On Thu, 2012-07-26 at 10:53 -0500, Jon Hunter wrote: > On 07/26/2012 06:28 AM, Vinod Koul wrote: > > On Thu, 2012-07-26 at 07:14 +0000, Arnd Bergmann wrote: > >> On Thursday 26 July 2012, Vinod Koul wrote: > >>>>> But from a client POV it makes sense as with the given direction you > >>>>> would need a specific request line for a channel. So this is right. > >>>>> But direction is something I don't expect to be used for "give me a > >>>>> channel" > >>>> > >>>> Ok. The thought was that the user would have the following means of > >>>> requesting a channel ... > >>>> > >>>> 1. By name > >>> Bare name maynot be enough. In a dmac we have many channels which one to > >>> choose? > >> The name is what is associated with the property in the client device > >> node, which describes everything the dmac driver needs to know. > >> If the dmac needs to pick a specific channel, it can find out from the > >> "dmas" property in combination with that name. If it is allowed to > >> pick any channel, it doesn't need to bother. > > dmac doesn't pick a channel. They don't come into picture till dmaengine > > and client have agreed on channel. And then channel callback in invoked, > > still it doesn't know which client. > > I think what Arnd meant was that dmaengine (not the dmac) would use the > DT node and name information to extract the dma mapping information from > the device tree and provide a channel back to the client. So yes the > dmac is not involved here. Ok good that was main concern :) > > By the way, when I said "by name" above (and probably this was not > clear) but it should have been "DT node and name". So really a channel > is requested by ... > > 1. DT node and a name > 2. DT node and a filter parameter (flags) > 3. DT node, a name and a filter parameter (flags) > > The DT node points us to the specific device in the DT, say an MMC node, > and the MMC node then contains the DMA mapping info. The device node may > have the mapping information have one or more DMA requests/channels and > so then the name and/or flags is used to determine which the client needs. > > Sorry hope that this is a little clearer. It is... -- ~Vinod -- 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
