Re: [PATCH 8/11] usbserial: pl2303: Ports tty functions.

[Pete Zaitcev <zaitcev@redhat.com>]

On Fri, 2 Jun 2006 13:50:14 -0700, Greg KH <gregkh@suse.de> wrote:
> On Fri, Jun 02, 2006 at 12:03:14AM -0300, Luiz Fernando N.Capitulino wrote:

> >   2. The new pl2303's set_termios() can (still) sleep. Serial Core's
> >      documentation says that that method must not sleep, but I couldn't find
> >      where in the Serial Core code it's called in atomic context. So, is this
> >      still true? Isn't the Serial Core's documentation out of date?
> 
> If this is true then we should just stop the port right now, as the USB
> devices can not handle this.  They need to be able to sleep to
> accomplish this functionality.
> 
> Russell, is this a requirement of the serial layer?  Why?

Shouldn't it be all right to schedule the change at the moment of
that call and have it happen later? Resisting a temptation to abuse
keventd and schedule_work and using a tasklet may help with latency
enough to make this tolerable.

I'm sure that a generic mechanism to drive asynchronous usb_control_msg
is going to be required as well for this project. The pl2303 is just
lucky to avoid it.

-- Pete