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From:   Ioana Ciornei <ioana.ciornei@nxp.com>
To:     Tim Gardner <tim.gardner@canonical.com>
CC:     "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        Roy Pledge <Roy.Pledge@nxp.com>, Leo Li <leoyang.li@nxp.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2][net-next] soc: fsl: dpio: Unsigned compared against 0
 in qbman_swp_set_irq_coalescing()
Thread-Topic: [PATCH v2][net-next] soc: fsl: dpio: Unsigned compared against 0
 in qbman_swp_set_irq_coalescing()
Thread-Index: AQHXxOOfZYpKtOnMkEOYlsQsmv2J5qvap5GA
Date:   Tue, 19 Oct 2021 18:39:40 +0000
Message-ID: <20211019183939.bfgpcewtyrutfsky@skbuf>
References: <20211019121925.8910-1-tim.gardner@canonical.com>
In-Reply-To: <20211019121925.8910-1-tim.gardner@canonical.com>
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On Tue, Oct 19, 2021 at 06:19:25AM -0600, Tim Gardner wrote:
> Coverity complains of unsigned compare against 0. There are 2 cases in
> this function:
>=20
> 1821        itp =3D (irq_holdoff * 1000) / p->desc->qman_256_cycles_per_n=
s;
>=20
> CID 121131 (#1 of 1): Unsigned compared against 0 (NO_EFFECT)
> unsigned_compare: This less-than-zero comparison of an unsigned value is =
never true. itp < 0U.
> 1822        if (itp < 0 || itp > 4096) {
> 1823                max_holdoff =3D (p->desc->qman_256_cycles_per_ns * 40=
96) / 1000;
> 1824                pr_err("irq_holdoff must be between 0..%dus\n", max_h=
oldoff);
> 1825                return -EINVAL;
> 1826        }
> 1827
>     	unsigned_compare: This less-than-zero comparison of an unsigned valu=
e is never true. irq_threshold < 0U.
> 1828        if (irq_threshold >=3D p->dqrr.dqrr_size || irq_threshold < 0=
) {
> 1829                pr_err("irq_threshold must be between 0..%d\n",
> 1830                       p->dqrr.dqrr_size - 1);
> 1831                return -EINVAL;
> 1832        }
>=20
> Fix this by removing the comparisons altogether as they are incorrect. Ze=
ro is
> a possible value in either case. Also fix a minor comment typo and update=
 the
> 2 pr_err() calls to use %u formatting as well as be more precise regardin=
g
> the exact error.
>=20
> Fixes: ed1d2143fee5 ("soc: fsl: dpio: add support for irq coalescing per =
software portal")
> Cc: Ioana Ciornei <ioana.ciornei@nxp.com>
> Cc: Roy Pledge <Roy.Pledge@nxp.com>
> Cc: Li Yang <leoyang.li@nxp.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: netdev@vger.kernel.org
> Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>

Thanks,

-Ioana=