On Wednesday 16 July 2014 18:42:22 Jassi Brar wrote: > On 16 July 2014 18:39, Arnd Bergmann <arnd@xxxxxxxx> wrote: > > 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. > > > OK. So how about we drop mbox-names altogether and expect client > driver to simply provide an index of the mbox needed? That would be fine with me, but I think a lot of people like the idea of identifying things by name, and are used to that from the other subsystems. Maybe you can leave the mbox-names property defined as 'optional' in the generic mbox binding but remove the code in Linux? That way we can always put it back at a later point without changing the binding in an incompatible way. Individual mailbox clients can mandate specific strings. 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
