On Tuesday 06 December 2011, Ming Lei wrote: > > Using an array added to the end of the v4l2_fd_result structure > > rather than a pointer would really make this easier IMHO. > > I have tried to do this, but video_usercopy needs a few changes > to handle array args if no indirect pointer is passed to kernel. Ah, I see. Or you would have to encode the array size into the ioctl command, which is also ugly in a different way. > I am not sure if media guys are happy to accept the changes, :-) Maybe Mauro can comment on which solution he prefers then, given the choice between: 1. adding another handler in drivers/media/video/v4l2-compat-ioctl32.c 2. passing a pointer that is casted to __u64 in user space an back in the kernel 3. extending video_usercopy in some way to make this work, preferably in a generic way. 4. using a variable command number like #define VIDIOC_G_FD_RESULT(num) _IOC(_IOC_READ|_IOC_WRITE,'V', 95, \ sizeof(struct v4l2_fd_result) + (num) * sizeof(struct v4l2_fd_detection) 5. requiring the interface to be simplified to return only a single struct v4l2_fd_detection at a time I agree that none of these are nice. My preferred option would be last one, but I don't know how performance critical the interface is or if it would cause any races that you want to avoid. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
