On 16 July 2014 19:38, Arnd Bergmann <arnd@xxxxxxxx> wrote: > 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. > Sounds great. Thanks Jassi -- 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
