Hello. My name is Brent Weatherall. I am new to developing with the UVC. I am developing in Linux. I have a device that uses an extension unit. Looking at the device's last generation of software for the extension unit portion of the device I do not see 100% of the correlation with the UVC XU documentation. The old device code (which functions properly) does not actually use the extension descriptor in the software at all, yet it works anyway. The extension descriptor does not show up in the uvcvideo.h file either. My questions are as follows:
1. Is this XU descriptor something agreed upon on paper and then implemented solely inside the device? 2. When sending the first xu control via ioctl to activate the specified xu control, is the bUnitID from the descriptor specification the same thing as the "__u8 unit" field in the data structure "struct uvc_xu_control"? 3. Is it correct that when using an XU control, it takes two ioctl commands? One to specify the control to use, and then one to actually get/send the control data? 4. If 3 is correct, when sending the first xu control via ioctl, what should be put in the '__u8 selector', '__u16 size' and '__u8 *data' fields? 5. How does one determine the size of an XU control? Sorry if these questions are basic or should be obvious; however, they are not clear to me at this time from reading the UVC documentation. Thanks. Brent
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