netdev - RE: [PATCH 07/22] RDMA/irdma: Register an auxiliary driver and implement private channel OPs

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Date:   Tue, 2 Feb 2021 00:40:28 +0000
From:   "Saleem, Shiraz" <shiraz.saleem@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     Leon Romanovsky <leon@...nel.org>,
        "dledford@...hat.com" <dledford@...hat.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Ertman, David M" <david.m.ertman@...el.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        "Ismail, Mustafa" <mustafa.ismail@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
        "Patil, Kiran" <kiran.patil@...el.com>
Subject: RE: [PATCH 07/22] RDMA/irdma: Register an auxiliary driver and
 implement private channel OPs

> Subject: Re: [PATCH 07/22] RDMA/irdma: Register an auxiliary driver and
> implement private channel OPs
> 
> On Sat, Jan 30, 2021 at 01:19:36AM +0000, Saleem, Shiraz wrote:
> > > Subject: Re: [PATCH 07/22] RDMA/irdma: Register an auxiliary driver
> > > and implement private channel OPs
> > >
> > > On Wed, Jan 27, 2021 at 07:16:41PM -0400, Jason Gunthorpe wrote:
> > > > On Wed, Jan 27, 2021 at 10:17:56PM +0000, Saleem, Shiraz wrote:
> > > >
> > > > > Even with another core PCI driver, there still needs to be
> > > > > private communication channel between the aux rdma driver and
> > > > > this PCI driver to pass things like QoS updates.
> > > >
> > > > Data pushed from the core driver to its aux drivers should either
> > > > be done through new callbacks in a struct device_driver or by
> > > > having a notifier chain scheme from the core driver.
> > >
> > > Right, and internal to driver/core device_lock will protect from
> > > parallel probe/remove and PCI flows.
> > >
> >
> > OK. We will hold the device_lock while issuing the .ops callbacks from core
> driver.
> > This should solve our synchronization issue.
> >
> > There have been a few discussions in this thread. And I would like to
> > be clear on what to do.
> >
> > So we will,
> >
> > 1. Remove .open/.close, .peer_register/.peer_unregister 2. Protect ops
> > callbacks issued from core driver to the aux driver with device_lock
> 
> A notifier chain is probably better, honestly.
> 
> Especially since you don't want to split the netdev side, a notifier chain can be
> used by both cases equally.
> 

The device_lock seems to be a simple solution to this synchronization problem.
May I ask what makes the notifier scheme better to solve this?

Also, are you suggesting we rid all the iidc_peer_op callbacks used for 'ice' to 'irdma' driver
communication and replace with events generated by ice driver which will be received
by subscriber irdma? Or just some specific events to solve this synchronization problem?
Sorry I am confused.

Shiraz