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Subject[PATCH v2] 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>
---
Changes in v2:
- properly pass around the owner module

Documentation/driver-model/platform.txt | 14 ++++++++
drivers/base/platform.c | 61 +++++++++++++++++++++++++++++++++
include/linux/platform_device.h | 8 +++++
3 files changed, 83 insertions(+)

diff --git a/Documentation/driver-model/platform.txt b/Documentation/driver-model/platform.txt
index 07795ec51cde..e456696cfef2 100644
--- a/Documentation/driver-model/platform.txt
+++ b/Documentation/driver-model/platform.txt
@@ -63,6 +63,20 @@ 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, struct module *owner);
+ 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. Note that there is a convenience
+macro that passes THIS_MODULE as owner parameter:
+
+ #define platform_register_driver(drivers, count)
+

Device Enumeration
~~~~~~~~~~~~~~~~~~
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index f80aaaf9f610..68c58c43e45a 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -711,6 +711,67 @@ 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
+ * @owner: module owning the drivers
+ *
+ * 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, struct module *owner)
+{
+ 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], owner);
+ 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..dc777be5f2e1 100644
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -270,6 +270,14 @@ 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, struct module *owner);
+void platform_unregister_drivers(struct platform_driver * const *drivers,
+ unsigned int count);
+
+#define platform_register_drivers(drivers, count) \
+ __platform_register_drivers(drivers, count, THIS_MODULE)
+
/* early platform driver interface */
struct early_platform_driver {
const char *class_str;
--
2.5.0


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