[RFC] Inter-processor Mailboxes Drivers

Hi Meador,

From: ext Meador Inge <redacted>
Subject: [RFC] Inter-processor Mailboxes Drivers
Date: Fri, 11 Feb 2011 15:19:51 -0600

Hi All,

I am currently working on building AMP systems using OpenMCAPI
(https://bitbucket.org/hollisb/openmcapi/wiki/Home) as the
inter-processor communication mechanism.  With OpenMCAPI we, of
course,
need a way to send messages to various cores.  On some Freescale PPC
platforms (e.g. P1022DS, MPC8572DS), we have been using message
registers to do this work.  Recently, I was looking at the OMAP4
mailboxes to gear up for moving into ARM based platforms.

With that, I noticed 'arch/arm/plat-omap/mailbox.c'.  This is very
specific to the OMAP4 boards.  I am looking at designing a new set of
drivers to expose a mailbox service to userspace that will be used
for inter-processor communication.  This would entail the traditional
generic/specific driver split:

    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.

Now I have the following questions:

    1. Do others see value in this?

Yes.

I discussed this with TI(Hari) long time ago, but it didn't proceed
with some reason, not techinical one.

    2. Does something like this already exist?
    3. Is someone else already working on this?

Any feedback will be greatly appreciated.

Now the basic concpet can be devided into 3 parts, (1)HW dependent,
(2) generic driver, (3) character device interface. I guess that it
might be good to have one _pseudo_ H/W instance, then easier for
verification without real H/W and firmwares, across multiplatforms.