linux-kernel - Re: [PATCH v2] PCI: Add defines for normal and subtractive PCI bridges

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Message-ID: <20211220175130.bogovgjofevwfohn@pali>
Date:   Mon, 20 Dec 2021 18:51:30 +0100
From:   Pali Rohár <pali@...nel.org>
To:     Lukas Wunner <lukas@...ner.de>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczy??ski <kw@...ux.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI: Add defines for normal and subtractive PCI
 bridges

On Monday 20 December 2021 17:21:50 Lukas Wunner wrote:
> On Mon, Dec 20, 2021 at 03:51:40PM +0100, Pali Rohár wrote:
> > --- a/drivers/pci/pcie/portdrv_pci.c
> > +++ b/drivers/pci/pcie/portdrv_pci.c
> > @@ -178,9 +178,9 @@ static pci_ers_result_t pcie_portdrv_mmio_enabled(struct pci_dev *dev)
> >   */
> >  static const struct pci_device_id port_pci_ids[] = {
> >  	/* handle any PCI-Express port */
> > -	{ PCI_DEVICE_CLASS(((PCI_CLASS_BRIDGE_PCI << 8) | 0x00), ~0) },
> > +	{ PCI_DEVICE_CLASS(PCI_CLASS_BRIDGE_PCI_NORMAL, ~0) },
> >  	/* subtractive decode PCI-to-PCI bridge, class type is 060401h */
> > -	{ PCI_DEVICE_CLASS(((PCI_CLASS_BRIDGE_PCI << 8) | 0x01), ~0) },
> > +	{ PCI_DEVICE_CLASS(PCI_CLASS_BRIDGE_PCI_SUBTRACTIVE, ~0) },
> 
> Any harm in simply matching for 0x060400 with mask 0xffff00?

Currently are defined only class ids 0x060400 and 0x060401. I'm not sure
if PCI-SIG cannot define in future other class ids (e.g. 0x060402,
0x060403, ...) for purposes not compatible with this driver...

Anyway, proposed suggestion changes behavior in code and my patch just
add macros without changing code. So it should not be done as part of
this my patch.