UVC_SET_CUR Update the value of the control.Īpplications must set the ‘size’ field to the correct length for theĬontrol. UVC_GET_INFO Query the control information bitmap, which indicates whether UVC_GET_LEN Query the size of the control in bytes. the step size of theĪllowed control values. UVC_GET_RES Query the resolution of the control, i.e. UVC_GET_DEF Obtain the default value of the control. UVC_GET_MAX Obtain the maximum value of the control. UVC_GET_MIN Obtain the minimum value of the control. These requests are: UVC_GET_CUR Obtain the current value of the control. There are a number of different queries available that closelyĬorrespond to the low-level control requests described in the UVC This ioctl queries a UVC XU control identified by its extension unit ID For the time being they are still supported butĪpplication developers are encouraged to use UVCIOC_CTRL_QUERY instead.įor details on the UVCIOC_CTRL_QUERY ioctl please refer to the section titled UVCIOC_CTRL_SET ioctls have become obsolete since their functionality is a With the addition of the UVCIOC_CTRL_QUERY ioctl the UVCIOC_CTRL_GET and Supported) of the resulting byte indicate which requests are valid. UVC_GET_CUR or UVC_SET_CUR are valid requests for a given control, a UVC_GET_LEN requests in order to be able to allocate a sufficiently large bufferĪnd set the buffer size to the correct value. Unless the control size is already known it is necessary to first make a UVC descriptor or, if available, using the media controller API to enumerate a Hardcoded in the application or queried using other ways such as by parsing the In order to make such a request the UVC unit ID of the control’s extension unitĪnd the control selector need to be known. Purposes, firmware upload, or accessing binary controls, a second mechanism toĪccess XU controls is provided in the form of a driver-specific ioctl, namelyĪ call to this ioctl allows applications to send queries to the UVC driver thatĭirectly map to the low-level UVC control requests. This is no longer necessary as newer uvcvideo versions query the informationįor details on the UVCIOC_CTRL_MAP ioctl please refer to the section titledįor applications that need to access XU controls directly, e.g. Previous driver versions (before 0.2.0) required another ioctl to be usedīeforehand (UVCIOC_CTRL_ADD) to pass XU control information to the UVC driver. The ioctl used to create these control mappings is called UVCIOC_CTRL_MAP. Triggers a read or write of the associated XU control. However, reading or writing of such a V4L2 controls the stock controls, such asīrightness, contrast, etc.). Such controls appear andįunction exactly like normal V4L2 controls (i.e. Ranges thereof to be mapped to new V4L2 controls. These allow for individual XU controls or byte The UVC driver provides an API for user space applications to define so-calledĬontrol mappings at runtime.
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