linux-kernel - Re: [PATCH 03/14] pci: add pci_bridge_release_unused_res and pci_bus_release_unused_bridge

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Date:	Fri, 15 Jan 2010 16:20:14 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
CC:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	Alex Chiang <achiang@...com>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 03/14] pci: add pci_bridge_release_unused_res and pci_bus_release_unused_bridge_res

On 01/15/2010 10:53 AM, Jesse Barnes wrote:
> On Tue, 22 Dec 2009 15:02:23 -0800
> Yinghai Lu <yinghai@...nel.org> wrote:
>> +static void pci_bridge_release_unused_res(struct pci_bus *bus,
>> +					  unsigned long type)
>> +{
>> +	int idx;
>> +	bool changed = false;
>> +	struct pci_dev *dev;
>> +	struct resource *r;
>> +	unsigned long type_mask = IORESOURCE_IO | IORESOURCE_MEM |
>> +				  IORESOURCE_PREFETCH;
>> +
>> +	dev = bus->self;
>> +	for (idx = PCI_BRIDGE_RESOURCES; idx <=
>> PCI_BRIDGE_RESOURCE_END;
>> +	     idx++) {
>> +		r = &dev->resource[idx];
>> +		if ((r->flags & type_mask) != type)
>> +			continue;
>> +		if (!r->parent)
>> +			continue;
>> +		/*
>> +		 * if there are children under that, we should
>> release them
>> +		 *  all
>> +		 */
>> +		release_child_resources(r);
>> +		if (!release_resource(r)) {
>> +			dev_printk(KERN_DEBUG, &dev->dev,
>> +				 "resource %d %pR released\n", idx,
>> r);
>> +			/* keep the old size */
>> +			r->end = resource_size(r) - 1;
>> +			r->start = 0;
>> +			r->flags = 0;
>> +			changed = true;
>> +		}
>> +	}
>> +
>> +	if (changed) {
>> +		if (type & IORESOURCE_PREFETCH) {
>> +			/* avoiding touch the one without PREF */
>> +			type = IORESOURCE_PREFETCH;
>> +		}
>> +		__pci_setup_bridge(bus, type);
>> +	}
>> +}
> 
> Isn't this freeing resources regardless of whether there are children?
> If so, shouldn't it just be called pci_bridge_release_resources?
> 
ok
>> +
>> +/*
>> + * try to release pci bridge resources that is from leaf bridge,
>> + * so we can allocate big new one later
>> + * check:
>> + *    0: only release the bridge and only the bridge is leaf
>> + *    1: release all down side bridge for third shoot
>> + */
>> +static void __ref pci_bus_release_unused_bridge_res(struct pci_bus
>> *bus,
>> +						    unsigned long
>> type,
>> +						    int check_leaf)
>> +{
>> +	struct pci_dev *dev;
>> +	bool is_leaf_bridge = true;
>> +
>> +	list_for_each_entry(dev, &bus->devices, bus_list) {
>> +		struct pci_bus *b = dev->subordinate;
>> +		if (!b)
>> +			continue;
>> +
>> +		switch (dev->class >> 8) {
>> +		case PCI_CLASS_BRIDGE_CARDBUS:
>> +			is_leaf_bridge = false;
>> +			break;
>> +
>> +		case PCI_CLASS_BRIDGE_PCI:
>> +		default:
>> +			is_leaf_bridge = false;
>> +			if (!check_leaf)
>> +				pci_bus_release_unused_bridge_res(b,
>> type,
>> +							 check_leaf);
>> +			break;
>> +		}
>> +	}
>> +
>> +	/* The root bus? */
>> +	if (!bus->self)
>> +		return;
>> +
>> +	switch (bus->self->class >> 8) {
>> +	case PCI_CLASS_BRIDGE_CARDBUS:
>> +		break;
>> +
>> +	case PCI_CLASS_BRIDGE_PCI:
>> +	default:
>> +		if ((check_leaf && is_leaf_bridge) || !check_leaf)
>> +			pci_bridge_release_unused_res(bus, type);
>> +		break;
>> +	}
>> +}
> 
> Naming comment applies here too.  I'd also rather see the "check_leaf"
> flag be an enum, that makes the callers more self documenting.  The
> enums should probably be called "leaf_only" and "whole_subtree" or
> similar , since the function will only release the resources of a leaf
> bridge when the former is passed, while the whole bridge and its
> subtree will be released in the latter case.
ok

YH
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