Re: [RFC 1/6] mailbox: add core framework

[Josh Cartwright <joshc@codeaurora.org>]

On Mon, Feb 10, 2014 at 11:52:05AM -0600, Rob Herring wrote:
> On Mon, Feb 10, 2014 at 8:11 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > On Friday 07 February 2014 16:50:14 Courtney Cavin wrote:
[..]
> >> +int mbox_channel_notify(struct mbox_channel *chan,
> >> +             const void *data, unsigned int len)
> >> +{
> >> +     return atomic_notifier_call_chain(&chan->notifier, len, (void *)data);
> >> +}
> >> +EXPORT_SYMBOL(mbox_channel_notify);
> >
> > What is the reason to use a notifier chain here? Isn't a simple
> > callback function pointer enough? I would expect that each mailbox
> > can have exactly one consumer, not multiple ones.
> 
> It probably can be a callback, but there can be multiple consumers. It
> was only a notifier on the pl320 as there was no framework at the time
> and to avoid creating custom interfaces between drivers. On highbank
> for example, we can asynchronously receive the events for temperature
> change, power off, and reset. So either there needs to be an event
> demux somewhere or callbacks have to return whether they handled an
> event or not.

I'm not familiar with highbank IPC, but with these requirements should
the mailbox core even bother with asynchronous notifier chain?  It
sounds like a better fit might be for the mailbox core to implement a
proper adapter-specific irqdomain and used a chained irq handler to
demux (or have consumers request with IRQF_SHARED in the shared case).

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