netdev - re: can: flexcan: add mcf5441x support

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Date:   Tue, 3 Aug 2021 16:23:26 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Angelo Dureghello <angelo@...nel-space.org>
Cc:     Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-can@...r.kernel.org,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: re: can: flexcan: add mcf5441x support

Hi,

Static analysis of linux-next with Coverity has detected a potential
issue with the following commit:

commit d9cead75b1c66b4660b4f87ff339234042d7c6a5
Author: Angelo Dureghello <angelo@...nel-space.org>
Date:   Fri Jul 2 11:48:41 2021 +0200

    can: flexcan: add mcf5441x support

The analysis is as follows:

650 static int flexcan_clks_enable(const struct flexcan_priv *priv)
651 {

   1. var_decl: Declaring variable err without initializer.

652        int err;
653

   2. Condition priv->clk_ipg, taking false branch.

654        if (priv->clk_ipg) {
655                err = clk_prepare_enable(priv->clk_ipg);
656                if (err)
657                        return err;
658        }
659

   3. Condition priv->clk_per, taking false branch.

660        if (priv->clk_per) {
661                err = clk_prepare_enable(priv->clk_per);
662                if (err)
663                        clk_disable_unprepare(priv->clk_ipg);
664        }
665

   Uninitialized scalar variable (UNINIT)
   4. uninit_use: Using uninitialized value err.

666        return err;
667 }

I'm not sure if it's possible for priv->clk_ipg and priv_clk_per to both
be null, so I'm not sure if err can end up being not set. However, it
does seem that either err should be zero or some err value, but I was
unsure how err should be initialized in this corner case. As it stands,
err probably needs to be set just to be safe.

Colin