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    SubjectRe: [RFC PATCH 1/9] cxl/acpi: Add an acpi_cxl module for the CXL interconnect
    On Tue, Nov 10, 2020 at 09:43:48PM -0800, Ben Widawsky wrote:
    > +menuconfig CXL_BUS
    > + tristate "CXL (Compute Express Link) Devices Support"
    > + help
    > + CXL is a bus that is electrically compatible with PCI-E, but layers
    > + three protocols on that signalling (CXL.io, CXL.cache, and CXL.mem). The
    > + CXL.cache protocol allows devices to hold cachelines locally, the
    > + CXL.mem protocol allows devices to be fully coherent memory targets, the
    > + CXL.io protocol is equivalent to PCI-E. Say 'y' to enable support for
    > + the configuration and management of devices supporting these protocols.
    > +

    Please fix the overly long lines.

    > +static void acpi_cxl_desc_init(struct acpi_cxl_desc *acpi_desc, struct device *dev)


    Another overly long line.

    > +{
    > + dev_set_drvdata(dev, acpi_desc);
    > + acpi_desc->dev = dev;
    > +}

    But this helper seems pretty pointless to start with.

    > +static int acpi_cxl_remove(struct acpi_device *adev)
    > +{
    > + return 0;
    > +}

    The emptry remove callback is not needed.

    > +/*
    > + * If/when CXL support is defined by other platform firmware the kernel
    > + * will need a mechanism to select between the platform specific version
    > + * of this routine, until then, hard-code ACPI assumptions
    > + */
    > +int cxl_bus_prepared(struct pci_dev *pdev)
    > +{
    > + struct acpi_device *adev;
    > + struct pci_dev *root_port;
    > + struct device *root;
    > +
    > + root_port = pcie_find_root_port(pdev);
    > + if (!root_port)
    > + return -ENXIO;
    > +
    > + root = root_port->dev.parent;
    > + if (!root)
    > + return -ENXIO;
    > +
    > + adev = ACPI_COMPANION(root);
    > + if (!adev)
    > + return -ENXIO;
    > +
    > + /* TODO: OSC enabling */
    > +
    > + return 0;
    > +}
    > +EXPORT_SYMBOL_GPL(cxl_bus_prepared);

    What is the point of this function? I doesn't realy do anything,
    not even a CXL specific check.

    >
    > +/*******************************************************************************
    > + *
    > + * CEDT - CXL Early Discovery Table (ACPI 6.4)
    > + * Version 1
    > + *
    > + ******************************************************************************/
    > +

    Pleae use the normal Linux comment style.


    > +#define ACPI_CEDT_CHBS_VERSION_CXL11 (0)
    > +#define ACPI_CEDT_CHBS_VERSION_CXL20 (1)
    > +
    > +/* Values for length field above */
    > +
    > +#define ACPI_CEDT_CHBS_LENGTH_CXL11 (0x2000)
    > +#define ACPI_CEDT_CHBS_LENGTH_CXL20 (0x10000)

    No need for the braces.

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