netdev - RE: [RFC 01/20] ice: Initialize and register multi-function device to provide RDMA

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Message-ID: <2B0E3F215D1AB84DA946C8BEE234CCC97B2B1A28@ORSMSX101.amr.corp.intel.com>
Date:   Fri, 27 Sep 2019 18:03:51 +0000
From:   "Ertman, David M" <david.m.ertman@...el.com>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>
CC:     "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
        "jgg@...lanox.com" <jgg@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "dledford@...hat.com" <dledford@...hat.com>
Subject: RE: [RFC 01/20] ice: Initialize and register multi-function device
 to provide RDMA

> -----Original Message-----
> From: gregkh@...uxfoundation.org [mailto:gregkh@...uxfoundation.org]
> Sent: Thursday, September 26, 2019 10:13 PM
> To: Nguyen, Anthony L <anthony.l.nguyen@...el.com>
> Cc: Kirsher, Jeffrey T <jeffrey.t.kirsher@...el.com>; jgg@...lanox.com;
> netdev@...r.kernel.org; linux-rdma@...r.kernel.org; dledford@...hat.com;
> Ertman, David M <david.m.ertman@...el.com>
> Subject: Re: [RFC 01/20] ice: Initialize and register multi-function device to
> provide RDMA
> 
> On Thu, Sep 26, 2019 at 11:39:22PM +0000, Nguyen, Anthony L wrote:
> > On Thu, 2019-09-26 at 20:05 +0200, Greg KH wrote:
> > > On Thu, Sep 26, 2019 at 09:45:00AM -0700, Jeff Kirsher wrote:
> > > > From: Tony Nguyen <anthony.l.nguyen@...el.com>
> > > >
> > > > The RDMA block does not advertise on the PCI bus or any other bus.
> > >
> > > Huh?  How do you "know" where it is then?  Isn't is usually assigned
> > > to a PCI device?
> >
> > The RDMA block does not have its own PCI function so it must register
> > and interact with the ice driver.
> 
> So the "ice driver" is the real thing controlling the pci device?  How does it
> "know" about the RDMA block?
> 
> thanks,
> 
> greg k-h

The ICE driver loads and registers to control the PCI device.  It then
creates an MFD device with the name 'ice_rdma'. The device data provided to
the MFD subsystem by the ICE driver is the struct iidc_peer_dev which
contains all of the relevant information that the IRDMA peer will need
to access this PF's IIDC API callbacks

The IRDMA driver loads as a software only driver, and then registers a MFD
function driver that takes ownership of MFD devices named 'ice_rdma'.
This causes the platform bus to perform a matching between ICE's MFD device
and IRDMA's driver.  Then the patform bus will call the IRDMA's IIDC probe
function.  This probe provides the device data to IRDMA.

Dave E