Received-SPF: pass (google.com: domain of linux-kernel+bounces-16291-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Date: Wed, 3 Jan 2024 22:43:40 -0800
From: Dan Williams <dan.j.williams@intel.com>
To: Lukas Wunner <lukas@wunner.de>, Ira Weiny <ira.weiny@intel.com>
CC: Dan Williams <dan.j.williams@intel.com>, Jonathan Cameron
	<jonathan.cameron@huawei.com>, Smita Koralahalli
	<Smita.KoralahalliChannabasappa@amd.com>, Shiju Jose <shiju.jose@huawei.com>,
	Yazen Ghannam <yazen.ghannam@amd.com>, Davidlohr Bueso <dave@stgolabs.net>,
	Dave Jiang <dave.jiang@intel.com>, Alison Schofield
	<alison.schofield@intel.com>, Vishal Verma <vishal.l.verma@intel.com>, "Ard
 Biesheuvel" <ardb@kernel.org>, <linux-efi@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <linux-cxl@vger.kernel.org>, Bjorn Helgaas
	<bhelgaas@google.com>
Subject: Re: [PATCH v5 8/9] PCI: Define scoped based management functions
Message-ID: <6596539c9729e_8dc6829476@dwillia2-xfh.jf.intel.com.notmuch>
References: <20231220-cxl-cper-v5-0-1bb8a4ca2c7a@intel.com>
 <20231220-cxl-cper-v5-8-1bb8a4ca2c7a@intel.com>
 <20240104060528.GA10504@wunner.de>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <20240104060528.GA10504@wunner.de>
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?eZ4Y7cR7UoCrgt7btqeg2OIiaIPICWBpGRHhnKJ482ckgkUWUKHFhnOecU2m?=
 =?us-ascii?Q?6bo+bsJwrNzrvcVnB7Zhy0/1V0/cZr22BZZvciL+C8dyB6nIa6fcxwPZHd+y?=
 =?us-ascii?Q?vC4t3HTivWp3DS7/V9jgq3GHYJtf7Biv8tXR1ZOgXb7zsLh0b3oRKdKh/f0u?=
 =?us-ascii?Q?LsZTzUqy5/sCY+Bez3OG3/FVsZTEye/4hZVLPSn0espXFKBhTFF0+a1gD17O?=
 =?us-ascii?Q?LeP4r8rQMU2VRWphTTqIJgTJZxPEKQMECxi1f3unjLkjplMOhsKo+9T59CZK?=
 =?us-ascii?Q?ktVBmQ0uDwI3vNpsGY5klWaHiSXETSdRri4L5bxfTaHQHMcRjLzTChX9u1em?=
 =?us-ascii?Q?qyZmPPDHSMaGnuCYmBluMk9pdDGkC7lk1Y1liVS1KsOYZcTL2EnFHtwZSZAE?=
 =?us-ascii?Q?zDtCwnB+c4opFDLGl+eZvxDm0LoPYXk5AvDoqe9nnHh2XRsQPoymuEs7rekO?=
 =?us-ascii?Q?y4rLVwiE2zEJocDxUR8jbxD56Sbgi9xyxZzUeHcCIdyu9gwRc5OSlAeHc9N7?=
 =?us-ascii?Q?v1po58hWVUDJgHW4/I3XQPHggP54q0rziewZFmYjHspZYEzqL2pKSioBKhcN?=
 =?us-ascii?Q?Xt7KlxfcwRaB7nowVnPgF3o3RmwI2mmry95EPc6s5JX6LA09OJB322CWdUpS?=
 =?us-ascii?Q?b4SUXhohY+xXBWmscQ2dyIbtXkeq6a90SBxUck5ffRkOVjevccEK/UvW20wl?=
 =?us-ascii?Q?t2LXaBCWfqPfqb8dFDY3GI9nfA74fdx7gEaDOBiArO6tuCjY3RvvWkNR2Ja+?=
 =?us-ascii?Q?pxLli/xviVz+2mzjPea+UhQ9k3P1FA9HqDhG2WIVEXCBB7F5+69W6424EGj9?=
 =?us-ascii?Q?qjVxtpgH4BHLxwWXNcTn8Kgyk4O3FonnKhFrcd+UdHD1sNBP8E14N2qDUqoq?=
 =?us-ascii?Q?Ztorl2jrVtLOJ76b9V/O5PMAzlN/lVTdC/2rM6/rxMx8oTAPIW+pkHUTSigq?=
 =?us-ascii?Q?vfFjJ8p+w/OPvgTIrcLsriLVqxQkAN4+p4t6UdYOvOs/T3M8ByBIZbHWQtyS?=
 =?us-ascii?Q?6z4v1rQdrrjfTWNyM+MJmcef+xAwtylNKnEL+xqYZwTimcQjvCWYl8o3UTZV?=
 =?us-ascii?Q?Vh2GJykUZuRnwjcNND2mN4vB95mBPaMmwtkjG/Gbz+VuimphBhVcpABGZi3H?=
 =?us-ascii?Q?fHLbptXl1ZfhqVqdf5ahGVo8nw0dLxhQRyWI28oyFVM1Tr7cxM/WehfhAll9?=
 =?us-ascii?Q?CO9aBzDXaoh8Zu12BijoE3t01XlemO3l222hJq/zRnPamiwdT+kWukZQzdLX?=
 =?us-ascii?Q?i0kyHq5A/RGHzWt+Q7ffy7NcBzBFOkz25/349xCC/LSHxJ0q1+pwIsoZ8z4x?=
 =?us-ascii?Q?ukNQemBepZNZ8qXIJtsEC6Lm31ZVRmZ+jMmw3tew5eea+hvNFIW+RXYozpyG?=
 =?us-ascii?Q?33Zpe7ISz97bsGoh+jhBE4K2CUsVKqI8MuhB+ddgeh7jMcA1VhOwAnfuYjl8?=
 =?us-ascii?Q?/Fx6qrdEnJBuNhlapPuTyo4YLJcDaYGp9foGVJXRLxZW+F19HpV/KUeD9LhM?=
 =?us-ascii?Q?FHUj0FT4pb4DM/KaGgGeJM9KoStMbTXZ5MgpYnpq4mOwzDINmm0syQhW/Cmx?=
 =?us-ascii?Q?cBltVghqU/6E0GNRdkEw9JSv6xn/Omy8q49iFjASYXBnOa3uF3rHYUyRsTR5?=
 =?us-ascii?Q?rQ=3D=3D?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 8fd4dfe6-8891-453b-efc3-08dc0cf07edb
X-MS-Exchange-CrossTenant-AuthSource: PH8PR11MB8107.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Jan 2024 06:43:44.1048
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: Uo/8V75jlevDr4P30cteT+Z2PNCO9biO5dwaQoJRzmVmS+b39+IEvtiFSAeokxlX4HOLFiNkDZCwu8cDUZzhk6tDopBOEu7jVBhnFAGT0/M=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR11MB5352
X-OriginatorOrg: intel.com

Lukas Wunner wrote:
> On Wed, Dec 20, 2023 at 04:17:35PM -0800, Ira Weiny wrote:
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -1170,6 +1170,7 @@ int pci_get_interrupt_pin(struct pci_dev *dev, struct pci_dev **bridge);
> >  u8 pci_common_swizzle(struct pci_dev *dev, u8 *pinp);
> >  struct pci_dev *pci_dev_get(struct pci_dev *dev);
> >  void pci_dev_put(struct pci_dev *dev);
> > +DEFINE_FREE(pci_dev_put, struct pci_dev *, if (_T) pci_dev_put(_T))
> 
> pci_dev_put() already performs a NULL pointer check internally.
> Why duplicate it here?

Greg asked the same for the introduction of __free(kvfree), and Peter
clarified:

http://lore.kernel.org/r/20230814161731.GN776869@hirez.programming.kicks-ass.net

Essentially, that check is more for build-time than runtime because when
the macro is expanded the compiler can notice scenarios where @pdev is
set to NULL (likely by no_free_ptr()) and skip the call to pci_dev_put()
altogether. pci_dev_put() also happens to be out-of-line, so saving a
call when @pdev is NULL a small win in that respect as well.