Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37;
Date:   Mon, 30 Oct 2023 16:30:48 +0100
From:   Thierry Reding <thierry.reding@gmail.com>
To:     Baolu Lu <baolu.lu@linux.intel.com>
Cc:     Dario Binacchi <dario.binacchi@amarulasolutions.com>,
        linux-kernel@vger.kernel.org, Joerg Roedel <joro@8bytes.org>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Krishna Reddy <vdumpa@nvidia.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Will Deacon <will@kernel.org>, iommu@lists.linux.dev,
        linux-tegra@vger.kernel.org
Subject: Re: [PATCH] iommu/tegra-smmu: fix error checking for
 debugfs_create_dir()
Message-ID: <ZT_MKDVkqMECiv4I@orome.fritz.box>
References: <20231025110140.2034650-1-dario.binacchi@amarulasolutions.com>
 <1acd75d0-67a7-4a17-99c7-707cca305f37@linux.intel.com>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha256;
        protocol="application/pgp-signature"; boundary="tiC6UW8JeMZZZOlp"
Content-Disposition: inline
In-Reply-To: <1acd75d0-67a7-4a17-99c7-707cca305f37@linux.intel.com>
User-Agent: Mutt/2.2.12 (2023-09-09)
Precedence: bulk


--tiC6UW8JeMZZZOlp
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Wed, Oct 25, 2023 at 07:25:50PM +0800, Baolu Lu wrote:
> On 2023/10/25 19:01, Dario Binacchi wrote:
> > The return value of debugfs_create_dir() should be checked using the
> > IS_ERR() function.
> >=20
> > Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
> > ---
> >=20
> >   drivers/iommu/tegra-smmu.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >=20
> > diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
> > index e445f80d0226..cd1d80c4c673 100644
> > --- a/drivers/iommu/tegra-smmu.c
> > +++ b/drivers/iommu/tegra-smmu.c
> > @@ -1056,7 +1056,7 @@ DEFINE_SHOW_ATTRIBUTE(tegra_smmu_clients);
> >   static void tegra_smmu_debugfs_init(struct tegra_smmu *smmu)
> >   {
> >   	smmu->debugfs =3D debugfs_create_dir("smmu", NULL);
> > -	if (!smmu->debugfs)
> > +	if (IS_ERR(smmu->debugfs))
> >   		return;
>=20
> This check can be removed, as debugfs_create_file() can handle the case
> where @parent is an error pointer.

A patch for this has been in linux-next for a few weeks, see:

commit f7da9c081517daba70f9f9342e09d7a6322ba323
Author: Jinjie Ruan <ruanjinjie@huawei.com>
Date:   Fri Sep 1 15:30:56 2023 +0800

    iommu/tegra-smmu: Drop unnecessary error check for for debugfs_create_d=
ir()
   =20
    The debugfs_create_dir() function returns error pointers.
    It never returns NULL.
   =20
    As Baolu suggested, this patch removes the error checking for
    debugfs_create_dir in tegra-smmu.c. This is because the DebugFS kernel =
API
    is developed in a way that the caller can safely ignore the errors that
    occur during the creation of DebugFS nodes. The debugfs APIs have
    a IS_ERR() judge in start_creating() which can handle it gracefully. So
    these checks are unnecessary.
   =20
    Fixes: d1313e7896e9 ("iommu/tegra-smmu: Add debugfs support")
    Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
    Suggested-by: Baolu Lu <baolu.lu@linux.intel.com>
    Acked-by: Thierry Reding <treding@nvidia.com>
    Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
    Link: https://lore.kernel.org/r/20230901073056.1364755-1-ruanjinjie@hua=
wei.com
    Signed-off-by: Joerg Roedel <jroedel@suse.de>

Thierry

--tiC6UW8JeMZZZOlp
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=+7dL
-----END PGP SIGNATURE-----

--tiC6UW8JeMZZZOlp--