On 12/05/16 07:00, Yoshihiro Shimoda wrote: > Hi, > >> From: Alan Stern >> Sent: Wednesday, May 11, 2016 11:47 PM >> >> On Wed, 11 May 2016, Roger Quadros wrote: >> >>>> What I mean is if you have 2 EHCI controllers with 2 companion >>>> controllers, don't you need to know which companion goes with which EHCI >>>> controller? Just like you do for the otg-controller property. >>>> >>> >>> That is a very good point. I'm not very sure and it seems that current code won't work >>> with multiple EHCI + companion instances. > > I may misunderstand this topic, but if I use the following environment, it works correctly. > > < My environment > > - an otg controller: Sets hcd-needs-companion. > - ehci0 and ohci0 and a function: They connect to the otg controller using "otg-controller" property. > - ehci1 and ohci1: No "otg-controller" property. > - ehci2 and ohci2: No "otg-controller" property. > > In this environment, all hosts works correctly. > Also I think if we have 2 otg controlelrs, it should be work because otg_dev instance differs. The topic is about more than one otg controllers and how to tie the right ehci and ohci to the correct otg_dev instance especially in cases where we can't depend on probe order. > Or, does this topic assume an otg controller handles 2 EHCI controllers? > I'm not sure such environment actually exists. No it is not about that. > >>> Alan, does USB core even know which EHCI and OHCI are linked to the same port >>> or the handoff is software transparent? >> >> The core knows. It doesn't use the information for a whole lot of >> things, but it does use it in a couple of places. Search for >> "companion" in core/hcd-pci.c and you'll see. > > Thank you for the information. I didn't know this code. > If my understanding is correct, the core/hcd-pci.c code will not be used by non-PCI devices. That is correct. > In other words, nobody sets "hcd->self.hs_companion" if we use such a device. > So, I will try to add such a code if needed. I think OTG core would have to rely on USB core in providing the right companion device, just like we rely on it for the primary vs shared HCD case. cheers, -roger -- 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
