On Thu, Dec 05, 2013 at 04:37:39PM +0200, Tomi Valkeinen wrote: > On 2013-11-27 12:54, Thierry Reding wrote: > > >> I am not sure about hardwiring devices to virtual channels. > >> There could be devices which uses more than one virtual channel, > >> in fact exynos-drm docs suggests that such hardware exists. > > > > In that case, why not make them two logically separate devices within > > the kernel. We need the channel number so that the device can be > > addressed in the first place, so I don't see what's wrong with using > > that number in the device's name. > > > > The whole point of this patch is to add MIPI DSI bus infrastructure, and > > the virtual channel is one of the fundamental aspects of that bus, so I > > think we need to make it an integral part of the implementation. > > (I speak here more in the context of OMAP display subsystem and CDF, and > this might not be totally applicable to DRM). > > In my opinion, DSI shouldn't be though of in the same way as other buses. > > In most of the cases, there's just one DSI peripheral connected. This > peripheral may answer to multiple DSI VC IDs, though. I don't like the > idea of having to split one device driver into multiple drivers, just to > manage multiple DSI VC IDs.
If they respond to multiple VCs, then I suppose they would be logically separate devices, even if only a single physical device. What would be the point of addressing them individually if they are just the same device? > In some rare cases (I've never seen one in production) there may be a > DSI hub, and one or two DSI peripherals behind it. But the hub is not > really a hub, but a router, and the router requires configuration. The > case here is not really one DSI bus with two or more peripherals, but > two or more independent 1-to-1 DSI buses.
