Re: [openmcapi-dev] Re: [RFC] Inter-processor Mailboxes Drivers

On 02/15/2011 10:22 PM, Hiroshi DOYU wrote:

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

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On 02/15/2011 01:58 PM, Meador Inge wrote:

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On 02/14/2011 04:01 AM, Jamie Iles wrote:

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On Fri, Feb 11, 2011 at 03:19:51PM -0600, Meador Inge wrote:

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      1. Hardware specific bits somewhere under '.../arch/*'.  =

Drivers

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         for the MPIC message registers on Power and OMAP4 =

mailboxes,

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for
         example.
      2. A higher level driver under '.../drivers/mailbox/*'.  =

That the

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         pieces in (1) would register with.  This piece would =

expose the

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         main kernel API.
      3. Userspace interfaces for accessing the mailboxes.  A
         '/dev/mailbox1', '/dev/mailbox2', etc... mapping, for =

example.

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How about using virtio for all of this and having the mailbox as a
notification/message passing driver for the virtio backend?  There =

are

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already virtio console and network drivers that could be useful for =

the

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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.

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To be honest, I am not that familiar with 'virtio', but I will take =

a

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look.  Thanks for the pointer.  Maybe Hollis can speak to this idea =

more.

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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 think the proposal is to implement a virtio link using the OMAP=20
mailboxes as the interrupt mechanism, and shared memory to carry the=20
data and descriptor rings.

Hollis Blanchard
Mentor Graphics, Embedded Systems Division