Re: [patch]usb_serial_driver insufficient for clean disconnect handling

Am Donnerstag, 15. März 2007 23:10 schrieb Greg KH:
> On Thu, Mar 15, 2007 at 01:59:30PM +0100, Oliver Neukum wrote:
> > Hi,
> > 
> > it seems to me that for several usb serial drivers it is currently
> > impossible to cleanly handle disconnect, because usb_serial_driver
> > lacks a needed method.
> > 
> > As we often discussed, before a disconnect handler may return, it has
> > to finish all IO to the device. That means that usb_kill_urb() has to be
> > called on all URBs that might be active.
> > The serial driver does kill all standard URBs (bulk/interrupt in/out)
> > but it does not and indeed cannot deal with any private URBs (eg.
> > control URBs as in mos7720/mos7840).
> > The shutdown() method is unable to do the job because it can be
> > delayed if additional references to the port exist.
> > 
> > To allow killing them in time I propose this additional method for
> > usb_serial_driver.
> 
> This looks good to me, thanks for doing this.  I missed this change when
> we switched to the driver model.
> 
> However, shouldn't we just be calling "shutdown" here instead?  Lots of

Currently the locking is not good enough to call shutdown() so early.
It could be strengthened. Make your choice. I can and will do it
either way. Just the current state of affairs is bad.

> drivers do their tear-down in that function.  Unless you are going to
> start converting drivers to use this new callback?

A model with one callback having the clear meaning "stop all IO"
and a second callback "free all memory" has its merits.

But this code is your design. Tell me what you like best and I'll do
it.

	Regards
		Oliver

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