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

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Date:   Mon, 1 Feb 2021 15:18:05 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     "Saleem, Shiraz" <shiraz.saleem@...el.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>
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.

Jason