On 16 July 2014 21:39, Suman Anna <s-anna@xxxxxx> wrote: > Hi, > > On 07/16/2014 09:18 AM, Jassi Brar wrote: >> 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. > > I like this too, especially given that the framework uses this only to > retrieve the index. The mbox_client structure currently requires the > chan_name to be filled in, which means both the client driver and the > framework end up having to parse the property. > Yeah let us discourage the use of mbox-names. > While we are at this, how about we change the property name from "mbox" > to a plural-form "mboxes" to be inline with gpios, dmas etc. > OK, will change mbox to mboxes. -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
