linux-kernel - Re: [PATCH 1/4] PCI / ACPI: Identify external PCI devices

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Message-ID: <20181112180203.lx72gjfplb6xlur7@wunner.de>
Date:   Mon, 12 Nov 2018 19:02:03 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     iommu@...ts.linux-foundation.org, Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>,
        Christian Kellner <ckellner@...hat.com>,
        Mario.Limonciello@...l.com,
        Anthony Wong <anthony.wong@...onical.com>,
        linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] PCI / ACPI: Identify external PCI devices

On Mon, Nov 12, 2018 at 07:06:25PM +0300, Mika Westerberg wrote:
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1378,6 +1378,27 @@ static void set_pcie_thunderbolt(struct pci_dev *dev)
>  	}
>  }
>  
> +static void set_pcie_external(struct pci_dev *dev)
> +{
> +	struct pci_dev *parent;
> +
> +	/*
> +	 * Walk up the device hierarchy and check for any upstream
> +	 * bridge that has is_external_facing set to true. This means
> +	 * the hierarchy is below PCIe port that is exposed externally
> +	 * (such as Thunderbolt).
> +	 */
> +	parent = pci_upstream_bridge(dev);
> +	while (parent) {
> +		if (parent->is_external) {
> +			dev->is_external = true;
> +			break;
> +		}
> +
> +		parent = pci_upstream_bridge(parent);
> +	}
> +}
> +

This looks pretty much like a duplication of the is_thunderbolt bit
in struct pci_dev and the pci_is_thunderbolt_attached() helper.

Why constrain the functionality to ports with the _DSD property
instead of making it available for *any* Thunderbolt port?

Thanks,

Lukas