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Date: Tue, 15 Nov 2022 18:43:05 +0100
From: Andrew Lunn <andrew@lunn.ch>
To: Shenwei Wang <shenwei.wang@nxp.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	Ilias Apalodimas <ilias.apalodimas@linaro.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	John Fastabend <john.fastabend@gmail.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"imx@lists.linux.dev" <imx@lists.linux.dev>
Subject: Re: [EXT] Re: [PATCH v4 1/2] net: page_pool: export page_pool_stats
 definition
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References: <20221115155744.193789-1-shenwei.wang@nxp.com>
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> > I agree the API is broken, but i think there is a better fix.
> > 
> > There should be a stub of page_pool_get_stats() for when
> > CONFIG_PAGE_POOL_STATS is disabled.
> > 
> > Nothing actually dereferences struct page_pool_stats when you have this stub.
> > So it might be enough to simply have
> > 
> > struct page_pool_stats{
> > };
> > 
> 
> As the structure is open when the CONFIG_PAGE_POOL_STATS is enabled, you can not
> prevent a user to access its members. The empty stub will still have problems in this
> kind of situations.

The users, i.e. the driver, has no need to access its members. The
members can change, new ones can be added, and it will not cause a
problem, given the way this API is defined. Ideally, page_pool_stats
would of been an opaque cookie, but that is not how it was
implemented :-(

	    Andrew