On 04/10/17 12:24, Arnd Bergmann wrote: > On Thu, Sep 28, 2017 at 3:11 PM, Sudeep Holla <sudeep.holla@xxxxxxx> wrote: >> Some of the mailbox controller expects controller specific data in order >> to implement simple doorbell mechanism as expected by SCMI specification. >> >> This patch creates a shim layer to abstract the mailbox interface so >> that it can support any mailbox controller. It also provides default >> implementation which maps to standard mailbox client APIs, so that >> controllers implementing doorbell mechanism need not require any >> additional layer. >> >> Cc: Arnd Bergmann <arnd@xxxxxxxx> >> Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx> > > Another level? Now we have three levels of stacked mailboxes, with > the highest level being the combined mailbox/memory, then the shim, > and below it the hardware mailbox. > > Can you try to come up with a way to do this with fewer abstractions? > I completely agree with you. I was against this but Jassi recommended this. I just wanted this SCMI to work with mailbox controllers that support simple doorbell mechanism as specified in the specification but Jassi disagrees with that. > Maybe you could assume that the mailbox itself can take variable-length > data packets, and then use the shim here for those that require > something else? > As per SCMI specification, we pass all the data in shared memory and it just expects to use a simple doorbell feature from hardware mailbox controllers. It's done that way intentionally to avoid dependency on h/w and we for sure will have variety of it and that defeats the purpose of this standard specification. Also, I have added shim only for specific controllers that need them. E.g. ARM MHU as Jassi disagreed to add doorbell mechanism to that. mbox_if provides default implementation that just calls direct mailbox APIs. -- Regards, Sudeep -- 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
