linux-kernel - RE: [PATCH 0/3 v6] drivers/bus: Freescale Management Complex bus driver patch series

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Date:	Thu, 26 Feb 2015 20:32:53 +0000
From:	Stuart Yoder <stuart.yoder@...escale.com>
To:	Alexander Graf <agraf@...e.de>, "arnd@...db.de" <arnd@...db.de>
CC:	Jose Rivera <German.Rivera@...escale.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: RE: [PATCH 0/3 v6] drivers/bus: Freescale Management Complex bus
 driver patch series



> -----Original Message-----
> From: Alexander Graf [mailto:agraf@...e.de]
> Sent: Thursday, February 26, 2015 8:33 AM
> To: Yoder Stuart-B08248; arnd@...db.de
> Cc: Rivera Jose-B46482; linux-kernel@...r.kernel.org; gregkh@...uxfoundation.org
> Subject: Re: [PATCH 0/3 v6] drivers/bus: Freescale Management Complex bus driver patch series
> 
> 
> 
> On 27.01.15 15:35, Stuart Yoder wrote:
> > Hi Arnd/Alex,
> >
> > German has posted an example driver for the fsl-mc bus in his RFC
> > "[RFC PATCH 1/1] drivers/bus: fsl-mc object allocator driver".
> >
> > In addition I have made available the skeleton for a driver for
> > one of the objects/devices (crypto) that will be discovered on
> > the bus:
> >     https://github.com/stuyoder/linux
> >     branch: fsl-ms-bus
> >
> > ...it is not functional yet, but shows how a driver registers with
> > the bus, get's probed, performs initialization.
> 
> Ok, so if I grasp this correctly the idea is that we have a driver
> attaching to an individual device on the fsl-mc bus.

Yes.

> That driver then
> goes and allocates / blocks more devices from that bus as it initializes.

Yes, there are certain devices/objects on the bus that by themselves
are not standalone, functional devices.  An example is a "buffer pool".
Network interface drivers, crypto driver, decompression driver, etc need
one or more hardware buffer pools.  There is a buffer depletion interrupt
associated with the device.

The buffer pools itself binds to a resource allocation driver in
the kernel, which then can hand out buffer pools as required by
other drivers.

> Is that model always possible?

Yes, why would it not be?

> Which device would a NIC bind to for
> example?

Network interface / Ethernet driver requires some number
of buffer pools, plus a management complex portal device
(DPMCP) used for sending commands to manage the hardware.

> I merely want to make sure we're not running ourselves into a
> bad corner ;).

If we are, I would like to understand it. :)

Thanks,
Stuart
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