On Tue, 2016-08-30 at 13:04 +0300, Heikki Krogerus wrote:
> On Tue, Aug 30, 2016 at 11:32:01AM +0200, Oliver Neukum wrote:
Hi,
> > On Mon, 2016-08-29 at 15:36 +0300, Heikki Krogerus wrote:
> > > +What: /sys/class/typec/<port>/current_data_role
> > > +Date: June 2016
> > > +Contact: Heikki Krogerus <heikki.kroge...@linux.intel.com>
> > > +Description:
> > > + The current USB data role the port is operating in.
> > > This
> > > + attribute can be used for requesting data role
> > > swapping on the
> > > + port. Swapping is only supported as an asynchronous
> > > operation
> > > + and requires polling of the attribute in order to know
> > > the
> > > + result, so successful write operation does not mean
> > > successful
> > > + swap.
> > > +
> >
> > That is badly formulated. Does it mean that poll() or select()
> > can be used or does the value need to be repearedly read?
>
> Does polling not always mean poll/select?
No, it does not.
> > And how would you learn about an error?
>
> This is what I'm also really worried about. I'm now wondering did I
> give up too easily on this to Guenter in hope to move this thing
> forward. He said it's problematic to do these calls synchronously for
Error reporting does not require a synchronous operation. Reporting
it in the next read() or write() and making it pollable is perfectly
viable. It just must not be silently dropped.
Regards
Oliver
