From: Stefano Garzarella > Sent: 26 October 2020 09:39 > > On Mon, Oct 26, 2020 at 09:13:23AM +0000, David Laight wrote: > >From: Stefano Garzarella > >> Sent: 26 October 2020 08:43 > >... > >> >Isn't the canonical error for unknown ioctl codes -ENOTTY? > >> > > >> > >> Oh, thanks for pointing that out! > >> > >> I had not paid attention to the error returned, but looking at it I > >> noticed that perhaps the most appropriate would be -ENOIOCTLCMD. > >> In the ioctl syscall we return -ENOTTY, if the callback returns > >> -ENOIOCTLCMD. > >> > >> What do you think? > > > >It is 729 v 443 in favour of ENOTTY (based on grep). > > Under net/ it is 6 vs 83 in favour of ENOIOCTLCMD. > > > > >No idea where ENOIOCTLCMD comes from, but ENOTTY probably > >goes back to the early 1970s. > > Me too. > > > > >The fact that the ioctl wrapper converts the value is a good > >hint that userspace expects ENOTTY. > > Agree on that, but since we are not interfacing directly with userspace, > I think it is better to return the more specific error (ENOIOCTLCMD). I bet Linux thought it could use a different error code then found that 'unknown ioctl' was spelt ENOTTY. Back in the old days error values were probably almost unique. strerror(EAGIAN) was "No more processes" for a long time! David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
