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.krogerus@xxxxxxxxxxxxxxx> > > > +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 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
