linux-kernel - [PATCH 1/2] uio: add resource managed devm_uio_register

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Date:   Fri, 6 Mar 2020 18:18:52 +0200
From:   Alexandru Ardelean <alexandru.ardelean@...log.com>
To:     <linux-kernel@...r.kernel.org>
CC:     <gregkh@...uxfoundation.org>,
        Alexandru Ardelean <alexandru.ardelean@...log.com>
Subject: [PATCH 1/2] uio: add resource managed devm_uio_register_device() function

This change adds a resource managed equivalent of uio_register_device().
Not adding devm_uio_unregister_device(), since the intent is to discourage
it's usage. Having such a function may allow some bad driver designs. Most
users of devm_*register*() functions rarely use the unregister equivalents.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
---
 drivers/uio/uio.c          | 38 ++++++++++++++++++++++++++++++++++++++
 include/linux/uio_driver.h |  9 +++++++++
 2 files changed, 47 insertions(+)

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index a57698985f9c..6e725c6c6256 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -996,6 +996,44 @@ int __uio_register_device(struct module *owner,
 }
 EXPORT_SYMBOL_GPL(__uio_register_device);
 
+static void devm_uio_unregister_device(struct device *dev, void *res)
+{
+	uio_unregister_device(*(struct uio_info **)res);
+}
+
+/**
+ * devm_uio_register_device - Resource managed uio_register_device()
+ * @owner:	module that creates the new device
+ * @parent:	parent device
+ * @info:	UIO device capabilities
+ *
+ * returns zero on success or a negative error code.
+ */
+int __devm_uio_register_device(struct module *owner,
+			       struct device *parent,
+			       struct uio_info *info)
+{
+	struct uio_info **ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_uio_unregister_device, sizeof(*ptr),
+			   GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	*ptr = info;
+	ret = __uio_register_device(owner, parent, info);
+	if (ret) {
+		devres_free(ptr);
+		return ret;
+	}
+
+	devres_add(parent, ptr);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__devm_uio_register_device);
+
 /**
  * uio_unregister_device - unregister a industrial IO device
  * @info:	UIO device capabilities
diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
index 01081c4726c0..c5a306bd458c 100644
--- a/include/linux/uio_driver.h
+++ b/include/linux/uio_driver.h
@@ -123,6 +123,15 @@ extern int __must_check
 extern void uio_unregister_device(struct uio_info *info);
 extern void uio_event_notify(struct uio_info *info);
 
+extern int __must_check
+	__devm_uio_register_device(struct module *owner,
+				   struct device *parent,
+				   struct uio_info *info);
+
+/* use a define to avoid include chaining to get THIS_MODULE */
+#define devm_uio_register_device(parent, info) \
+	__devm_uio_register_device(THIS_MODULE, parent, info)
+
 /* defines for uio_info->irq */
 #define UIO_IRQ_CUSTOM	-1
 #define UIO_IRQ_NONE	0
-- 
2.20.1