Hello, I've stumbled upon a problem when hacking the VLC v4l2 driver:
I want to enumerate all the private controls to make them available in the interface. The code used to enumerate the controls uses the same logic as Example 1-8 in the spec: http://v4l2spec.bytesex.org/spec-single/v4l2.html#AEN732 Unfortunately it doesn't work as expected. My webcam provides the following private controls: Backlight Compensation -> V4L2_CID_PRIVATE_BASE+0 Power Line Frequency -> V4L2_CID_PRIVATE_BASE+1 Sharpness -> V4L2_CID_PRIVATE_BASE+2 White Balance Temperature Auto -> V4L2_CID_PRIVATE_BASE+12 White Balance Temperature -> V4L2_CID_PRIVATE_BASE+13 Unfortunately, ioctl( fd, VIDIOC_QUERYCTRL, &queryctrl ) on V4L2_CID_PRIVATE_BASE+3 returns -1, which exits the private controls enumartion code. According to footnote [24] in the spec, "V4L2_CTRL_FLAG_DISABLED was intended for two purposes: Drivers can skip predefined controls not supported by the hardware (although returning EINVAL would do as well), or disable predefined and private controls after hardware detection without the trouble of reordering control arrays and indices (EINVAL cannot be used to skip private controls because it would prematurely end the enumeration)." If I understand that correctly, the ioctl (at least for private controls), should be succesfull for all the private controls supported by the uvcvideo drive and set the V4L2_CTRL_FLAG_DISABLED flag if that control isn't handled by the hardware. This would fix private control enumartion. Since I don't know the uvcvideo control code really well I haven't started patching it yet and would like a confirmation from the gurus that I'm reading the spec correctly. Thanks, -- Antoine Cellerier dionoea _______________________________________________ Linux-uvc-devel mailing list Linux-uvc-devel@lists.berlios.de https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
