[RFC] Inter-processor Mailboxes Drivers

[Hiroshi DOYU]

From: "ext Blanchard, Hollis" <Hollis_Blanchard at mentor.com>
Subject: Re: [RFC] Inter-processor Mailboxes Drivers
Date: Tue, 15 Feb 2011 15:38:25 -0800

> On 02/15/2011 01:58 PM, Meador Inge wrote:
>> On 02/14/2011 04:01 AM, Jamie Iles wrote:
>>> On Fri, Feb 11, 2011 at 03:19:51PM -0600, Meador Inge wrote:
>>>>      1. Hardware specific bits somewhere under '.../arch/*'.  Drivers
>>>>         for the MPIC message registers on Power and OMAP4 mailboxes, 
>>>> for
>>>>         example.
>>>>      2. A higher level driver under '.../drivers/mailbox/*'.  That the
>>>>         pieces in (1) would register with.  This piece would expose the
>>>>         main kernel API.
>>>>      3. Userspace interfaces for accessing the mailboxes.  A
>>>>         '/dev/mailbox1', '/dev/mailbox2', etc... mapping, for example.
>>>
>>> How about using virtio for all of this and having the mailbox as a
>>> notification/message passing driver for the virtio backend?  There are
>>> already virtio console and network drivers that could be useful for the
>>> userspace part of it.  drivers/virtio/virtio_ring.c might be a good
>>> starting point if you thought there was some mileage in this approach.
>>
>> To be honest, I am not that familiar with 'virtio', but I will take a 
>> look.  Thanks for the pointer.  Maybe Hollis can speak to this idea more.
> My opinion is that virtio is (over?) complicated.

Considering the case of omap mailbox H/W, it is just a simple one way
4 slot x 32bit H/W FIFO, I also may think that this may be a bit too
much...

> I've looked into it in the past, and I'm definitely open to using it if 
> somebody can demonstrate how easy it is, but adopting it wouldn't have 
> helped OpenMCAPI with our use cases, and would have incurred extra pain, 
> so we didn't.
> 
> Hollis Blanchard
> Mentor Graphics, Embedded Systems Division
>