Hey all, Disclaimer: I am very new to the kernel space so apologies for any newb mistakes. I am working on trying to enable the UVC gadget driver on an Android Device. The device already supports configfs and has a few gadget functions already working. ADB (f_fs) and USB Tethering (f_ncm) are the ones I tested with. I added CONFIG_USB_CONFIGFS_F_UVC=y to the kernel's config, was able to create a uvc function following the example in https://docs.kernel.org/usb/gadget-testing.html#uvc-function. After symlinking the uvc function to configfs, when the gadget is pulled up I see that all functions including UVC are bound to the composite gadget without any errors. However, while the UVC function is linked, no other function can communicate over their endpoints. The host is able to enumerate all the functions, but is unable to read from or write to non-uvc endpoints. Removing the UVC function from configfs and pulling up the gadget again restores all other functions. Testing the UVC gadget shows that the UVC driver is functioning properly and a linux host is able to communicate with the UVC gadget over V4L2 as expected. AFAICT, there are no kernel logs showing errors in reading/writing to endpoints even after enabling debug logs. Some rudimentary debugging shows that the endpoints of other functions stop responding if the UVC gadget writes its usb descriptors to its usb_function in uvc_function_bind. I stub out all functionality from the uvc gadget (except alloc and free), the other functions work properly. But if I unstub uvc_function_bind to go as far as writing the descriptor in fs_descriptors (f_uvc.c, uvc_function_bind line#713), the other functions stop working. Is this a known issue, or am I missing something obvious? Any help would be appreciated! Misc info: - Kernel Version: 5.10.107 - USB controller: DWC3 (unfortunately, I don't have devices with any other controllers available) - Changes made: None. The gadget drivers show this behavior without any changes. I tried to copy over changes from ToT https://github.com/torvalds/linux/blob/master/drivers/usb/gadget/function/f_uvc.c which fixed some crashes, but this behavior sticks. Thank you! - Avi
