diff options
Diffstat (limited to 'Documentation/video4linux')
| -rw-r--r-- | Documentation/video4linux/API.html | 43 | ||||
| -rw-r--r-- | Documentation/video4linux/CARDLIST.bttv | 7 | ||||
| -rw-r--r-- | Documentation/video4linux/CARDLIST.cx23885 | 1 | ||||
| -rw-r--r-- | Documentation/video4linux/CARDLIST.cx88 | 5 | ||||
| -rw-r--r-- | Documentation/video4linux/CARDLIST.em28xx | 9 | ||||
| -rw-r--r-- | Documentation/video4linux/CARDLIST.saa7134 | 3 | ||||
| -rw-r--r-- | Documentation/video4linux/README.cx88 | 8 | ||||
| -rw-r--r-- | Documentation/video4linux/gspca.txt | 19 | ||||
| -rw-r--r-- | Documentation/video4linux/v4l2-framework.txt | 520 |
9 files changed, 585 insertions, 30 deletions
diff --git a/Documentation/video4linux/API.html b/Documentation/video4linux/API.html index afbe9ae7ee96..d749d41f647b 100644 --- a/Documentation/video4linux/API.html +++ b/Documentation/video4linux/API.html @@ -1,16 +1,27 @@ -<TITLE>V4L API</TITLE> -<H1>Video For Linux APIs</H1> -<table border=0> -<tr> -<td> -<A HREF=http://www.linuxtv.org/downloads/video4linux/API/V4L1_API.html> -V4L original API</a> -</td><td> -Obsoleted by V4L2 API -</td></tr><tr><td> -<A HREF=http://www.linuxtv.org/downloads/video4linux/API/V4L2_API> -V4L2 API</a> -</td><td> -Should be used for new projects -</td></tr> -</table> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"> + <head> + <meta content="text/html;charset=ISO-8859-2" http-equiv="Content-Type" /> + <title>V4L API</title> + </head> + <body> + <h1>Video For Linux APIs</h1> + <table border="0"> + <tr> + <td> + <a href="http://www.linuxtv.org/downloads/video4linux/API/V4L1_API.html">V4L original API</a> + </td> + <td> + Obsoleted by V4L2 API + </td> + </tr> + <tr> + <td> + <a href="http://www.linuxtv.org/downloads/video4linux/API/V4L2_API">V4L2 API</a> + </td> + <td>Should be used for new projects + </td> + </tr> + </table> + </body> +</html> diff --git a/Documentation/video4linux/CARDLIST.bttv b/Documentation/video4linux/CARDLIST.bttv index 60ba66836038..0d93fa1ac25e 100644 --- a/Documentation/video4linux/CARDLIST.bttv +++ b/Documentation/video4linux/CARDLIST.bttv @@ -104,8 +104,8 @@ 103 -> Grand X-Guard / Trust 814PCI [0304:0102] 104 -> Nebula Electronics DigiTV [0071:0101] 105 -> ProVideo PV143 [aa00:1430,aa00:1431,aa00:1432,aa00:1433,aa03:1433] -106 -> PHYTEC VD-009-X1 MiniDIN (bt878) -107 -> PHYTEC VD-009-X1 Combi (bt878) +106 -> PHYTEC VD-009-X1 VD-011 MiniDIN (bt878) +107 -> PHYTEC VD-009-X1 VD-011 Combi (bt878) 108 -> PHYTEC VD-009 MiniDIN (bt878) 109 -> PHYTEC VD-009 Combi (bt878) 110 -> IVC-100 [ff00:a132] @@ -151,3 +151,6 @@ 150 -> Geovision GV-600 [008a:763c] 151 -> Kozumi KTV-01C 152 -> Encore ENL TV-FM-2 [1000:1801] +153 -> PHYTEC VD-012 (bt878) +154 -> PHYTEC VD-012-X1 (bt878) +155 -> PHYTEC VD-012-X2 (bt878) diff --git a/Documentation/video4linux/CARDLIST.cx23885 b/Documentation/video4linux/CARDLIST.cx23885 index 64823ccacd69..35ea130e9898 100644 --- a/Documentation/video4linux/CARDLIST.cx23885 +++ b/Documentation/video4linux/CARDLIST.cx23885 @@ -11,3 +11,4 @@ 10 -> DViCO FusionHDTV7 Dual Express [18ac:d618] 11 -> DViCO FusionHDTV DVB-T Dual Express [18ac:db78] 12 -> Leadtek Winfast PxDVR3200 H [107d:6681] + 13 -> Compro VideoMate E650F [185b:e800] diff --git a/Documentation/video4linux/CARDLIST.cx88 b/Documentation/video4linux/CARDLIST.cx88 index a5227e308f4a..0d08f1edcf6d 100644 --- a/Documentation/video4linux/CARDLIST.cx88 +++ b/Documentation/video4linux/CARDLIST.cx88 @@ -2,7 +2,7 @@ 1 -> Hauppauge WinTV 34xxx models [0070:3400,0070:3401] 2 -> GDI Black Gold [14c7:0106,14c7:0107] 3 -> PixelView [1554:4811] - 4 -> ATI TV Wonder Pro [1002:00f8] + 4 -> ATI TV Wonder Pro [1002:00f8,1002:00f9] 5 -> Leadtek Winfast 2000XP Expert [107d:6611,107d:6613] 6 -> AverTV Studio 303 (M126) [1461:000b] 7 -> MSI TV-@nywhere Master [1462:8606] @@ -74,3 +74,6 @@ 73 -> TeVii S420 DVB-S [d420:9022] 74 -> Prolink Pixelview Global Extreme [1554:4976] 75 -> PROF 7300 DVB-S/S2 [B033:3033] + 76 -> SATTRADE ST4200 DVB-S/S2 [b200:4200] + 77 -> TBS 8910 DVB-S [8910:8888] + 78 -> Prof 6200 DVB-S [b022:3022] diff --git a/Documentation/video4linux/CARDLIST.em28xx b/Documentation/video4linux/CARDLIST.em28xx index 187cc48d0924..75bded8a4aa2 100644 --- a/Documentation/video4linux/CARDLIST.em28xx +++ b/Documentation/video4linux/CARDLIST.em28xx @@ -1,5 +1,5 @@ 0 -> Unknown EM2800 video grabber (em2800) [eb1a:2800] - 1 -> Unknown EM2750/28xx video grabber (em2820/em2840) [eb1a:2820,eb1a:2860,eb1a:2861,eb1a:2870,eb1a:2881,eb1a:2883] + 1 -> Unknown EM2750/28xx video grabber (em2820/em2840) [eb1a:2820,eb1a:2821,eb1a:2860,eb1a:2861,eb1a:2870,eb1a:2881,eb1a:2883] 2 -> Terratec Cinergy 250 USB (em2820/em2840) [0ccd:0036] 3 -> Pinnacle PCTV USB 2 (em2820/em2840) [2304:0208] 4 -> Hauppauge WinTV USB 2 (em2820/em2840) [2040:4200,2040:4201] @@ -12,9 +12,9 @@ 11 -> Terratec Hybrid XS (em2880) [0ccd:0042] 12 -> Kworld PVR TV 2800 RF (em2820/em2840) 13 -> Terratec Prodigy XS (em2880) [0ccd:0047] - 14 -> Pixelview Prolink PlayTV USB 2.0 (em2820/em2840) [eb1a:2821] + 14 -> Pixelview Prolink PlayTV USB 2.0 (em2820/em2840) 15 -> V-Gear PocketTV (em2800) - 16 -> Hauppauge WinTV HVR 950 (em2883) [2040:6513,2040:6517,2040:651b,2040:651f] + 16 -> Hauppauge WinTV HVR 950 (em2883) [2040:6513,2040:6517,2040:651b] 17 -> Pinnacle PCTV HD Pro Stick (em2880) [2304:0227] 18 -> Hauppauge WinTV HVR 900 (R2) (em2880) [2040:6502] 19 -> PointNix Intra-Oral Camera (em2860) @@ -27,7 +27,6 @@ 26 -> Hercules Smart TV USB 2.0 (em2820/em2840) 27 -> Pinnacle PCTV USB 2 (Philips FM1216ME) (em2820/em2840) 28 -> Leadtek Winfast USB II Deluxe (em2820/em2840) - 29 -> Pinnacle Dazzle DVC 100 (em2820/em2840) 30 -> Videology 20K14XUSB USB2.0 (em2820/em2840) 31 -> Usbgear VD204v9 (em2821) 32 -> Supercomp USB 2.0 TV (em2821) @@ -57,3 +56,5 @@ 56 -> Pinnacle Hybrid Pro (2) (em2882) [2304:0226] 57 -> Kworld PlusTV HD Hybrid 330 (em2883) [eb1a:a316] 58 -> Compro VideoMate ForYou/Stereo (em2820/em2840) [185b:2041] + 60 -> Hauppauge WinTV HVR 850 (em2883) [2040:651f] + 61 -> Pixelview PlayTV Box 4 USB 2.0 (em2820/em2840) diff --git a/Documentation/video4linux/CARDLIST.saa7134 b/Documentation/video4linux/CARDLIST.saa7134 index dc67eef38ff9..335aef4dcaeb 100644 --- a/Documentation/video4linux/CARDLIST.saa7134 +++ b/Documentation/video4linux/CARDLIST.saa7134 @@ -10,7 +10,7 @@ 9 -> Medion 5044 10 -> Kworld/KuroutoShikou SAA7130-TVPCI 11 -> Terratec Cinergy 600 TV [153b:1143] - 12 -> Medion 7134 [16be:0003] + 12 -> Medion 7134 [16be:0003,16be:5000] 13 -> Typhoon TV+Radio 90031 14 -> ELSA EX-VISION 300TV [1048:226b] 15 -> ELSA EX-VISION 500TV [1048:226a] @@ -151,3 +151,4 @@ 150 -> Zogis Real Angel 220 151 -> ADS Tech Instant HDTV [1421:0380] 152 -> Asus Tiger Rev:1.00 [1043:4857] +153 -> Kworld Plus TV Analog Lite PCI [17de:7128] diff --git a/Documentation/video4linux/README.cx88 b/Documentation/video4linux/README.cx88 index 166d5960b1a9..35fae23f883b 100644 --- a/Documentation/video4linux/README.cx88 +++ b/Documentation/video4linux/README.cx88 @@ -1,4 +1,3 @@ - cx8800 release notes ==================== @@ -10,21 +9,20 @@ current status video - Basically works. - - Some minor image quality glitches. - - For now only capture, overlay support isn't completed yet. + - For now, only capture and read(). Overlay isn't supported. audio - The chip specs for the on-chip TV sound decoder are next to useless :-/ - Neverless the builtin TV sound decoder starts working now, - at least for PAL-BG. Other TV norms need other code ... + at least for some standards. FOR ANY REPORTS ON THIS PLEASE MENTION THE TV NORM YOU ARE USING. - Most tuner chips do provide mono sound, which may or may not be useable depending on the board design. With the Hauppauge cards it works, so there is mono sound available as fallback. - audio data dma (i.e. recording without loopback cable to the - sound card) should be possible, but there is no code yet ... + sound card) is supported via cx88-alsa. vbi - Code present. Works for NTSC closed caption. PAL and other diff --git a/Documentation/video4linux/gspca.txt b/Documentation/video4linux/gspca.txt index 004818fab040..1c58a7630146 100644 --- a/Documentation/video4linux/gspca.txt +++ b/Documentation/video4linux/gspca.txt @@ -50,9 +50,14 @@ ov519 045e:028c Micro$oft xbox cam spca508 0461:0815 Micro Innovation IC200 sunplus 0461:0821 Fujifilm MV-1 zc3xx 0461:0a00 MicroInnovation WebCam320 +stv06xx 046d:0840 QuickCam Express +stv06xx 046d:0850 LEGO cam / QuickCam Web +stv06xx 046d:0870 Dexxa WebCam USB spca500 046d:0890 Logitech QuickCam traveler vc032x 046d:0892 Logitech Orbicam vc032x 046d:0896 Logitech Orbicam +vc032x 046d:0897 Logitech QuickCam for Dell notebooks +zc3xx 046d:089d Logitech QuickCam E2500 zc3xx 046d:08a0 Logitech QC IM zc3xx 046d:08a1 Logitech QC IM 0x08A1 +sound zc3xx 046d:08a2 Labtec Webcam Pro @@ -169,6 +174,9 @@ spca500 06bd:0404 Agfa CL20 spca500 06be:0800 Optimedia sunplus 06d6:0031 Trust 610 LCD PowerC@m Zoom spca506 06e1:a190 ADS Instant VCD +ov534 06f8:3002 Hercules Blog Webcam +ov534 06f8:3003 Hercules Dualpix HD Weblog +sonixj 06f8:3004 Hercules Classic Silver spca508 0733:0110 ViewQuest VQ110 spca508 0130:0130 Clone Digital Webcam 11043 spca501 0733:0401 Intel Create and Share @@ -199,7 +207,8 @@ sunplus 08ca:2050 Medion MD 41437 sunplus 08ca:2060 Aiptek PocketDV5300 tv8532 0923:010f ICM532 cams mars 093a:050f Mars-Semi Pc-Camera -pac207 093a:2460 PAC207 Qtec Webcam 100 +pac207 093a:2460 Qtec Webcam 100 +pac207 093a:2461 HP Webcam pac207 093a:2463 Philips SPC 220 NC pac207 093a:2464 Labtec Webcam 1200 pac207 093a:2468 PAC207 @@ -213,10 +222,13 @@ pac7311 093a:2603 PAC7312 pac7311 093a:2608 Trust WB-3300p pac7311 093a:260e Gigaware VGA PC Camera, Trust WB-3350p, SIGMA cam 2350 pac7311 093a:260f SnakeCam +pac7311 093a:2620 Apollo AC-905 pac7311 093a:2621 PAC731x +pac7311 093a:2622 Genius Eye 312 pac7311 093a:2624 PAC7302 pac7311 093a:2626 Labtec 2200 pac7311 093a:262a Webcam 300k +pac7311 093a:262c Philips SPC 230 NC zc3xx 0ac8:0302 Z-star Vimicro zc0302 vc032x 0ac8:0321 Vimicro generic vc0321 vc032x 0ac8:0323 Vimicro Vc0323 @@ -249,11 +261,13 @@ sonixj 0c45:60c0 Sangha Sn535 sonixj 0c45:60ec SN9C105+MO4000 sonixj 0c45:60fb Surfer NoName sonixj 0c45:60fc LG-LIC300 +sonixj 0c45:60fe Microdia Audio sonixj 0c45:6128 Microdia/Sonix SNP325 sonixj 0c45:612a Avant Camera sonixj 0c45:612c Typhoon Rasy Cam 1.3MPix sonixj 0c45:6130 Sonix Pccam sonixj 0c45:6138 Sn9c120 Mo4000 +sonixj 0c45:613a Microdia Sonix PC Camera sonixj 0c45:613b Surfer SN-206 sonixj 0c45:613c Sonix Pccam168 sonixj 0c45:6143 Sonix Pccam168 @@ -263,6 +277,9 @@ etoms 102c:6251 Qcam xxxxxx VGA zc3xx 10fd:0128 Typhoon Webshot II USB 300k 0x0128 spca561 10fd:7e50 FlyCam Usb 100 zc3xx 10fd:8050 Typhoon Webshot II USB 300k +ov534 1415:2000 Sony HD Eye for PS3 (SLEH 00201) +pac207 145f:013a Trust WB-1300N +vc032x 15b8:6002 HP 2.0 Megapixel rz406aa spca501 1776:501c Arowana 300K CMOS Camera t613 17a1:0128 TASCORP JPEG Webcam, NGS Cyclops vc032x 17ef:4802 Lenovo Vc0323+MI1310_SOC diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt new file mode 100644 index 000000000000..eeae76c22a93 --- /dev/null +++ b/Documentation/video4linux/v4l2-framework.txt @@ -0,0 +1,520 @@ +Overview of the V4L2 driver framework +===================================== + +This text documents the various structures provided by the V4L2 framework and +their relationships. + + +Introduction +------------ + +The V4L2 drivers tend to be very complex due to the complexity of the +hardware: most devices have multiple ICs, export multiple device nodes in +/dev, and create also non-V4L2 devices such as DVB, ALSA, FB, I2C and input +(IR) devices. + +Especially the fact that V4L2 drivers have to setup supporting ICs to +do audio/video muxing/encoding/decoding makes it more complex than most. +Usually these ICs are connected to the main bridge driver through one or +more I2C busses, but other busses can also be used. Such devices are +called 'sub-devices'. + +For a long time the framework was limited to the video_device struct for +creating V4L device nodes and video_buf for handling the video buffers +(note that this document does not discuss the video_buf framework). + +This meant that all drivers had to do the setup of device instances and +connecting to sub-devices themselves. Some of this is quite complicated +to do right and many drivers never did do it correctly. + +There is also a lot of common code that could never be refactored due to +the lack of a framework. + +So this framework sets up the basic building blocks that all drivers +need and this same framework should make it much easier to refactor +common code into utility functions shared by all drivers. + + +Structure of a driver +--------------------- + +All drivers have the following structure: + +1) A struct for each device instance containing the device state. + +2) A way of initializing and commanding sub-devices (if any). + +3) Creating V4L2 device nodes (/dev/videoX, /dev/vbiX, /dev/radioX and + /dev/vtxX) and keeping track of device-node specific data. + +4) Filehandle-specific structs containing per-filehandle data. + +This is a rough schematic of how it all relates: + + device instances + | + +-sub-device instances + | + \-V4L2 device nodes + | + \-filehandle instances + + +Structure of the framework +-------------------------- + +The framework closely resembles the driver structure: it has a v4l2_device +struct for the device instance data, a v4l2_subdev struct to refer to +sub-device instances, the video_device struct stores V4L2 device node data +and in the future a v4l2_fh struct will keep track of filehandle instances +(this is not yet implemented). + + +struct v4l2_device +------------------ + +Each device instance is represented by a struct v4l2_device (v4l2-device.h). +Very simple devices can just allocate this struct, but most of the time you +would embed this struct inside a larger struct. + +You must register the device instance: + + v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev); + +Registration will initialize the v4l2_device struct and link dev->driver_data +to v4l2_dev. Registration will also set v4l2_dev->name to a value derived from +dev (driver name followed by the bus_id, to be precise). You may change the +name after registration if you want. + +The first 'dev' argument is normally the struct device pointer of a pci_dev, +usb_device or platform_device. + +You unregister with: + + v4l2_device_unregister(struct v4l2_device *v4l2_dev); + +Unregistering will also automatically unregister all subdevs from the device. + +Sometimes you need to iterate over all devices registered by a specific +driver. This is usually the case if multiple device drivers use the same +hardware. E.g. the ivtvfb driver is a framebuffer driver that uses the ivtv +hardware. The same is true for alsa drivers for example. + +You can iterate over all registered devices as follows: + +static int callback(struct device *dev, void *p) +{ + struct v4l2_device *v4l2_dev = dev_get_drvdata(dev); + + /* test if this device was inited */ + if (v4l2_dev == NULL) + return 0; + ... + return 0; +} + +int iterate(void *p) +{ + struct device_driver *drv; + int err; + + /* Find driver 'ivtv' on the PCI bus. + pci_bus_type is a global. For USB busses use usb_bus_type. */ + drv = driver_find("ivtv", &pci_bus_type); + /* iterate over all ivtv device instances */ + err = driver_for_each_device(drv, NULL, p, callback); + put_driver(drv); + return err; +} + +Sometimes you need to keep a running counter of the device instance. This is +commonly used to map a device instance to an index of a module option array. + +The recommended approach is as follows: + +static atomic_t drv_instance = ATOMIC_INIT(0); + +static int __devinit drv_probe(struct pci_dev *dev, + const struct pci_device_id *pci_id) +{ + ... + state->instance = atomic_inc_return(&drv_instance) - 1; +} + + +struct v4l2_subdev +------------------ + +Many drivers need to communicate with sub-devices. These devices can do all +sort of tasks, but most commonly they handle audio and/or video muxing, +encoding or decoding. For webcams common sub-devices are sensors and camera +controllers. + +Usually these are I2C devices, but not necessarily. In order to provide the +driver with a consistent interface to these sub-devices the v4l2_subdev struct +(v4l2-subdev.h) was created. + +Each sub-device driver must have a v4l2_subdev struct. This struct can be +stand-alone for simple sub-devices or it might be embedded in a larger struct +if more state information needs to be stored. Usually there is a low-level +device struct (e.g. i2c_client) that contains the device data as setup +by the kernel. It is recommended to store that pointer in the private +data of v4l2_subdev using v4l2_set_subdevdata(). That makes it easy to go +from a v4l2_subdev to the actual low-level bus-specific device data. + +You also need a way to go from the low-level struct to v4l2_subdev. For the +common i2c_client struct the i2c_set_clientdata() call is used to store a +v4l2_subdev pointer, for other busses you may have to use other methods. + +From the bridge driver perspective you load the sub-device module and somehow +obtain the v4l2_subdev pointer. For i2c devices this is easy: you call +i2c_get_clientdata(). For other busses something similar needs to be done. +Helper functions exists for sub-devices on an I2C bus that do most of this +tricky work for you. + +Each v4l2_subdev contains function pointers that sub-device drivers can +implement (or leave NULL if it is not applicable). Since sub-devices can do +so many different things and you do not want to end up with a huge ops struct +of which only a handful of ops are commonly implemented, the function pointers +are sorted according to category and each category has its own ops struct. + +The top-level ops struct contains pointers to the category ops structs, which +may be NULL if the subdev driver does not support anything from that category. + +It looks like this: + +struct v4l2_subdev_core_ops { + int (*g_chip_ident)(struct v4l2_subdev *sd, struct v4l2_chip_ident *chip); + int (*log_status)(struct v4l2_subdev *sd); + int (*init)(struct v4l2_subdev *sd, u32 val); + ... +}; + +struct v4l2_subdev_tuner_ops { + ... +}; + +struct v4l2_subdev_audio_ops { + ... +}; + +struct v4l2_subdev_video_ops { + ... +}; + +struct v4l2_subdev_ops { + const struct v4l2_subdev_core_ops *core; + const struct v4l2_subdev_tuner_ops *tuner; + const struct v4l2_subdev_audio_ops *audio; + const struct v4l2_subdev_video_ops *video; +}; + +The core ops are common to all subdevs, the other categories are implemented +depending on the sub-device. E.g. a video device is unlikely to support the +audio ops and vice versa. + +This setup limits the number of function pointers while still making it easy +to add new ops and categories. + +A sub-device driver initializes the v4l2_subdev struct using: + + v4l2_subdev_init(subdev, &ops); + +Afterwards you need to initialize subdev->name with a unique name and set the +module owner. This is done for you if you use the i2c helper functions. + +A device (bridge) driver needs to register the v4l2_subdev with the +v4l2_device: + + int err = v4l2_device_register_subdev(device, subdev); + +This can fail if the subdev module disappeared before it could be registered. +After this function was called successfully the subdev->dev field points to +the v4l2_device. + +You can unregister a sub-device using: + + v4l2_device_unregister_subdev(subdev); + +Afterwards the subdev module can be unloaded and subdev->dev == NULL. + +You can call an ops function either directly: + + err = subdev->ops->core->g_chip_ident(subdev, &chip); + +but it is better and easier to use this macro: + + err = v4l2_subdev_call(subdev, core, g_chip_ident, &chip); + +The macro will to the right NULL pointer checks and returns -ENODEV if subdev +is NULL, -ENOIOCTLCMD if either subdev->core or subdev->core->g_chip_ident is +NULL, or the actual result of the subdev->ops->core->g_chip_ident ops. + +It is also possible to call all or a subset of the sub-devices: + + v4l2_device_call_all(dev, 0, core, g_chip_ident, &chip); + +Any subdev that does not support this ops is skipped and error results are +ignored. If you want to check for errors use this: + + err = v4l2_device_call_until_err(dev, 0, core, g_chip_ident, &chip); + +Any error except -ENOIOCTLCMD will exit the loop with that error. If no +errors (except -ENOIOCTLCMD) occured, then 0 is returned. + +The second argument to both calls is a group ID. If 0, then all subdevs are +called. If non-zero, then only those whose group ID match that value will +be called. Before a bridge driver registers a subdev it can set subdev->grp_id +to whatever value it wants (it's 0 by default). This value is owned by the +bridge driver and the sub-device driver will never modify or use it. + +The group ID gives the bridge driver more control how callbacks are called. +For example, there may be multiple audio chips on a board, each capable of +changing the volume. But usually only one will actually be used when the +user want to change the volume. You can set the group ID for that subdev to +e.g. AUDIO_CONTROLLER and specify that as the group ID value when calling +v4l2_device_call_all(). That ensures that it will only go to the subdev +that needs it. + +The advantage of using v4l2_subdev is that it is a generic struct and does +not contain any knowledge about the underlying hardware. So a driver might +contain several subdevs that use an I2C bus, but also a subdev that is +controlled through GPIO pins. This distinction is only relevant when setting +up the device, but once the subdev is registered it is completely transparent. + + +I2C sub-device drivers +---------------------- + +Since these drivers are so common, special helper functions are available to +ease the use of these drivers (v4l2-common.h). + +The recommended method of adding v4l2_subdev support to an I2C driver is to +embed the v4l2_subdev struct into the state struct that is created for each +I2C device instance. Very simple devices have no state struct and in that case +you can just create a v4l2_subdev directly. + +A typical state struct would look like this (where 'chipname' is replaced by +the name of the chip): + +struct chipname_state { + struct v4l2_subdev sd; + ... /* additional state fields */ +}; + +Initialize the v4l2_subdev struct as follows: + + v4l2_i2c_subdev_init(&state->sd, client, subdev_ops); + +This function will fill in all the fields of v4l2_subdev and ensure that the +v4l2_subdev and i2c_client both point to one another. + +You should also add a helper inline function to go from a v4l2_subdev pointer +to a chipname_state struct: + +static inline struct chipname_state *to_state(struct v4l2_subdev *sd) +{ + return container_of(sd, struct chipname_state, sd); +} + +Use this to go from the v4l2_subdev struct to the i2c_client struct: + + struct i2c_client *client = v4l2_get_subdevdata(sd); + +And this to go from an i2c_client to a v4l2_subdev struct: + + struct v4l2_subdev *sd = i2c_get_clientdata(client); + +Finally you need to make a command function to make driver->command() +call the right subdev_ops functions: + +static int subdev_command(struct i2c_client *client, unsigned cmd, void *arg) +{ + return v4l2_subdev_command(i2c_get_clientdata(client), cmd, arg); +} + +If driver->command is never used then you can leave this out. Eventually the +driver->command usage should be removed from v4l. + +Make sure to call v4l2_device_unregister_subdev(sd) when the remove() callback +is called. This will unregister the sub-device from the bridge driver. It is +safe to call this even if the sub-device was never registered. + + +The bridge driver also has some helper functions it can use: + +struct v4l2_subdev *sd = v4l2_i2c_new_subdev(adapter, "module_foo", "chipid", 0x36); + +This loads the given module (can be NULL if no module needs to be loaded) and +calls i2c_new_device() with the given i2c_adapter and chip/address arguments. +If all goes well, then it registers the subdev with the v4l2_device. It gets +the v4l2_device by calling i2c_get_adapdata(adapter), so you should make sure +that adapdata is set to v4l2_device when you setup the i2c_adapter in your +driver. + +You can also use v4l2_i2c_new_probed_subdev() which is very similar to +v4l2_i2c_new_subdev(), except that it has an array of possible I2C addresses +that it should probe. Internally it calls i2c_new_probed_device(). + +Both functions return NULL if something went wrong. + + +struct video_device +------------------- + +The actual device nodes in the /dev directory are created using the +video_device struct (v4l2-dev.h). This struct can either be allocated +dynamically or embedded in a larger struct. + +To allocate it dynamically use: + + struct video_device *vdev = video_device_alloc(); + + if (vdev == NULL) + return -ENOMEM; + + vdev->release = video_device_release; + +If you embed it in a larger struct, then you must set the release() +callback to your own function: + + struct video_device *vdev = &my_vdev->vdev; + + vdev->release = my_vdev_release; + +The release callback must be set and it is called when the last user +of the video device exits. + +The default video_device_release() callback just calls kfree to free the +allocated memory. + +You should also set these fields: + +- parent: set to the parent device (same device as was used to register + v4l2_device). +- name: set to something descriptive and unique. +- fops: set to the file_operations struct. +- ioctl_ops: if you use the v4l2_ioctl_ops to simplify ioctl maintenance + (highly recommended to use this and it might become compulsory in the + future!), then set this to your v4l2_ioctl_ops struct. + +If you use v4l2_ioctl_ops, then you should set .unlocked_ioctl to +__video_ioctl2 or .ioctl to video_ioctl2 in your file_operations struct. + + +video_device registration +------------------------- + +Next you register the video device: this will create the character device +for you. + + err = video_register_device(vdev, VFL_TYPE_GRABBER, -1); + if (err) { + video_device_release(vdev); // or kfree(my_vdev); + return err; + } + +Which device is registered depends on the type argument. The following +types exist: + +VFL_TYPE_GRABBER: videoX for video input/output devices +VFL_TYPE_VBI: vbiX for vertical blank data (i.e. closed captions, teletext) +VFL_TYPE_RADIO: radioX for radio tuners +VFL_TYPE_VTX: vtxX for teletext devices (deprecated, don't use) + +The last argument gives you a certain amount of control over the device +kernel number used (i.e. the X in videoX). Normally you will pass -1 to +let the v4l2 framework pick the first free number. But if a driver creates +many devices, then it can be useful to have different video devices in +separate ranges. For example, video capture devices start at 0, video +output devices start at 16. + +So you can use the last argument to specify a minimum kernel number and +the v4l2 framework will try to pick the first free number that is equal +or higher to what you passed. If that fails, then it will just pick the +first free number. + +Whenever a device node is created some attributes are also created for you. +If you look in /sys/class/video4linux you see the devices. Go into e.g. +video0 and you will see 'name' and 'index' attributes. The 'name' attribute +is the 'name' field of the video_device struct. The 'index' attribute is +a device node index that can be assigned by the driver, or that is calculated +for you. + +If you call video_register_device(), then the index is just increased by +1 for each device node you register. The first video device node you register +always starts off with 0. + +Alternatively you can call video_register_device_index() which is identical +to video_register_device(), but with an extra index argument. Here you can +pass a specific index value (between 0 and 31) that should be used. + +Users can setup udev rules that utilize the index attribute to make fancy +device names (e.g. 'mpegX' for MPEG video capture device nodes). + +After the device was successfully registered, then you can use these fields: + +- vfl_type: the device type passed to video_register_device. +- minor: the assigned device minor number. +- num: the device kernel number (i.e. the X in videoX). +- index: the device index number (calculated or set explicitly using + video_register_device_index). + +If the registration failed, then you need to call video_device_release() +to free the allocated video_device struct, or free your own struct if the +video_device was embedded in it. The vdev->release() callback will never +be called if the registration failed, nor should you ever attempt to +unregister the device if the registration failed. + + +video_device cleanup +-------------------- + +When the video device nodes have to be removed, either during the unload +of the driver or because the USB device was disconnected, then you should +unregister them: + + video_unregister_device(vdev); + +This will remove the device nodes from sysfs (causing udev to remove them +from /dev). + +After video_unregister_device() returns no new opens can be done. + +However, in the case of USB devices some application might still have one +of these device nodes open. You should block all new accesses to read, +write, poll, etc. except possibly for certain ioctl operations like +queueing buffers. + +When the last user of the video device node exits, then the vdev->release() +callback is called and you can do the final cleanup there. + + +video_device helper functions +----------------------------- + +There are a few useful helper functions: + +You can set/get driver private data in the video_device struct using: + +void *video_get_drvdata(struct video_device *dev); +void video_set_drvdata(struct video_device *dev, void *data); + +Note that you can safely call video_set_drvdata() before calling +video_register_device(). + +And this function: + +struct video_device *video_devdata(struct file *file); + +returns the video_device belonging to the file struct. + +The final helper function combines video_get_drvdata with +video_devdata: + +void *video_drvdata(struct file *file); + +You can go from a video_device struct to the v4l2_device struct using: + +struct v4l2_device *v4l2_dev = dev_get_drvdata(vdev->parent); + |
