linux-kernel - Re: [PATCH] ARM: PCI: Use PCI_CLASS

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Date:	Mon, 04 Aug 2014 11:31:08 +0200
From:	Rostislav Lisovy <lisovy@...il.com>
To:	Sasha Levin <sashal@...nel.org>
Cc:	Russell King <linux@....linux.org.uk>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yijing Wang <wangyijing@...wei.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Nicholas Krause <xerofoify@...il.com>
Subject: Re: [PATCH] ARM: PCI: Use PCI_CLASS_* defines for PCI class

On Sun, 2014-08-03 at 09:16 -0400, Sasha Levin wrote:
> > -     /* FIXME: add defines for class 0x68000 and 0x80103 */
> >       if ((dev->class >> 8) == PCI_CLASS_BRIDGE_HOST ||
> > -         dev->class == 0x68000 ||
> > -         dev->class == 0x80103) {
> > +         dev->class == (PCI_CLASS_BRIDGE_OTHER << 8) ||
> > +         dev->class == ((PCI_CLASS_SYSTEM_DMA << 8) | 0x03)) {
> >               for (i = 0; i < PCI_NUM_RESOURCES; i++) {
> >                       dev->resource[i].start = 0;
> >                       dev->resource[i].end   = 0;
> > 
> 
> Care to explain how your new code is equivalent to the old one?

The header file include/linux/pci_ids.h defines
#define PCI_CLASS_BRIDGE_OTHER          0x0680
#define PCI_CLASS_SYSTEM_DMA            0x0801

((struct pci_dev*)dev)->class
corresponds to the 3 bytes Class code in the PCI Configuration space
header -- 1B Base class, 1B Sub-class, 1B Reg-level interface.

In that case
(PCI_CLASS_BRIDGE_OTHER << 8)
is equivalent to 0x68000 (imagine the leading zero)
and
((PCI_CLASS_SYSTEM_DMA << 8) | 0x03))
is equivalent to 0x80103.

Best regards;
Rostislav


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