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    SubjectRe: [PATCH 07/15] cxl/acpi: Check RCH's PCIe Host Bridge ACPI ID
    On Wed, 31 Aug 2022 10:15:55 +0200
    Robert Richter <rrichter@amd.com> wrote:

    > An RCH is a root bridge and has "PNP0A08" or "ACPI0016" ACPI ID set.
    > Check this.
    >
    > Signed-off-by: Robert Richter <rrichter@amd.com>

    Hi Robert,

    I'm a little uncomfortable with repurposing acpi_device_id
    as you have done here. Might be better to do the same
    as in pci_root.c where the matches are done more directly.

    > ---
    > drivers/cxl/acpi.c | 20 ++++++++++++++++++++
    > 1 file changed, 20 insertions(+)
    >
    > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
    > index a19e3154dd44..ffdf439adb87 100644
    > --- a/drivers/cxl/acpi.c
    > +++ b/drivers/cxl/acpi.c
    > @@ -312,9 +312,16 @@ static int add_root_nvdimm_bridge(struct device *match, void *data)
    > return 1;
    > }
    >
    > +static const struct acpi_device_id cxl_host_ids[] = {
    > + { "ACPI0016", 0 },
    > + { "PNP0A08", 0 },
    > + { },

    Trivial but no comma after a null terminator. Always good to make
    it harder for people to add things where they really shouldn't!

    pci_root.c avoids using an acpi_device_id table for similar matching.
    I think the point being to separate probe type use of this table
    from cases where we aren't using a normal device probe.
    So to remain consistent with that, I would just grab the hid
    and match it directly in this code.

    I don't feel that strongly about this if the ACPI maintainers are
    fine with reusing this infrastructure as you have it here.


    > +};
    > +
    > struct pci_host_bridge *cxl_find_next_rch(struct pci_host_bridge *host)
    > {
    > struct pci_bus *bus = host ? host->bus : NULL;
    > + struct acpi_device *adev;
    >
    > while ((bus = pci_find_next_bus(bus)) != NULL) {
    > host = bus ? to_pci_host_bridge(bus->bridge) : NULL;
    > @@ -323,6 +330,19 @@ struct pci_host_bridge *cxl_find_next_rch(struct pci_host_bridge *host)
    >
    > dev_dbg(&host->dev, "PCI bridge found\n");
    >
    > + /* Must be a root bridge */
    > + if (host->bus->parent)
    > + continue;
    > +
    > + dev_dbg(&host->dev, "PCI bridge is root bridge\n");
    > +
    > + adev = ACPI_COMPANION(&host->dev);
    > + if (acpi_match_device_ids(adev, cxl_host_ids))
    > + continue;
    > +
    > + dev_dbg(&host->dev, "PCI ACPI host found: %s\n",
    > + acpi_dev_name(adev));
    > +
    > return host;
    > }
    >

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