Hi, Oliver Neukum <oneukum@xxxxxxxx> writes: > On Wed, 2016-02-17 at 09:58 +0200, Heikki Krogerus wrote: >> On Tue, Feb 16, 2016 at 02:39:47PM +0100, Oliver Neukum wrote: >> > On Tue, 2016-02-16 at 11:22 +0200, Heikki Krogerus wrote: >> > > > That question has not been answered. It would be awkward for the OS >> > > > to find itself in the slave role, which it is ill equipped for. So >> > > > the data role should be switched before the new device is announced >> > > > to user space. How is that handled? >> > > >> > > In the class driver, once we add support for preselecting the role, >> > > when the connection happens we compare the initial role to the >> > > preselected one and execute swap if it differs. Only after that we >> > > notify userspace. >> > >> > Yes, but we need an API. We can't keep adding to it. So if that >> > is to be supported, it needs to be defined now. >> >> When you say API, do you mean the API the class provides to the >> drivers? Or did you mean ABI which would be the sysfs in this case? > > The API to user space. That is the point. We cannot break user space. > Once this sysfs API is upstream we are stuck with it. yeah, in fact I have been wondering if sysfs is the best interface to userspace. I talked with Heikki a few days back about this; I was wondering if something like what the NFC folks did with netlink would be better here. -- balbi
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