On 05/16/2012 12:46 PM, Stephen Warren wrote: > On 05/16/2012 11:37 AM, Jon Hunter wrote: >> >> >> On 05/16/2012 12:24 PM, Jassi Brar wrote: >>> On 16 May 2012 22:42, Jon Hunter <jon-hunter@xxxxxx> wrote: >>> >>>>>> What is still unclear to me, is if you use this token approach how >>>>>> readable is the device-tree? For example, if you have a client that can >>>>>> use one of two dmac and for each dmac the request/channel number is >>>>>> different, then by using a global token how can I determine what the >>>>>> options available for this client are? >>>>>> >>>>> Simple - you/client need not know about any option at all :) >>>>> >>>>> Client driver would simply request some channel and if it >>>>> doesn't get it, it bails out. >>>>> >>>>> It would be the DMACs' DT node that would contain that info. >>>> >>>> Yes, but what if I am doing some custom application and want to modify >>>> the mapping that is being used? So I just wanted to make sure it is easy >>>> to understand assuming that you understand what your h/w is capable of. >>>> >>> Any scenario when a client would want to choose which dma controller >>> it runs on? >>> >>> Because when we say a client could be provided a channel on any of the >>> two given dmacs, it implies that the client wouldn't feel any difference. >> >> That's not my point. I am saying for some reason, maybe QoS, _I_ want to >> specify which mapping used. I am the one that knows how the h/w is being >> used and _I_ want to customise the dma/channel mapping in the DT, such >> that when the client asks for it I know what it is getting. Yes to the >> client, it does not care, but I do. > > If you really need to do that, you could always just lie in the DT node > of the DMA controllers you don't want to use, and omit the entry for the > DMA client(s) you don't want to use it. Exactly. The point I am trying to make, is that whatever binding we have it needs to be intuitive such that someone who knows the hardware could customise by removing entries, etc. This is probably a mute point now that we are not using the token scheme, but I wanted to be clear that I could see people customising the stock dev-trees in the kernel for their particular application. That's all. Jon -- 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
