linux-kernel - Re: [PATCH] ath10k: allocate dummy net

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Message-ID: <20240321151744.246ce2d0@kernel.org>
Date: Thu, 21 Mar 2024 15:17:44 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Jeff Johnson <quic_jjohnson@...cinc.com>
Cc: Breno Leitao <leitao@...ian.org>, Kalle Valo <kvalo@...nel.org>, Jeff
 Johnson <jjohnson@...nel.org>, <keescook@...omium.org>, "open
 list:NETWORKING DRIVERS (WIRELESS)" <linux-wireless@...r.kernel.org>, "open
 list:QUALCOMM ATHEROS ATH10K WIRELESS DRIVER" <ath10k@...ts.infradead.org>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ath10k: allocate dummy net_device dynamically

On Thu, 21 Mar 2024 15:02:39 -0700 Jeff Johnson wrote:
> >> As suggested there we should just use kmalloc/kfree to match the existing logic.  
> > 
> > Please no. There is no magic here. alloc + free must match whether
> > you're using magic object alloc wrapper (alloc_netdev()) or straight
> > up kzalloc().  
> 
> Based upon the ath11k patch there must be something going on with
> alloc_netdev()/free_netdev() that doesn't occur when these aren't used.

Looks like init_dummy_netdev wipes the netdev structure clean, so I
don't think we can use it directly as the setup function, Breno :(
Maybe we should add a new helper to "alloc dummy netdev" which can
call alloc_netdev() with right arguments and do necessary init?

> So I'm just suggesting that instead we use kmalloc() and kfree(), which are
> matching functions, and which, like the existing code, are not subject to
> whatever is happening in alloc_netdev()/free_netdev().
> 
> I don't understand your objection.

Using subsystem APIs to allocate its objects is preferable to ad hoc
kmalloc().

We're working upstream, basic alloc/free of an object should work.
Took me 5 min to realize what the problem is.