On Monday 21 May 2012, Stephen Warren wrote: > > > > The point with the direction was that it covers most cases and makes > > them rather simple, while for the rare case where you need more than > > two channels, you just use the otherwise optional named interface > > rather than the numbered one. My feeling is that this also makes a > > lot of sense at the driver API level: most dirvers just ask for the > > read and write channels using a very simple interface, and those drivers > > that have more than two will want to name them anyway. > > How are you thinking of representing the direction in DT - as part of > the DMA request specifier, so in a DMAC-specific way? > > If so, that seems a little odd; you have to request a DMA channel for > "TX", but then end up having the common code check all the entries in > the dmas property since it can't know which are TX, and then have the > wrong ones almost accidentally fail, since the DMAC will then determine > that it can't support TX on the RX DMA request IDs. I think the direction must be encoded in a way that does not depend on the binding for the specific controller. There are two ways I can see how we might do it: 1. have separate property names for tx and rx channels, and probably one for combined rx/tx channels 2. define the second cell in each channel specifier to be the direction in a predefined format, followed by the other (controller specific) attributes, if any. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
