On Wednesday 23 February 2011 17:28:39 Hans Verkuil wrote: > On Wednesday, February 23, 2011 17:14:41 Laurent Pinchart wrote: > > On Wednesday 23 February 2011 17:02:57 Hans Verkuil wrote: [snip] > > > When you switch polarity for data/field/hsync/vsync signals on a simple > > > bus you just invert whether a 1 bit is output as high or low voltage. So > > > you just change the meaning of the bit. This does not matter for > > > signal integrity, since you obviously have to be able to sample both > > > low and high voltages. It is *when* you sample that can have a major > > > effect. > > > > When you switch the polarity you will likely have to sample on the > > opposite edge. If, for signal integrity reasons, you can only sample on > > a given edge, you will want to use a fixed polarity and not negotiate > > it. > > You are confusing clock polarity (which is relevant) with data, field, > hsync and vsync polarities which just invert the meaning of those pins. I was talking about clock polarity. Sorry for the confusion. > I wish I had a whiteboard to draw it, much easier to explain that way. > > > Given the very small number of parameters that are negotiated by > > soc-camera at the moment, I'm very much in favour of hardcoding all of > > them in platform data and just adding a g_interface_parms subdev > > operation. > > Just for the record: I have no problem with hardcoding these polarities. > After all, that was my original idea. But they can be negotiated as well. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
