[PATCH 1/6] driver-core: platform: Provide helpers for multi-driver modules

[Thierry Reding]

From: Thierry Reding <treding at 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 at linuxfoundation.org>
Signed-off-by: Thierry Reding <treding at 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