linux-kernel - Re: [PATCH net-next] net: create a dummy net

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Message-ID: <20240327161731.6b100cb8@kernel.org>
Date: Wed, 27 Mar 2024 16:17:31 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Breno Leitao <leitao@...ian.org>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 quic_jjohnson@...cinc.com, kvalo@...nel.org, leon@...nel.org,
 dennis.dalessandro@...nelisnetworks.com, Jiri Pirko <jiri@...nulli.us>,
 Simon Horman <horms@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Lorenzo Bianconi <lorenzo@...nel.org>, Coco Li <lixiaoyan@...gle.com>,
 netdev@...r.kernel.org (open list:NETWORKING DRIVERS),
 linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH net-next] net: create a dummy net_device allocator

On Wed, 27 Mar 2024 13:08:04 -0700 Breno Leitao wrote:
> It is impossible to use init_dummy_netdev together with alloc_netdev()
> as the 'setup' argument.
> 
> This is because alloc_netdev() initializes some fields in the net_device
> structure, and later init_dummy_netdev() memzero them all. This causes
> some problems as reported here:
> 
> 	https://lore.kernel.org/all/20240322082336.49f110cc@kernel.org/
> 
> Split the init_dummy_netdev() function in two. Create a new function called
> init_dummy_netdev_core() that does not memzero the net_device structure.
> Then have init_dummy_netdev() memzero-ing and calling
> init_dummy_netdev_core(), keeping the old behaviour.
> 
> init_dummy_netdev_core() is the new function that could be called as an
> argument for alloc_netdev().
> 
> Also, create a helper to allocate and initialize dummy net devices,
> leveraging init_dummy_netdev_core() as the setup argument. This function
> basically simplify the allocation of dummy devices, by allocating and
> initializing it. Freeing the device continue to be done through
> free_netdev()

Ah, but you need to make it part of the series with some caller.
Maybe convert all the ethernet ones?

$ git grep 'struct net_device [^*]*;' -- drivers/net/ethernet/
drivers/net/ethernet/cavium/thunder/thunder_bgx.c:      struct net_device       netdev;
drivers/net/ethernet/marvell/prestera/prestera_rxtx.c:  struct net_device napi_dev;
drivers/net/ethernet/microchip/vcap/vcap_api_debugfs_kunit.c:static struct net_device test_netdev = {};
drivers/net/ethernet/microchip/vcap/vcap_api_kunit.c:static struct net_device test_netdev = {};
-- 
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