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From:   "Tian, Kevin" <kevin.tian@intel.com>
To:     Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>
CC:     "x86@kernel.org" <x86@kernel.org>, Joerg Roedel <joro@8bytes.org>,
        "Will Deacon" <will@kernel.org>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        "Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
        Marc Zyngier <maz@kernel.org>,
        "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
        Jason Gunthorpe <jgg@mellanox.com>,
        "Jiang, Dave" <dave.jiang@intel.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        "Williams, Dan J" <dan.j.williams@intel.com>,
        Logan Gunthorpe <logang@deltatee.com>,
        "Raj, Ashok" <ashok.raj@intel.com>, Jon Mason <jdmason@kudzu.us>,
        Allen Hubbe <allenbh@gmail.com>
Subject: RE: [patch V2 07/33] genirq/msi: Provide
 msi_create/free_device_irq_domain()
Thread-Topic: [patch V2 07/33] genirq/msi: Provide
 msi_create/free_device_irq_domain()
Thread-Index: AQHY/bblStmeh1OioEClNZ/eww2WyK5MCblggABa9gCAAN5AcA==
Date:   Thu, 24 Nov 2022 01:07:07 +0000
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> From: Thomas Gleixner <tglx@linutronix.de>
> Sent: Wednesday, November 23, 2022 7:38 PM
>=20
> >> + *
> >> + * Return: True on success, false otherwise
> >
> > Can you elaborate why boolean type is selected instead of returning the
> > actual error codes? the outmost callers are all new functions:
> >
> > 	pci_setup_msi[x]_device_domain()
> > 	pci_create_ims_domain()
> >
> > I didn't find out any legacy convention forcing this way...
>=20
> What's the value of error codes? 99% of all callsites do:
>=20
>        ret =3D foo();
>        if (ret)
>           goto fail;
>=20
> Nothing evaluates the error codes, unless there is real useful
> information like EAGAIN or ENOSPC which can tell the caller to retry
> eventually or with different parameters. But for the above, the error
> code is just useless.
>=20

I looked at it from the outmost invocation:

@@ -436,6 +436,9 @@ int __pci_enable_msi_range(struct pci_de
 	if (rc)
 		return rc;
=20
+	if (!pci_setup_msi_device_domain(dev))
+		return -ENODEV;
+

the current style kind of converts meaningful -EINVAL/-ENOMEM/etc.
into -ENODEV.