Am Dienstag, 8. Mai 2007 23:59 schrieb Alan Stern:
> On Tue, 8 May 2007, Oliver Neukum wrote:
>
> > Am Dienstag, 8. Mai 2007 20:59 schrieb Alan Stern:
> > > > 2. I would prefer to have exclusion between open and reset, too.
> > >
> > > Why? I can understand wanting exclusion between read/write and reset.
> > > But there's no obvious reason to make open and reset exclusive.
> >
> > I don't think we'd want mutual exclusion in these cases. In fact read/write
> > should fail in case a device is being reset or has been reseted.
>
> You probably can't prevent ongoing reads and writes from failing. But you
> can delay new reads/writes until the reset is finished, giving them a
> fighting chance of succeeding.
I don't think we can let them succeed in the common case. Many devices,
eg. modems, printers, ..., have settings which a driver cannot restore, as it
does not understand the io.
In all these cases you have to tell user space that the device has been
reset, which means that io has to return an error code.
When possible I want to avoid this scenario by delay.
Regards
Oliver
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