linux-kernel - Re: [PATCH V4 1/1] Intel Sky Lake-E host root ports check.

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Message-ID: <20220330191017.GA1700536@bhelgaas>
Date:   Wed, 30 Mar 2022 14:10:17 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Shlomo Pongratz <shlomopongratz@...il.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        andrew.maier@...eticom.com, logang@...tatee.com,
        bhelgaas@...gle.com, Shlomo Pongratz <shlomop@...ops.com>
Subject: Re: [PATCH V4 1/1] Intel Sky Lake-E host root ports check.

On Wed, Mar 30, 2022 at 12:37:20PM -0300, Jason Gunthorpe wrote:
> On Wed, Mar 30, 2022 at 05:08:23PM +0300, Shlomo Pongratz wrote:
> > @@ -350,7 +353,10 @@ static struct pci_dev *pci_host_bridge_dev(struct pci_host_bridge *host)
> >  
> >  	if (!root)
> >  		return NULL;
> > -	if (root->devfn != PCI_DEVFN(0, 0))
> > +
> > +	/* Is it a host bridge or a root port? */
> 
> This is a better comment:
> 
> /* host bridges must have a 0 devfn, but some of the entries in the
>   whilelist are root ports that can have any devfn */

Is this something in the spec or is it just common practice?  The PCIe
spec says very little about "host bridges" and I don't remember
anything about them having to be devfn 0 or even that they have to be
materialized as PCI devices.

> > +	if (root->devfn != PCI_DEVFN(0, 0) &&
> > +		pci_pcie_type(root) != PCI_EXP_TYPE_ROOT_PORT)
> >  		return NULL;
> 
> Indentation is wrong
> 
> Jason