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    Subject[PATCH 06/31] driver core: platform_bus: allow runtime override of dev_pm_ops
    Date
    From: Kevin Hilman <khilman@ti.com>

    Currently, the platform_bus allows customization of several of the
    busses dev_pm_ops methods by using weak symbols so that platform code
    can override them. The weak-symbol approach is not scalable when
    wanting to support multiple platforms in a single kernel binary.

    Instead, provide __init methods for platform code to customize the
    dev_pm_ops methods at runtime.

    NOTE: after these dynamic methods are merged, the weak symbols should
    be removed from drivers/base/platform.c. AFAIK, this will only
    affect SH and sh-mobile which should be converted to use this
    runtime approach instead of the weak symbols. After SH &
    sh-mobile are converted, the weak symobols could be removed.

    Tested on OMAP3.

    Cc: Magnus Damm <magnus.damm@gmail.com>
    Acked-by: Grant Likely <grant.likely@secretlab.ca>
    Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    drivers/base/platform.c | 35 +++++++++++++++++++++++++++++++++++
    include/linux/platform_device.h | 3 +++
    2 files changed, 38 insertions(+), 0 deletions(-)

    diff --git a/drivers/base/platform.c b/drivers/base/platform.c
    index 579906f..a01abf9 100644
    --- a/drivers/base/platform.c
    +++ b/drivers/base/platform.c
    @@ -976,6 +976,41 @@ struct bus_type platform_bus_type = {
    };
    EXPORT_SYMBOL_GPL(platform_bus_type);

    +/**
    + * platform_bus_get_pm_ops() - return pointer to busses dev_pm_ops
    + *
    + * This function can be used by platform code to get the current
    + * set of dev_pm_ops functions used by the platform_bus_type.
    + */
    +const struct dev_pm_ops * __init platform_bus_get_pm_ops(void)
    +{
    + return platform_bus_type.pm;
    +}
    +
    +/**
    + * platform_bus_set_pm_ops() - update dev_pm_ops for the platform_bus_type
    + *
    + * @pm: pointer to new dev_pm_ops struct to be used for platform_bus_type
    + *
    + * Platform code can override the dev_pm_ops methods of
    + * platform_bus_type by using this function. It is expected that
    + * platform code will first do a platform_bus_get_pm_ops(), then
    + * kmemdup it, then customize selected methods and pass a pointer to
    + * the new struct dev_pm_ops to this function.
    + *
    + * Since platform-specific code is customizing methods for *all*
    + * devices (not just platform-specific devices) it is expected that
    + * any custom overrides of these functions will keep existing behavior
    + * and simply extend it. For example, any customization of the
    + * runtime PM methods should continue to call the pm_generic_*
    + * functions as the default ones do in addition to the
    + * platform-specific behavior.
    + */
    +void __init platform_bus_set_pm_ops(const struct dev_pm_ops *pm)
    +{
    + platform_bus_type.pm = pm;
    +}
    +
    int __init platform_bus_init(void)
    {
    int error;
    diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
    index d7ecad0..2e700ec 100644
    --- a/include/linux/platform_device.h
    +++ b/include/linux/platform_device.h
    @@ -138,6 +138,9 @@ extern struct platform_device *platform_create_bundle(struct platform_driver *dr
    struct resource *res, unsigned int n_res,
    const void *data, size_t size);

    +extern const struct dev_pm_ops * platform_bus_get_pm_ops(void);
    +extern void platform_bus_set_pm_ops(const struct dev_pm_ops *pm);
    +
    /* early platform driver interface */
    struct early_platform_driver {
    const char *class_str;
    --
    1.7.2


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