Re: [PATCH] cdc-acm: some enhancement on acm delayed write

[Johan Hovold <jhovold@gmail.com>]

> > > If I see this correctly, then ASYNCB_INITIALIZED is cleared in
> > > tty_port_close() we is called from acm_tty_close(). Thus it should
> > > be enough to make sure that the device is resumed at the beginning
> > > of acm_tty_close() and acm_resume() will do the job automatically.
> > > What do you think?
> > 
> > But the device should already be about to be resumed, right? If the port
> 
> Yes.
> 
> > is closed fast enough that resume hasn't had time to run before
> > shutdown is called I think the right thing to do is simply to discard
> > the delayed bytes (in shutdown).
> 
> I think if we said we have transmitted then we should do so.

We haven't made any such promises -- only that we've buffered the data.
Just like any write urb can be cancelled at close / shutdown before
having been transmitted.

The user needs to use closing_wait or drain_delay to give the buffers a
chance to empty. If not used at all, or we get a time out, then the data
should be discarded.

Johan