linux-kernel - Re: [PATCH net-next v7 4/8] net: stmmac: Introduce stmmac_fpe

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Message-ID: <20241031173946.53ydl7v7gihtdkx5@skbuf>
Date: Thu, 31 Oct 2024 19:39:46 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: Furong Xu <0x1207@...il.com>
Cc: netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Andrew Lunn <andrew@...n.ch>, Simon Horman <horms@...nel.org>,
	andrew+netdev@...n.ch,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Jose Abreu <joabreu@...opsys.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>, xfr@...look.com
Subject: Re: [PATCH net-next v7 4/8] net: stmmac: Introduce
 stmmac_fpe_supported()

On Thu, Oct 31, 2024 at 08:37:58PM +0800, Furong Xu wrote:
> Call stmmac_fpe_supported() to check both HW capability and
> driver capability to keep FPE as an optional implementation
> for current and new MAC cores.
> 
> Signed-off-by: Furong Xu <0x1207@...il.com>
> ---

Doesn't this commit actually fix a bug which patch 3/8 introduced?
If priv->fpe_cfg.reg is NULL, we will dereference that after just
patch 3/8 has been applied. During e.g. a git bisect landing in between,
that crash might be seen by users.

Thus, please reorder these 2 patches to prevent the bug from existing in
the first place, and say in the commit message that the reason for the
introduction of stmmac_fpe_supported() - initially simply implemented as
a single "priv->dma_cap.fpesel" check - is to prevent unexpected
behavior on unsupported FPE MACs during further refactoring.

Then, the patch "net: stmmac: Refactor FPE functions to generic version"
should be the one which also reimplements stmmac_fpe_supported() to
check for the presence of the newly added primitives.