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Date: Mon, 11 Mar 2024 08:32:03 -0700
From: Breno Leitao <leitao@debian.org>
To: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>, Leon Romanovsky <leon@kernel.org>,
	kuba@kernel.org, keescook@chromium.org,
	"open list:HFI1 DRIVER" <linux-rdma@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net-next] IB/hfi1: allocate dummy net_device dynamically
Message-ID: <Ze8j8yWyXCQtwcOJ@gmail.com>
References: <20240308182951.2137779-1-leitao@debian.org>
 <6460dd4b-9b65-49df-beaf-05412e42f706@cornelisnetworks.com>
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In-Reply-To: <6460dd4b-9b65-49df-beaf-05412e42f706@cornelisnetworks.com>

Hello Dennis,

On Mon, Mar 11, 2024 at 08:05:45AM -0400, Dennis Dalessandro wrote:
> On 3/8/24 1:29 PM, Breno Leitao wrote:
> > struct net_device shouldn't be embedded into any structure, instead,
> > the owner should use the priv space to embed their state into net_device.
> > 
> > Embedding net_device into structures prohibits the usage of flexible
> > arrays in the net_device structure. For more details, see the discussion
> > at [1].
> > 
> > Un-embed the net_device from struct iwl_trans_pcie by converting it
> > into a pointer. Then use the leverage alloc_netdev() to allocate the
> > net_device object at iwl_trans_pcie_alloc.
> 
> What does an Omni-Path Architecture driver from Cornelis Networks have to do
> with an Intel wireless driver?

That is an oversight. I will fix it in v2. Sorry about it.

> > The private data of net_device becomes a pointer for the struct
> > iwl_trans_pcie, so, it is easy to get back to the iwl_trans_pcie parent
> > given the net_device object.
> > 
> > [1] https://lore.kernel.org/all/20240229225910.79e224cf@kernel.org/
> > 
> > Signed-off-by: Breno Leitao <leitao@debian.org>
> > ---
> >  drivers/infiniband/hw/hfi1/netdev.h    | 2 +-
> >  drivers/infiniband/hw/hfi1/netdev_rx.c | 9 +++++++--
> >  2 files changed, 8 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/infiniband/hw/hfi1/netdev.h b/drivers/infiniband/hw/hfi1/netdev.h
> > index 8aa074670a9c..07c8f77c9181 100644
> > --- a/drivers/infiniband/hw/hfi1/netdev.h
> > +++ b/drivers/infiniband/hw/hfi1/netdev.h
> > @@ -49,7 +49,7 @@ struct hfi1_netdev_rxq {
> >   *		When 0 receive queues will be freed.
> >   */
> >  struct hfi1_netdev_rx {
> > -	struct net_device rx_napi;
> > +	struct net_device *rx_napi;
> >  	struct hfi1_devdata *dd;
> >  	struct hfi1_netdev_rxq *rxq;
> >  	int num_rx_q;
> > diff --git a/drivers/infiniband/hw/hfi1/netdev_rx.c b/drivers/infiniband/hw/hfi1/netdev_rx.c
> > index 720d4c85c9c9..5c26a69fa2bb 100644
> > --- a/drivers/infiniband/hw/hfi1/netdev_rx.c
> > +++ b/drivers/infiniband/hw/hfi1/netdev_rx.c
> > @@ -188,7 +188,7 @@ static int hfi1_netdev_rxq_init(struct hfi1_netdev_rx *rx)
> >  	int i;
> >  	int rc;
> >  	struct hfi1_devdata *dd = rx->dd;
> > -	struct net_device *dev = &rx->rx_napi;
> > +	struct net_device *dev = rx->rx_napi;
> >  
> >  	rx->num_rx_q = dd->num_netdev_contexts;
> >  	rx->rxq = kcalloc_node(rx->num_rx_q, sizeof(*rx->rxq),
> > @@ -360,7 +360,11 @@ int hfi1_alloc_rx(struct hfi1_devdata *dd)
> >  	if (!rx)
> >  		return -ENOMEM;
> >  	rx->dd = dd;
> > -	init_dummy_netdev(&rx->rx_napi);
> > +	rx->rx_napi = alloc_netdev(sizeof(struct iwl_trans_pcie *),
> > +				   "dummy", NET_NAME_UNKNOWN,
> > +				   init_dummy_netdev);
> 
> Again with the iwl stuff? Please do not stuff to the mailing list that doesn't
> even compile....
> 
>  CC [M]  drivers/infiniband/hw/hfi1/verbs.o
>   CC [M]  drivers/infiniband/hw/hfi1/verbs_txreq.o
>   CC [M]  drivers/infiniband/hw/hfi1/vnic_main.o
> In file included from ./include/net/sock.h:46,
>                  from ./include/linux/tcp.h:19,
>                  from ./include/linux/ipv6.h:95,
>                  from ./include/net/ipv6.h:12,
>                  from ./include/rdma/ib_verbs.h:25,
>                  from ./include/rdma/ib_hdrs.h:11,
>                  from drivers/infiniband/hw/hfi1/hfi.h:29,
>                  from drivers/infiniband/hw/hfi1/sdma.h:15,
>                  from drivers/infiniband/hw/hfi1/netdev_rx.c:11:
> drivers/infiniband/hw/hfi1/netdev_rx.c: In function ‘hfi1_alloc_rx’:
> drivers/infiniband/hw/hfi1/netdev_rx.c:365:36: error: passing argument 4 of
> ‘alloc_netdev_mqs’ from incompatible pointer type
> [-Werror=incompatible-pointer-types]
>   365 |                                    init_dummy_netdev);
>       |                                    ^~~~~~~~~~~~~~~~~
>       |                                    |
>       |                                    int (*)(struct net_device *)
> ./include/linux/netdevice.h:4632:63: note: in definition of macro ‘alloc_netdev’
>  4632 |         alloc_netdev_mqs(sizeof_priv, name, name_assign_type, setup, 1, 1)
>       |                                                               ^~~~~
> ./include/linux/netdevice.h:4629:44: note: expected ‘void (*)(struct net_device
> *)’ but argument is of type ‘int (*)(struct net_device *)’
>  4629 |                                     void (*setup)(struct net_device *),
>       |                                     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
>   CC [M]  drivers/infiniband/hw/hfi1/vnic_sdma.o

Sorry, this patch is against net-next and you probably tested in Linus'
upstream.

You need to have d160c66cda0ac8614 ("net: Do not return value from
init_dummy_netdev()"), which is in net-next, and has this important
change that is necessary for this patch:

    -int init_dummy_netdev(struct net_device *dev);
    +void init_dummy_netdev(struct net_device *dev);

If you are OK with a v2, I will fix the topics reported in this thread.

Thank you
Breno