Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Message-ID: <19ea2a8ff04c24708a6504924f7a91c1045308d0.camel@linux.ibm.com>
Subject: Re: [PATCH v4 1/4] PCI: Clean up pci_scan_slot()
From:   Niklas Schnelle <schnelle@linux.ibm.com>
To:     Bjorn Helgaas <bhelgaas@google.com>,
        Jan Kiszka <jan.kiszka@siemens.com>,
        Matthew Rosato <mjrosato@linux.ibm.com>,
        Pierre Morel <pmorel@linux.ibm.com>
Cc:     linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        linux-s390@vger.kernel.org, linux-pci@vger.kernel.org
Date:   Fri, 22 Apr 2022 15:35:07 +0200
In-Reply-To: <20220422132858.1213022-2-schnelle@linux.ibm.com>
References: <20220422132858.1213022-1-schnelle@linux.ibm.com>
         <20220422132858.1213022-2-schnelle@linux.ibm.com>
Content-Type: multipart/signed; micalg="pgp-sha256";
        protocol="application/pgp-signature"; boundary="=-+5TQTceV7kwkEleY1vza"
Mime-Version: 1.0
Precedence: bulk


--=-+5TQTceV7kwkEleY1vza
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Fri, 2022-04-22 at 15:28 +0200, Niklas Schnelle wrote:
> While determining the next PCI function is factored out of
> pci_scan_slot() into next_fn() the former still handles the first
> function as a special case. This duplicates the code from the scan loop.
>=20
> Furthermore the non ARI branch of next_fn() is generally hard to
> understand and especially the check for multifunction devices is hidden
> in the handling of NULL devices for non-contiguous multifunction. It
> also signals that no further functions need to be scanned by returning
> 0 via wraparound and this is a valid function number.
>=20
> Improve upon this by transforming the conditions in next_fn() to be
> easier to understand.
>=20
> By changing next_fn() to return -ENODEV instead of 0 when there is no
> next function we can then handle the initial function inside the loop
> and deduplicate the shared handling. This also makes it more explicit
> that only function 0 must exist.
>=20
> No functional change is intended.
>=20
> Cc: Jan Kiszka <jan.kiszka@siemens.com>
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> ---
>  drivers/pci/probe.c | 39 ++++++++++++++++++++-------------------
>  1 file changed, 20 insertions(+), 19 deletions(-)
>=20
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 17a969942d37..2000e9858f12 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2579,8 +2579,7 @@ struct pci_dev *pci_scan_single_device(struct pci_b=
us *bus, int devfn)
>  }
>  EXPORT_SYMBOL(pci_scan_single_device);
> =20
> -static unsigned int next_fn(struct pci_bus *bus, struct pci_dev *dev,
> -			    unsigned int fn)
> +static int next_fn(struct pci_bus *bus, struct pci_dev *dev, int fn)
>  {
>  	int pos;
>  	u16 cap =3D 0;
> @@ -2588,24 +2587,27 @@ static unsigned int next_fn(struct pci_bus *bus, =
struct pci_dev *dev,
> =20
>  	if (pci_ari_enabled(bus)) {
>  		if (!dev)
> -			return 0;
> +			return -ENODEV;
> +
>=20

Sorry the whitespace damage was of course not intended, fixed locally.


--=-+5TQTceV7kwkEleY1vza
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: This is a digitally signed message part
Content-Transfer-Encoding: 7bit

-----BEGIN PGP SIGNATURE-----

iHUEABYIAB0WIQSiikNOrnCUNbxSj4j7H22hwInkVgUCYmKvCwAKCRD7H22hwInk
VuHsAP4kfYFxmlqA+DTbxpABv2slW9y+gv3ZVfhol3ARhACQTAEA7eHZ1cfNp120
EPzOHKOZgvgB4WoqBZ3lks5BKp7bhQg=
=esXt
-----END PGP SIGNATURE-----

--=-+5TQTceV7kwkEleY1vza--