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    Subject[PATCH 1/6] driver-core: platform: Provide helpers for multi-driver modules
    Date
    From: Thierry Reding <treding@nvidia.com>

    Some modules register several sub-drivers. Provide a helper that makes
    it easy to register and unregister a list of sub-drivers, as well as
    unwind properly on error.

    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Thierry Reding <treding@nvidia.com>
    ---
    Documentation/driver-model/platform.txt | 11 ++++++
    drivers/base/platform.c | 60 +++++++++++++++++++++++++++++++++
    include/linux/platform_device.h | 5 +++
    3 files changed, 76 insertions(+)

    diff --git a/Documentation/driver-model/platform.txt b/Documentation/driver-model/platform.txt
    index 07795ec51cde..e80468738ba9 100644
    --- a/Documentation/driver-model/platform.txt
    +++ b/Documentation/driver-model/platform.txt
    @@ -63,6 +63,17 @@ runtime memory footprint:
    int platform_driver_probe(struct platform_driver *drv,
    int (*probe)(struct platform_device *))

    +Kernel modules can be composed of several platform drivers. The platform core
    +provides helpers to register and unregister an array of drivers:
    +
    + int platform_register_drivers(struct platform_driver * const *drivers,
    + unsigned int count);
    + void platform_unregister_drivers(struct platform_driver * const *drivers,
    + unsigned int count);
    +
    +If one of the drivers fails to register, all drivers registered up to that
    +point will be unregistered in reverse order.
    +

    Device Enumeration
    ~~~~~~~~~~~~~~~~~~
    diff --git a/drivers/base/platform.c b/drivers/base/platform.c
    index f80aaaf9f610..b7d7987fda97 100644
    --- a/drivers/base/platform.c
    +++ b/drivers/base/platform.c
    @@ -711,6 +711,66 @@ err_out:
    }
    EXPORT_SYMBOL_GPL(__platform_create_bundle);

    +/**
    + * platform_register_drivers - register an array of platform drivers
    + * @drivers: an array of drivers to register
    + * @count: the number of drivers to register
    + *
    + * Registers platform drivers specified by an array. On failure to register a
    + * driver, all previously registered drivers will be unregistered. Callers of
    + * this API should use platform_unregister_drivers() to unregister drivers in
    + * the reverse order.
    + *
    + * Returns: 0 on success or a negative error code on failure.
    + */
    +int platform_register_drivers(struct platform_driver * const *drivers,
    + unsigned int count)
    +{
    + unsigned int i;
    + int err;
    +
    + for (i = 0; i < count; i++) {
    + pr_debug("registering platform driver %ps\n", drivers[i]);
    +
    + err = platform_driver_register(drivers[i]);
    + if (err < 0) {
    + pr_err("failed to register platform driver %ps: %d\n",
    + drivers[i], err);
    + goto error;
    + }
    + }
    +
    + return 0;
    +
    +error:
    + while (i--) {
    + pr_debug("unregistering platform driver %ps\n", drivers[i]);
    + platform_driver_unregister(drivers[i]);
    + }
    +
    + return err;
    +}
    +EXPORT_SYMBOL_GPL(platform_register_drivers);
    +
    +/**
    + * platform_unregister_drivers - unregister an array of platform drivers
    + * @drivers: an array of drivers to unregister
    + * @count: the number of drivers to unregister
    + *
    + * Unegisters platform drivers specified by an array. This is typically used
    + * to complement an earlier call to platform_register_drivers(). Drivers are
    + * unregistered in the reverse order in which they were registered.
    + */
    +void platform_unregister_drivers(struct platform_driver * const *drivers,
    + unsigned int count)
    +{
    + while (count--) {
    + pr_debug("unregistering platform driver %ps\n", drivers[count]);
    + platform_driver_unregister(drivers[count]);
    + }
    +}
    +EXPORT_SYMBOL_GPL(platform_unregister_drivers);
    +
    /* modalias support enables more hands-off userspace setup:
    * (a) environment variable lets new-style hotplug events work once system is
    * fully running: "modprobe $MODALIAS"
    diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
    index bba08f44cc97..0c9f16bfdd99 100644
    --- a/include/linux/platform_device.h
    +++ b/include/linux/platform_device.h
    @@ -270,6 +270,11 @@ extern struct platform_device *__platform_create_bundle(
    struct resource *res, unsigned int n_res,
    const void *data, size_t size, struct module *module);

    +int platform_register_drivers(struct platform_driver * const *drivers,
    + unsigned int count);
    +void platform_unregister_drivers(struct platform_driver * const *drivers,
    + unsigned int count);
    +
    /* early platform driver interface */
    struct early_platform_driver {
    const char *class_str;
    --
    2.5.0


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