[PATCH] misc: Implement devm_misc_register

Gregory Fong
2017-05-09T02:27:55Z

Add device managed devm_misc_register() to allow simplifying some
miscdevice code.

Signed-off-by: Gregory Fong <gregory.fong@virginorbit.com>
---
This seemed like it would be handy for removing a large chunk of the cleanup
code in various miscdevice users. Let me know whether you think it'd be worth
going ahead changing this throughout the codebase where appropriate.

Documentation/driver-model/devres.txt | 5 ++++-
drivers/char/misc.c | 37 +++++++++++++++++++++++++++++++++++
include/linux/miscdevice.h | 2 ++
3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt
index bf34d5b..3b193f0 100644
--- a/Documentation/driver-model/devres.txt
+++ b/Documentation/driver-model/devres.txt
@@ -335,7 +335,10 @@ MEM
devm_kzalloc()

MFD
- devm_mfd_add_devices()
+ devm_mfd_add_devices()
+
+MISC
+ devm_misc_register()

PER-CPU MEM
devm_alloc_percpu()
diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index c9cd1ea..b7f653a 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -265,6 +265,43 @@ void misc_deregister(struct miscdevice *misc)
EXPORT_SYMBOL(misc_register);
EXPORT_SYMBOL(misc_deregister);

+static void devm_misc_dereg(struct device *dev, void *res)
+{
+ misc_deregister(*(struct miscdevice **)res);
+}
+
+/**
+ * devm_misc_register - Resource-managed misc_register
+ * @dev: Device to allocate miscdevice for
+ * @misc: Device structure filled by the device driver
+ *
+ * Managed misc_register. The miscdevice registered with this function is
+ * automatically unregistered on driver detach. This function calls
+ * misc_register() internally; refer to its documentation for more information.
+ *
+ * RETURNS:
+ * 0 on success, negative error number on failure.
+ */
+int devm_misc_register(struct device *dev, struct miscdevice *misc)
+{
+ struct miscdevice **misc_ptr;
+ int ret;
+
+ misc_ptr = devres_alloc(devm_misc_dereg, sizeof(*misc_ptr), GFP_KERNEL);
+ if (!misc_ptr)
+ return -ENOMEM;
+
+ *misc_ptr = misc;
+ ret = misc_register(misc);
+ if (!ret)
+ devres_add(dev, misc_ptr);
+ else
+ devres_free(misc_ptr);
+
+ return ret;
+}
+EXPORT_SYMBOL(devm_misc_register);
+
static char *misc_devnode(struct device *dev, umode_t *mode)
{
struct miscdevice *c = dev_get_drvdata(dev);
diff --git a/include/linux/miscdevice.h b/include/linux/miscdevice.h
index 762b5fe..5289b3f 100644
--- a/include/linux/miscdevice.h
+++ b/include/linux/miscdevice.h
@@ -74,6 +74,8 @@ struct miscdevice {
extern int misc_register(struct miscdevice *misc);
extern void misc_deregister(struct miscdevice *misc);

+int devm_misc_register(struct device *dev, struct miscdevice *misc);
+
/*
* Helper macro for drivers that don't do anything special in the initcall.
* This helps in eleminating of boilerplate code.
--
1.9.1