This might seem like a bit of a silly question, but I've been banging my head on the wall for a while on this. I need to add a single private control to the saa7115 driver. However, it's not clear to me exactly how this is supposed to work. The v4l2-ctl program will always use the extended controls interface for private controls, since the code only uses the g_ctrl ioctl if the class is V4L2_CTRL_CLASS_USER (and the control class for private controls is V4L2_CID_PRIVATE_BASE). However, if you look at the actual code in v4l2-ioctl.c, the call for g_ext_ctrls calls check_ext_ctrls(), which fails because "V4L2_CID_PRIVATE_BASE cannot be used as control class when using extended controls." The above two behaviors would seem to be conflicting. My original plan was to implement it as a non-extended control, but the v4l2-ctl application always sent the get call using the extended interface. So then I went to convert saa7115 to use the extended control interface, but then found out that the v4l2 core wouldn't allow an extended control to use a private control number. To make matters worse, the G_CTRL function that supposedly passes through calls to vidioc_g_ext_ctrl also calls check_ext_ctrl(), so if you want to have a private control then you would need to implement both the extended controls interface and the older g_ctrl in the driver (presumably the idea was that you would be able to only need to implement an extended controls interface, but that doesn't work given the above). I can change v4l2-ctl to use g_ctrl for private controls if we think that is the correct approach. But I didn't want to do that until I knew for sure that it is correct that you can never have a private extended control. Devin -- Devin J. Heitmueller - Kernel Labs http://www.kernellabs.com -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
