linux-kernel - Re: [PATCH net-next 07/15] net: dsa: mt7530: do not run mt7530_setup

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Message-ID: <9b729dab-aebc-4c0c-a5e1-164845cd0948@suswa.mountain>
Date:   Fri, 8 Dec 2023 07:23:38 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Arınç ÜNAL <arinc.unal@...nc9.com>,
        Simon Horman <horms@...nel.org>,
        Daniel Golle <daniel@...rotopia.org>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Frank Wunderlich <frank-w@...lic-files.de>,
        Bartel Eerdekens <bartel.eerdekens@...stell8.be>,
        mithat.guner@...ont.com, erkin.bozoglu@...ont.com
Subject: Re: [PATCH net-next 07/15] net: dsa: mt7530: do not run
 mt7530_setup_port5() if port 5 is disabled

On Thu, Dec 07, 2023 at 08:40:15PM +0200, Vladimir Oltean wrote:
> 
> We could be more pragmatic about this whole sparse false positive warning,
> and just move the "if" block which calls mt7530_setup_port5() right
> after the priv->p5_intf_sel assignments, instead of waiting to "break;"
> from the for_each_child_of_node() loop.
> 
> for_each_child_of_node(dn, mac_np) {
> 	if (!of_device_is_compatible(mac_np,
> 				     "mediatek,eth-mac"))
> 		continue;
> 
> 	ret = of_property_read_u32(mac_np, "reg", &id);
> 	if (ret < 0 || id != 1)
> 		continue;
> 
> 	phy_node = of_parse_phandle(mac_np, "phy-handle", 0);
> 	if (!phy_node)
> 		continue;
> 
> 	if (phy_node->parent == priv->dev->of_node->parent) {
> 		ret = of_get_phy_mode(mac_np, &interface);
> 		if (ret && ret != -ENODEV) {
> 			of_node_put(mac_np);
> 			of_node_put(phy_node);
> 			return ret;
> 		}
> 		id = of_mdio_parse_addr(ds->dev, phy_node);
> 		if (id == 0)
> 			priv->p5_intf_sel = P5_INTF_SEL_PHY_P0;
> 		if (id == 4)
> 			priv->p5_intf_sel = P5_INTF_SEL_PHY_P4;
> 
> 		if (priv->p5_intf_sel == P5_INTF_SEL_PHY_P0 || <---- here
> 		    priv->p5_intf_sel == P5_INTF_SEL_PHY_P4)
> 			mt7530_setup_port5(ds, interface);

This doesn't solve the problem that Smatch doesn't know what the
original value of priv->p5_intf_sel.  And also I don't like this code
because now we call mt7530_setup_port5() on every iteration after
we find the first P5_INTF_SEL_PHY_P0.

> 	}
> 	of_node_put(mac_np);
> 	of_node_put(phy_node);
> 	break;
> }

Let's not worry too much about false positives.  We can just ignore
them.  There is always a trade off between false positives and false
negatives.  With GCC we try to get a clean run with no warnings, but
with Smatch I'm targetting the false positive ratio at "this is worth
reviewing one time."

regards,
dan carpenter