Subject: [PATCH 1/3] tty/serial_core: add ISO7816 infrastructure

From: [email-masked] (Alan Cox)
Date: Thu, 19 Jul 2018 12:07:05 +0100

> >   
> > > +	if (!port->iso7816_config)
> > > +		return -ENOIOCTLCMD;  
> > 
> > Why this error value?
> >   
> 
> It was a mimic of RS485.

Which is what you want - it means the upper tty layer knows to offer the
ioctl to other places and then return appropriately.

Alan