linux-kernel - Re: [PATCH 2/16 v6] PCI: define PCI resource names in an 'enum'

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Date:	Wed, 22 Oct 2008 08:24:19 -0600
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Yu Zhao <yu.zhao@...el.com>
Cc:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"achiang@...com" <achiang@...com>,
	"grundler@...isc-linux.org" <grundler@...isc-linux.org>,
	"greg@...ah.com" <greg@...ah.com>, "mingo@...e.hu" <mingo@...e.hu>,
	"jbarnes@...tuousgeek.org" <jbarnes@...tuousgeek.org>,
	"matthew@....cx" <matthew@....cx>,
	"randy.dunlap@...cle.com" <randy.dunlap@...cle.com>,
	"rdreier@...co.com" <rdreier@...co.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"virtualization@...ts.linux-foundation.org" 
	<virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH 2/16 v6] PCI: define PCI resource names in an 'enum'

On Wednesday 22 October 2008 02:40:41 am Yu Zhao wrote:
> This patch moves all definitions of the PCI resource names to an 'enum',
> and also replaces some hard-coded resource variables with symbol
> names. This change eases introduction of device specific resources.

Thanks for removing a bunch of magic numbers from the code.

>  static void
>  pci_restore_bars(struct pci_dev *dev)
>  {
> -	int i, numres;
> -
> -	switch (dev->hdr_type) {
> -	case PCI_HEADER_TYPE_NORMAL:
> -		numres = 6;
> -		break;
> -	case PCI_HEADER_TYPE_BRIDGE:
> -		numres = 2;
> -		break;
> -	case PCI_HEADER_TYPE_CARDBUS:
> -		numres = 1;
> -		break;
> -	default:
> -		/* Should never get here, but just in case... */
> -		return;
> -	}
> +	int i;
>  
> -	for (i = 0; i < numres; i++)
> +	for (i = 0; i < PCI_BRIDGE_RESOURCES; i++)
>  		pci_update_resource(dev, i);
>  }

The behavior of this function used to depend on dev->hdr_type.  Now
we don't look at hdr_type at all, so we do the same thing for all
devices.

For example, for a CardBus device, we used to call pci_update_resource()
only for BAR 0; now we call it for BARs 0-6.

Maybe this is safe, but I can't tell from the patch, so I think you
should explain *why* it's safe in the changelog.

> +/*
> + *  For PCI devices, the region numbers are assigned this way:
> + */
> +enum {
> +	/* #0-5: standard PCI regions */
> +	PCI_STD_RESOURCES,
> +	PCI_STD_RESOURCES_END = 5,
> +
> +	/* #6: expansion ROM */
> +	PCI_ROM_RESOURCE,
> +
> +	/* address space assigned to buses behind the bridge */
> +#ifndef PCI_BRIDGE_RES_NUM
> +#define PCI_BRIDGE_RES_NUM 4
> +#endif
> +	PCI_BRIDGE_RESOURCES,
> +	PCI_BRIDGE_RES_END = PCI_BRIDGE_RESOURCES + PCI_BRIDGE_RES_NUM - 1,

Since you used "PCI_STD_RESOURCES_END" above, maybe you should use
"PCI_BRIDGE_RESOURCES_END" instead of "PCI_BRIDGE_RES_END".

Bjorn
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