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From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Yicong Yang <yangyicong@hisilicon.com>
Cc: Bjorn Helgaas <helgaas@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Kalle Valo <kvalo@codeaurora.org>,
	linux-pci@vger.kernel.org
Subject: Re: [PATCH] PCI: Make pcie_find_root_port() work for PCIe root ports as well
Date: Wed, 1 Jul 2020 13:15:41 +0300
Message-ID: <20200701101541.GO5180@lahna.fi.intel.com> (raw)
In-Reply-To: <c4282c55-8312-53a0-d9e6-4818b9206c1f@hisilicon.com>

On Wed, Jul 01, 2020 at 09:53:51AM +0800, Yicong Yang wrote:
> >  static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
> >  {
> > -	struct pci_dev *bridge = pci_upstream_bridge(dev);
> > -
> > -	while (bridge) {
> > -		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
> > -			return bridge;
> > -		bridge = pci_upstream_bridge(bridge);
> > +	while (dev) {
> > +		if (pci_is_pcie(dev) &&
> > +		    pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
> > +			return dev;
> > +		dev = pci_upstream_bridge(dev);
> >  	}
> >  
> 
> We may have some problems here, as after pcie_find_root_port() called, *dev will
> be either root port or NULL but users may want it unchanged. One such usage is
> in acpi_pci_bridge_d3(), drivers/pci/pci-acpi.c, *dev is used as origin
> after called this.
> 
> So we should use a temporary point to *dev rather than directly modify it.

dev is already a copy of what is passed by the caller so it does not
matter if it gets changed here. You would need to pass it through struct
pci_dev **dev in order to modify the passed pointer.

  reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-22 16:12 Mika Westerberg
2020-06-30 22:01 ` Bjorn Helgaas
2020-07-01  1:53   ` Yicong Yang
2020-07-01 10:15     ` Mika Westerberg [this message]
2020-07-01 12:47       ` Yicong Yang
2020-07-01 10:14   ` Mika Westerberg

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