - 0x00400000
239 - The device supports the :ref:`SDR Outp 239 - The device supports the :ref:`SDR Output <sdr>` interface.
240 * - ``V4L2_CAP_META_CAPTURE`` 240 * - ``V4L2_CAP_META_CAPTURE``
241 - 0x00800000 241 - 0x00800000
242 - The device supports the :ref:`metadata 242 - The device supports the :ref:`metadata` capture interface.
243 * - ``V4L2_CAP_READWRITE`` 243 * - ``V4L2_CAP_READWRITE``
244 - 0x01000000 244 - 0x01000000
245 - The device supports the :c:func:`read( 245 - The device supports the :c:func:`read()` and/or
246 :c:func:`write()` I/O methods. 246 :c:func:`write()` I/O methods.
247 * - ``V4L2_CAP_EDID`` 247 * - ``V4L2_CAP_EDID``
248 - 0x02000000 248 - 0x02000000
249 - The device stores the EDID for a video 249 - The device stores the EDID for a video input, or retrieves the EDID for a video
250 output. It is a standalone EDID device 250 output. It is a standalone EDID device, so no video streaming etc. will take place.
251 251
252 For a video input this is typically an 252 For a video input this is typically an eeprom that supports the
253 :ref:`VESA Enhanced Display Data Chann 253 :ref:`VESA Enhanced Display Data Channel Standard <vesaeddc>`. It can be something
254 else as well, for example a micro cont 254 else as well, for example a micro controller.
255 255
256 For a video output this is typically r 256 For a video output this is typically read from an external device such as an
257 HDMI splitter accessed by a serial por 257 HDMI splitter accessed by a serial port.
258 * - ``V4L2_CAP_STREAMING`` 258 * - ``V4L2_CAP_STREAMING``
259 - 0x04000000 259 - 0x04000000
260 - The device supports the :ref:`streamin 260 - The device supports the :ref:`streaming <mmap>` I/O method.
261 * - ``V4L2_CAP_META_OUTPUT`` 261 * - ``V4L2_CAP_META_OUTPUT``
262 - 0x08000000 262 - 0x08000000
263 - The device supports the :ref:`metadata 263 - The device supports the :ref:`metadata` output interface.
264 * - ``V4L2_CAP_TOUCH`` 264 * - ``V4L2_CAP_TOUCH``
265 - 0x10000000 265 - 0x10000000
266 - This is a touch device. 266 - This is a touch device.
267 * - ``V4L2_CAP_IO_MC`` 267 * - ``V4L2_CAP_IO_MC``
268 - 0x20000000 268 - 0x20000000
269 - There is only one input and/or output 269 - There is only one input and/or output seen from userspace. The whole
270 video topology configuration, includin 270 video topology configuration, including which I/O entity is routed to
271 the input/output, is configured by use 271 the input/output, is configured by userspace via the Media Controller.
272 See :ref:`media_controller`. 272 See :ref:`media_controller`.
273 * - ``V4L2_CAP_DEVICE_CAPS`` 273 * - ``V4L2_CAP_DEVICE_CAPS``
274 - 0x80000000 274 - 0x80000000
275 - The driver fills the ``device_caps`` f 275 - The driver fills the ``device_caps`` field. This capability can
276 only appear in the ``capabilities`` fi 276 only appear in the ``capabilities`` field and never in the
277 ``device_caps`` field. 277 ``device_caps`` field.
278 278
279 Return Value 279 Return Value
280 ============ 280 ============
281 281
282 On success 0 is returned, on error -1 and the 282 On success 0 is returned, on error -1 and the ``errno`` variable is set
283 appropriately. The generic error codes are des 283 appropriately. The generic error codes are described at the
284 :ref:`Generic Error Codes <gen-errors>` chapte 284 :ref:`Generic Error Codes <gen-errors>` chapter.
285 285
286 .. [#f1] 286 .. [#f1]
287 The struct :c:type:`v4l2_framebuffer` lacks 287 The struct :c:type:`v4l2_framebuffer` lacks an
288 enum :c:type:`v4l2_buf_type` field, therefo 288 enum :c:type:`v4l2_buf_type` field, therefore the
289 type of overlay is implied by the driver ca 289 type of overlay is implied by the driver capabilities.
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