netdev - Re: [PATCH RFC net-next 01/15] net: phylink: add PCS negotiation mode

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Date: Tue, 13 Jun 2023 17:55:11 +0200
From: Simon Horman <simon.horman@...igine.com>
To: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
Cc: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
	Alexander Couzens <lynxis@...0.eu>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Cc@....codeaurora.org: 
	Claudiu Beznea <claudiu.beznea@...rochip.com>,
	Daniel Golle <daniel@...rotopia.org>,
	Daniel Machon <daniel.machon@...rochip.com>,
	"David S. Miller" <davem@...emloft.net>,
	DENG Qingfang <dqfext@...il.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Horatiu Vultur <horatiu.vultur@...rochip.com>,
	Ioana Ciornei <ioana.ciornei@....com>,
	Jakub Kicinski <kuba@...nel.org>,
	Jose Abreu <Jose.Abreu@...opsys.com>,
	Landen Chao <Landen.Chao@...iatek.com>,
	Lars Povlsen <lars.povlsen@...rochip.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org,
	Madalin Bucur <madalin.bucur@....com>,
	Marcin Wojtas <mw@...ihalf.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Michal Simek <michal.simek@....com>, netdev@...r.kernel.org,
	Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Radhey Shyam Pandey <radhey.shyam.pandey@...inx.com>,
	Sean Anderson <sean.anderson@...o.com>,
	Sean Wang <sean.wang@...iatek.com>,
	Steen Hegelund <Steen.Hegelund@...rochip.com>,
	Taras Chornyi <taras.chornyi@...ision.eu>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	UNGLinuxDriver@...rochip.com, Vladimir Oltean <olteanv@...il.com>
Subject: Re: [PATCH RFC net-next 01/15] net: phylink: add PCS negotiation mode

On Tue, Jun 13, 2023 at 03:37:32PM +0100, Russell King (Oracle) wrote:

...

> @@ -1149,12 +1159,20 @@ static int phylink_change_inband_advert(struct phylink *pl)

Hi Russell,

A bit further above in this function is the following condition:

        if (!pl->pcs && pl->config->legacy_pre_march2020) {
		...
		return 0;
	}

So it is anticipated that pl->pcs may be NULL,
but the function will continue unless
pl->config->legacy_pre_march2020 is true.


>  		    __ETHTOOL_LINK_MODE_MASK_NBITS, pl->link_config.advertising,
>  		    pl->link_config.pause);
>  
> +	/* Recompute the PCS neg mode */
> +	pl->pcs_neg_mode = phylink_pcs_neg_mode(pl->cur_link_an_mode,
> +					pl->link_config.interface,
> +					pl->link_config.advertising);

	nit: this indentation is incorrect.

> +
> +	neg_mode = pl->cur_link_an_mode;
> +	if (pl->pcs->neg_mode)

But Smatch flags that here pl->pcs is dereferenced unconditionally.

> +		neg_mode = pl->pcs_neg_mode;
> +
>  	/* Modern PCS-based method; update the advert at the PCS, and
>  	 * restart negotiation if the pcs_config() helper indicates that
>  	 * the programmed advertisement has changed.
>  	 */
> -	ret = phylink_pcs_config(pl->pcs, pl->cur_link_an_mode,
> -				 &pl->link_config,
> +	ret = phylink_pcs_config(pl->pcs, neg_mode, &pl->link_config,
>  				 !!(pl->link_config.pause & MLO_PAUSE_AN));
>  	if (ret < 0)
>  		return ret;