netdev - Re: [PATCH 11/15] RDMA/hbl: add habanalabs RDMA driver

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Message-ID: <20240716134013.GF14050@ziepe.ca>
Date: Tue, 16 Jul 2024 10:40:13 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Omer Shpigelman <oshpigelman@...ana.ai>
Cc: Leon Romanovsky <leon@...nel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"ogabbay@...nel.org" <ogabbay@...nel.org>,
	Zvika Yehudai <zyehudai@...ana.ai>
Subject: Re: [PATCH 11/15] RDMA/hbl: add habanalabs RDMA driver

On Sun, Jul 14, 2024 at 10:18:12AM +0000, Omer Shpigelman wrote:
> On 7/12/24 16:08, Jason Gunthorpe wrote:
> > [You don't often get email from jgg@...pe.ca. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> > 
> > On Fri, Jun 28, 2024 at 10:24:32AM +0000, Omer Shpigelman wrote:
> > 
> >> We need the core driver to access the IB driver (and to the ETH driver as
> >> well). As you wrote, we can't use exported symbols from our IB driver nor
> >> rely on function pointers, but what about providing the core driver an ops
> >> structure? meaning exporting a register function from the core driver that
> >> should be called by the IB driver during auxiliary device probe.
> >> Something like:
> >>
> >> int hbl_cn_register_ib_aux_dev(struct auxiliary_device *adev,
> >>                              struct hbl_ib_ops *ops)
> >> {
> >> ...
> >> }
> >> EXPORT_SYMBOL(hbl_cn_register_ib_aux_dev);
> > 
> > Definately do not do some kind of double-register like this.
> > 
> > The auxiliary_device scheme can already be extended to provide ops for
> > each sub device.
> > 
> > Like
> > 
> > struct habana_driver {
> >    struct auxiliary_driver base;
> >    const struct habana_ops *ops;
> > };
> > 
> > If the ops are justified or not is a different question.
> > 
> 
> Well, I suggested this double-register option because I got a comment that
> the design pattern of embedded ops structure shouldn't be used.
> So I'm confused now...

Yeah, don't stick ops in random places, but the device_driver is the
right place.

> I'll look into the option of using notifier chains in this case, although
> as I saw it, the notifier chains are more suitable for broadcast updates
> where the updater is not necessarily aware of the identity nor the number
> of the subscribers. 

Yes, that is right.

Jason