netdev - Re: [PATCH net-next 01/10] mlx4: Get rid of the mlx4_interface.get

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Date: Tue, 8 Aug 2023 21:55:17 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Petr Pavlu <petr.pavlu@...e.com>
Cc: tariqt@...dia.com, yishaih@...dia.com, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	jgg@...pe.ca, netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 01/10] mlx4: Get rid of the
 mlx4_interface.get_dev callback

On Fri, Aug 04, 2023 at 05:05:18PM +0200, Petr Pavlu wrote:
> Simplify the mlx4 driver interface by removing mlx4_get_protocol_dev()
> and the associated mlx4_interface.get_dev callbacks. This is done in
> preparation to use an auxiliary bus to model the mlx4 driver structure.
> 
> The change is motivated by the following situation:
> * The mlx4_en interface is being initialized by mlx4_en_add() and
>   mlx4_en_activate().
> * The latter activate function calls mlx4_en_init_netdev() ->
>   register_netdev() to register a new net_device.
> * A netdev event NETDEV_REGISTER is raised for the device.
> * The netdev notififier mlx4_ib_netdev_event() is called and it invokes
>   mlx4_ib_scan_netdevs() -> mlx4_get_protocol_dev() ->
>   mlx4_en_get_netdev() [via mlx4_interface.get_dev].
> 
> This chain creates a problem when mlx4_en gets switched to be an
> auxiliary driver. It contains two device calls which would both need to
> take a respective device lock.
> 
> Avoid this situation by updating mlx4_ib_scan_netdevs() to no longer
> call mlx4_get_protocol_dev() but instead to utilize the information
> passed in net_device.parent and net_device.dev_port. This data is
> sufficient to determine that an updated port is one that the mlx4_ib
> driver should take care of and to keep mlx4_ib_dev.iboe.netdevs up to
> date.
> 
> Following that, update mlx4_ib_get_netdev() to also not call
> mlx4_get_protocol_dev() and instead scan all current netdevs to find
> find a matching one. Note that mlx4_ib_get_netdev() is called early from
> ib_register_device() and cannot use data tracked in
> mlx4_ib_dev.iboe.netdevs which is not at that point yet set.
> 
> Finally, remove function mlx4_get_protocol_dev() and the
> mlx4_interface.get_dev callbacks (only mlx4_en_get_netdev()) as they
> became unused.
> 
> Signed-off-by: Petr Pavlu <petr.pavlu@...e.com>
> Tested-by: Leon Romanovsky <leon@...nel.org>
> ---
>  drivers/infiniband/hw/mlx4/main.c            | 89 ++++++++++----------
>  drivers/net/ethernet/mellanox/mlx4/en_main.c |  8 --
>  drivers/net/ethernet/mellanox/mlx4/intf.c    | 21 -----
>  include/linux/mlx4/driver.h                  |  3 -
>  4 files changed, 43 insertions(+), 78 deletions(-)
> 

Thanks,
Reviewed-by: Leon Romanovsky <leonro@...dia.com>