On Tue, 21 Apr 2015, Dave Mielke wrote: > [quoted lines by Alan Stern on 2015/04/21 at 10:50 -0400] > > >Yes, it's okay. A userspace ABI like that isn't going to go away. > >It's also true that you can poll for POLLERR or POLLHUP to see when a > >device has been disconnected, although libusb probably isn't interested > >in doing that. > > Out of curiosity, do you know why one must poll for output (rather than for > input)? I have no idea. Perhaps someone decided to do it that way because you need to have the file open for writing before you can submit or reap URBs. > JDoes "writability" precisely mean that there's at least one > user-submitted URB that can now be reaped? Yes. The exact test is: if (file->f_mode & FMODE_WRITE && !list_empty(&ps->async_completed)) mask |= POLLOUT | POLLWRNORM; where ps->async_completed is the list of completed but not-yet-reaped URBs. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
