On Thu, Apr 06, 2017 at 03:21:26PM +0200, Gerd Hoffmann wrote: > Hi, > > > The downside is that this is hard to specify formally, the same way we > > do other devices. Say we do that and point to a fixed version of the > > relevant Linux headers and the headers evolve and add or change > > something. Then we would either go change the spec to be in sync with > > the headers or build a compatibility layer in the implementation. > > Highly unlikely that the structs and ioctls in linux header change. > It's userspace <=> kernel abi. And even if they change some days it > would have to happen in a backward compatible way. So I think > documenting the ioctl structs we have today is reasonable. If new > ioctls for new device types show up we probably need a virtio feature > flag anyway to properly support them. > > Events (new key codes for example) are added now and then. So for them > we might continue referencing the include file with the codes instead of > copying them into the spec. > > > because evdev > > needs to maintain some reasonable backwards compatibility by itself so > > it's very unlikely that things would break. > > Yep. Unknown events can simply be ignored. And you can query the > device to figure which events (aka keys / axis / ...) are supported > (ioctl in evdev, config space in virtio). So that level of > compatibility is already taken care of, in both evdev and virtio. > > > > Let's assume linux gains ability to generate new events on top of old > > > ones. > > > Do you want to send both in all cases? > > > If you only send multitouch how do you handle old guests? > > > If you send both how does new guest know it should > > > ignore old events? > > > > I think that these are valid concerns but they need to be addressed at > > the evdev layer, not in virtio. > > Indeed. And I think multitouch is addressed by simply sending both. > Apps without multitouch support simply ignore the multitouch events. > Apps with multitouch support can figure this is a multitouch-capable > device and ignore the old events on those. > > cheers, > Gerd
Gerd is there a chance you could try and address whatever you think needs to be addressed and repost? Would be nice to have this in 1.1 and I think it's better to have an incomplete description than none. > > --------------------------------------------------------------------- > To unsubscribe, e-mail: virtio-dev-unsubscr...@lists.oasis-open.org > For additional commands, e-mail: virtio-dev-h...@lists.oasis-open.org --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscr...@lists.oasis-open.org For additional commands, e-mail: virtio-dev-h...@lists.oasis-open.org
