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. Or, does this topic assume an otg controller handles 2 EHCI controllers? I'm not sure such environment actually exists. > > 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. 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. Best regards, Yoshihiro Shimoda > Alan Stern -- 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
