On Wednesday 16 July 2014 18:35:33 Jassi Brar wrote: > On 16 July 2014 18:15, Arnd Bergmann <arnd@xxxxxxxx> wrote: > > On Wednesday 16 July 2014 18:07:04 Jassi Brar wrote: > >> On 16 July 2014 15:46, Arnd Bergmann <arnd@xxxxxxxx> wrote: > >> > On Wednesday 16 July 2014 10:40:19 Sudeep Holla wrote: > >> >> > + > >> >> > +Required property: > >> >> > +- mbox: List of phandle and mailbox channel specifier. > >> >> > + > >> >> > +- mbox-names: List of identifier strings for each mailbox channel > >> >> > + required by the client. > >> >> > + > >> >> > >> >> IMO the mailbox names are more associated with the controller channels/ > >> >> mailbox rather than the clients using it. Does it make sense to move > >> >> this under controller. It also avoid each client replicating the names. > >> > > >> > I think it would be best to just make the mbox-names property optional, > >> > like we have for other subsystems. > >> > > >> A very similar subsystem - DMAEngine also has 'dma-names' as a > >> required property. > >> > >> If a client is assigned only 1 mbox in DT, we can do without > >> mbox-names. But I am not sure what to do if a client needs two or more > >> differently capable mboxes? Simply allocating in order of mbox request > >> doesn't seem very robust. > > > > Traditionally, these things (regs, interrupts, ...) are just accessed > > by index. The reason why dmaengine requires the name is that some machines > > can use multiple DMA engine devices attached to the same request line, > > so the dmaengine subsystem can pick any of them that has a matching > > name. > And also, I think, when a client needs 2 different dma channels, say > for RX and TX each. The api can't assign the first channel specified > in 'dmas' property to the first channel request that comes to it, > unless we assume client driver always requests dma channels in the > order written in its DT node. And this is the main reason I see for > having mbox-names property. Most subsystems require passing an explicit index in this case. > If we make mbox-names optional, do we assume client driver must > request mbox in the order specified in its DT node? Correct. Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
