Am Freitag, 4. Dezember 2009 17:50:40 schrieb Greg KH:
> On Fri, Dec 04, 2009 at 05:16:19PM +0100, Oliver Neukum wrote:
> > Am Freitag, 4. Dezember 2009 17:06:57 schrieb Alan Stern:
> > > Oliver:
> > >
> > > We don't have to worry about the device structure being deallocated
> > > while the routine is running. If that happens it's a bug in the
> > > caller: improper refcounting.
> >
> >
> > That raises two points
> >
> > 1. am I supposed to get a reference just so that I can use dev_err?
>
> No, you should already have a reference on the device when doing the
> call, right?
No, why? Consider this:
int write(...)
{
...
mutex_lock(&instance->lock);
if (instance->disconnected) {
dev_dbg(instance->dev,"writing to disconnected device");
rv = -ENODEV;
} else {
res = usb_submit_urb(...);
rv = res < 0 ? -EIO : count;
}
mutex_unlock(&instance->lock);
return rv;
}
void disconnect(...)
{
...
mutex_lock(&instance->lock);
instance->disconnected = 1;
usb_kill_urb(...);
usb_kill_urb(...);
mutex_unlock(&instance->lock);
}
This would be perfectly valid code without any references taken save
for the pesky dev_dbg()
Regards
Oliver
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