diff options
Diffstat (limited to 'linux/Documentation/video4linux')
| -rw-r--r-- | linux/Documentation/video4linux/CARDLIST.bttv | 7 | ||||
| -rw-r--r-- | linux/Documentation/video4linux/CARDLIST.cx23885 | 1 | ||||
| -rw-r--r-- | linux/Documentation/video4linux/CARDLIST.cx88 | 3 | ||||
| -rw-r--r-- | linux/Documentation/video4linux/CARDLIST.em28xx | 8 | ||||
| -rw-r--r-- | linux/Documentation/video4linux/CARDLIST.saa7134 | 3 | ||||
| -rw-r--r-- | linux/Documentation/video4linux/bttv/CONTRIBUTORS | 2 | ||||
| -rw-r--r-- | linux/Documentation/video4linux/gspca.txt | 12 | ||||
| -rw-r--r-- | linux/Documentation/video4linux/v4l2-framework.txt | 520 |
8 files changed, 548 insertions, 8 deletions
diff --git a/linux/Documentation/video4linux/CARDLIST.bttv b/linux/Documentation/video4linux/CARDLIST.bttv index 60ba66836..0d93fa1ac 100644 --- a/linux/Documentation/video4linux/CARDLIST.bttv +++ b/linux/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/linux/Documentation/video4linux/CARDLIST.cx23885 b/linux/Documentation/video4linux/CARDLIST.cx23885 index 64823ccac..35ea130e9 100644 --- a/linux/Documentation/video4linux/CARDLIST.cx23885 +++ b/linux/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/linux/Documentation/video4linux/CARDLIST.cx88 b/linux/Documentation/video4linux/CARDLIST.cx88 index 12e600d74..0d08f1edc 100644 --- a/linux/Documentation/video4linux/CARDLIST.cx88 +++ b/linux/Documentation/video4linux/CARDLIST.cx88 @@ -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/linux/Documentation/video4linux/CARDLIST.em28xx b/linux/Documentation/video4linux/CARDLIST.em28xx index 187cc48d0..0c4c721da 100644 --- a/linux/Documentation/video4linux/CARDLIST.em28xx +++ b/linux/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) @@ -57,3 +57,5 @@ 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] + 59 -> Pinnacle PCTV HD Mini (em2874) [2304:023f] + 60 -> Hauppauge WinTV HVR 850 (em2883) [2040:651f] diff --git a/linux/Documentation/video4linux/CARDLIST.saa7134 b/linux/Documentation/video4linux/CARDLIST.saa7134 index dc67eef38..335aef4dc 100644 --- a/linux/Documentation/video4linux/CARDLIST.saa7134 +++ b/linux/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/linux/Documentation/video4linux/bttv/CONTRIBUTORS b/linux/Documentation/video4linux/bttv/CONTRIBUTORS index 8aad6dd93..eb41b2650 100644 --- a/linux/Documentation/video4linux/bttv/CONTRIBUTORS +++ b/linux/Documentation/video4linux/bttv/CONTRIBUTORS @@ -3,7 +3,7 @@ Contributors to bttv: Michael Chu <mmchu@pobox.com> AverMedia fix and more flexible card recognition -Alan Cox <alan@redhat.com> +Alan Cox <alan@lxorguk.ukuu.org.uk> Video4Linux interface and 2.1.x kernel adaptation Chris Kleitsch diff --git a/linux/Documentation/video4linux/gspca.txt b/linux/Documentation/video4linux/gspca.txt index 2a23fe31e..ec00740e6 100644 --- a/linux/Documentation/video4linux/gspca.txt +++ b/linux/Documentation/video4linux/gspca.txt @@ -169,6 +169,9 @@ 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 +202,8 @@ 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 @@ -214,9 +218,11 @@ 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: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 +255,13 @@ 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 @@ -263,7 +271,9 @@ 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/linux/Documentation/video4linux/v4l2-framework.txt b/linux/Documentation/video4linux/v4l2-framework.txt new file mode 100644 index 000000000..eeae76c22 --- /dev/null +++ b/linux/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); + |