On Fri, 12 Jun 2009, Hans Verkuil wrote: > > 1. it is very unusual that the board designer has to mandate what signal > > polarity has to be used - only when there's additional logic between the > > capture device and the host. So, we shouldn't overload all boards with > > this information. Board-code authors will be grateful to us! > > I talked to my colleague who actually designs boards like that about what > he would prefer. His opinion is that he wants to set this himself, rather > than leave it as the result of a software negotiation. It simplifies > verification and debugging the hardware, and in addition there may be > cases where subtle timing differences between e.g. sampling on a falling > edge vs rising edge can actually become an important factor, particularly > on high frequencies. I'd say this is different. You're talking about cases where you _want_ to be able to configure it explicitly, I am saying you do not have to _force_ all to do this. Now, this selection only makes sense if both are configurable, right? In this case, e.g., pxa270 driver does support platform-specified preference. So, if both the host and the client can configure either polarity in the software you _can_ still specify the preferred one in platform data and it will be used. I think, the ability to specify inverters and the preferred polarity should cover all possible cases. Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/ -- 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
