On 10 November 2014 18:27, Ashwin Chaugule <ashwin.chaugule@xxxxxxxxxx> wrote: > On 9 November 2014 23:13, Jassi Brar <jaswinder.singh@xxxxxxxxxx> wrote: >> >>>>> based on the discussions that followed since, we decided that its best >>>>> to add a separate PCC lookup and registration API. The main reason >>>>> being, we dont have a way to list all mbox providers in ACPI in a way >>>>> that DT does. e.g. in DT, the client->dev is used to look up mbox >>>>> controllers. In ACPI, a client cant specify which mbox controllers to >>>>> associate with, if it can attach to multiple. With the PCC specific >>>>> API, if the client calls it, the controller knows where to look, >>>>> because that lookup is PCC specific. >>>>> >>>>> In your patch, the assumption that PCC is the only ACPI mbox provider, >>>>> maybe true today, but that can change anytime. >>>>> >>>> Please read my patch again, we can have ACPI as well as DT populated >>>> clients. All that you intend to do with this patch can be done there >>>> and _without_ adding new apis. >>> >>> Read it again. Not arguing that your patch wont work for DT and ACPI, >>> but your assumption that ACPI supports PCC as the only mbox >>> controller, may not hold true. The global_xlate function will work >>> fine for PCC, but may not work for other ACPI (non-DT) mbox >>> controllers. Using the signature field/index byte works only for PCC. >>> We've already been through this discussion with Mark and Arnd and we >>> came up with the PCC API. >>> >> Please read it yet again. There is no assumption that PCC is the only >> mbox in ACPI (though I think that is very likely). The function and >> its argument are both named _global_. 'Signature' is mentioned only as >> an example in case of PCC. The PCC controller driver could expect the >> global_id to be 'signature' of the subspace, similarly another non-DT >> mailbox controller driver will expect its own different 'signature' >> (say 0xdead0000 | id_16bits). In the patch I submitted we try >> .global_xlate() of all such mboxes and only one, which finds its >> id-space specified, will return a channel. >> >> Ideally, global-id space isn't very clean, but for mailbox we anyway >> have to have a direct understanding between controller and client >> drivers. So having global IDs is a great tradeoff if we avoid messing >> up the api. > > How is this different than expecting the client to pass a string name > of the mbox controller it wants? > Global-ID is ugly, string matching is uglier. String matching requires changes to client and provider structures as opposed to simple numerical comparison to find a suitable channel. -Jassi -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
