linux-kernel - Re: [PATCH v10 01/59] PCI: Add pci_find_root_bus

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Date:	Wed, 9 Mar 2016 21:54:15 -0600
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	David Miller <davem@...emloft.net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Wei Yang <weiyang@...ux.vnet.ibm.com>, TJ <linux@....tj>,
	Yijing Wang <wangyijing@...wei.com>,
	Khalid Aziz <khalid.aziz@...cle.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 01/59] PCI: Add pci_find_root_bus_resource()

On Wed, Feb 24, 2016 at 06:11:52PM -0800, Yinghai Lu wrote:
> Add pci_find_root_bus_resource() to return root bus resource
> for input resource.
> 
> For sparc mem64 support, We need that host bridge window res:
>   1. we need direct parent for request_resource_conflict() calling in
>       pci_register_legacy_regions().
>   2. check if return is NULL to decide if region is valid or not.

Whenever somebody proposes a new interface that's only required for
one architecture, the obvious question is "what is unique about that
architecture that makes the new interface necessary?"

Neither this patch nor the follow-on patch that adds the use of
pci_find_root_bus_resource() answers that question.

> Convert old pci_find_parent_resource() to pci_find_bus_resource(),
> and use it in pci_find_root_bus_resource() and new
> pci_find_parent_resource().
> 
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> ---
>  drivers/pci/pci.c   | 36 +++++++++++++++++++++++++-----------
>  include/linux/pci.h |  2 ++
>  2 files changed, 27 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 602eb42..db4025f 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -415,18 +415,9 @@ int pci_find_ht_capability(struct pci_dev *dev, int ht_cap)
>  }
>  EXPORT_SYMBOL_GPL(pci_find_ht_capability);
>  
> -/**
> - * pci_find_parent_resource - return resource region of parent bus of given region
> - * @dev: PCI device structure contains resources to be searched
> - * @res: child resource record for which parent is sought
> - *
> - *  For given resource region of given device, return the resource
> - *  region of parent bus the given region is contained in.
> - */
> -struct resource *pci_find_parent_resource(const struct pci_dev *dev,
> -					  struct resource *res)
> +static struct resource *pci_find_bus_resource(const struct pci_bus *bus,
> +					      struct resource *res)
>  {
> -	const struct pci_bus *bus = dev->bus;
>  	struct resource *r;
>  	int i;
>  
> @@ -456,8 +447,31 @@ struct resource *pci_find_parent_resource(const struct pci_dev *dev,
>  	}
>  	return NULL;
>  }
> +
> +/**
> + * pci_find_parent_resource - return resource region of parent bus of given region
> + * @dev: PCI device structure contains resources to be searched
> + * @res: child resource record for which parent is sought
> + *
> + *  For given resource region of given device, return the resource
> + *  region of parent bus the given region is contained in.
> + */
> +struct resource *pci_find_parent_resource(const struct pci_dev *dev,
> +					  struct resource *res)
> +{
> +	return pci_find_bus_resource(dev->bus, res);
> +}
>  EXPORT_SYMBOL(pci_find_parent_resource);
>  
> +struct resource *pci_find_root_bus_resource(struct pci_bus *bus,
> +					    struct resource *res)
> +{
> +	while (bus->parent)
> +		bus = bus->parent;
> +
> +	return pci_find_bus_resource(bus, res);
> +}
> +
>  /**
>   * pci_find_pcie_root_port - return PCIe Root Port
>   * @dev: PCI device to query
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 27df4a6..dd603a668 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -792,6 +792,8 @@ void pcibios_resource_to_bus(struct pci_bus *bus, struct pci_bus_region *region,
>  			     struct resource *res);
>  void pcibios_bus_to_resource(struct pci_bus *bus, struct resource *res,
>  			     struct pci_bus_region *region);
> +struct resource *pci_find_root_bus_resource(struct pci_bus *bus,
> +					    struct resource *res);
>  void pcibios_scan_specific_bus(int busn);
>  struct pci_bus *pci_find_bus(int domain, int busnr);
>  void pci_bus_add_devices(const struct pci_bus *bus);
> -- 
> 1.8.4.5
> 
> --
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