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SubjectRe: [PATCH 1/6] driver-core: platform: Provide helpers for multi-driver modules
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On Thu, 24 Sep 2015, Thierry Reding <thierry.reding@gmail.com> wrote:
> 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]);
> + }

This will call platform_driver_unregister() on the driver that failed,
but not the first driver.

You should probably make i an int, and use while (--i >= 0).

BR,
Jani.

> +
> + 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
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

--
Jani Nikula, Intel Open Source Technology Center


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