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On a Webcam from Quanta, we see the following error. usb 3-5: New USB device found, idVendor=0408, idProduct=30d2, bcdDevice= 0.03 usb 3-5: New USB device strings: Mfr=3, Product=1, SerialNumber=2 usb 3-5: Product: USB2.0 HD UVC WebCam usb 3-5: Manufacturer: Quanta usb 3-5: SerialNumber: 0x0001 ... uvcvideo: Found UVC 1.10 device USB2.0 HD UVC WebCam (0408:30d2) uvcvideo: Failed to initialize entity for entity 5 uvcvideo: Failed to register entities (-22). The Webcam reports an entity of type UVC_VC_EXTENSION_UNIT. It reports a string index of '7' associated with that entity. The attempt to read that string from the camera fails with error -32 (-EPIPE). usb_string() returns that error, but it is ignored. As result, the entity name is empty. This later causes v4l2_device_register_subdev() to return -EINVAL, and no entities are registered as result. While this appears to be a firmware problem with the camera, the kernel should still handle the situation gracefully. To do that, check the return value from usb_string(). If it reports an error, assign the entity's default name. Signed-off-by: Guenter Roeck <linux@roeck-us.net> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.