param: add kerneldoc to moduleparam.h

Also reorders the macros with the most common ones at the top.
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Reviewed-by: NTakashi Iwai <tiwai@suse.de>
Tested-by: NPhil Carmody <ext-phil.2.carmody@nokia.com>

include/linux/moduleparam.h

@@ -71,6 +71,62 @@ struct kparam_array
 	void *elem;
 };
 
+/**
+ * module_param - typesafe helper for a module/cmdline parameter
+ * @value: the variable to alter, and exposed parameter name.
+ * @type: the type of the parameter
+ * @perm: visibility in sysfs.
+ *
+ * @value becomes the module parameter, or (prefixed by KBUILD_MODNAME and a
+ * ".") the kernel commandline parameter.  Note that - is changed to _, so
+ * the user can use "foo-bar=1" even for variable "foo_bar".
+ *
+ * @perm is 0 if the the variable is not to appear in sysfs, or 0444
+ * for world-readable, 0644 for root-writable, etc.  Note that if it
+ * is writable, you may need to use kparam_block_sysfs_write() around
+ * accesses (esp. charp, which can be kfreed when it changes).
+ *
+ * The @type is simply pasted to refer to a param_ops_##type and a
+ * param_check_##type: for convenience many standard types are provided but
+ * you can create your own by defining those variables.
+ *
+ * Standard types are:
+ *	byte, short, ushort, int, uint, long, ulong
+ *	charp: a character pointer
+ *	bool: a bool, values 0/1, y/n, Y/N.
+ *	invbool: the above, only sense-reversed (N = true).
+ */
+#define module_param(name, type, perm)				\
+	module_param_named(name, name, type, perm)
+
+/**
+ * module_param_named - typesafe helper for a renamed module/cmdline parameter
+ * @name: a valid C identifier which is the parameter name.
+ * @value: the actual lvalue to alter.
+ * @type: the type of the parameter
+ * @perm: visibility in sysfs.
+ *
+ * Usually it's a good idea to have variable names and user-exposed names the
+ * same, but that's harder if the variable must be non-static or is inside a
+ * structure.  This allows exposure under a different name.
+ */
+#define module_param_named(name, value, type, perm)			   \
+	param_check_##type(name, &(value));				   \
+	module_param_cb(name, &param_ops_##type, &value, perm);		   \
+	__MODULE_PARM_TYPE(name, #type)
+
+/**
+ * module_param_cb - general callback for a module/cmdline parameter
+ * @name: a valid C identifier which is the parameter name.
+ * @ops: the set & get operations for this parameter.
+ * @perm: visibility in sysfs.
+ *
+ * The ops can have NULL set or get functions.
+ */
+#define module_param_cb(name, ops, arg, perm)				      \
+	__module_param_call(MODULE_PARAM_PREFIX,			      \
+			    name, ops, arg, __same_type(*(arg), bool), perm)
+
 /* On alpha, ia64 and ppc64 relocations to global data cannot go into
    read-only sections (which is part of respective UNIX ABI on these
    platforms). So 'const' makes no sense and even causes compile failures
@@ -82,9 +138,7 @@ struct kparam_array
 #endif
 
 /* This is the fundamental function for registering boot/module
-   parameters.  perm sets the visibility in sysfs: 000 means it's
-   not there, read bits mean it's readable, write bits mean it's
-   writable. */
+   parameters. */
 #define __module_param_call(prefix, name, ops, arg, isbool, perm)	\
 	/* Default value instead of permissions? */			\
 	static int __param_perm_check_##name __attribute__((unused)) =	\
@@ -113,23 +167,6 @@ __check_old_set_param(int (*oldset)(const char *, struct kernel_param *))
 	return 0;
 }
 
-#define module_param_cb(name, ops, arg, perm)				      \
-	__module_param_call(MODULE_PARAM_PREFIX,			      \
-			    name, ops, arg, __same_type(*(arg), bool), perm)
-
-/*
- * Helper functions: type is byte, short, ushort, int, uint, long,
- * ulong, charp, bool or invbool, or XXX if you define param_ops_XXX
- * and param_check_XXX.
- */
-#define module_param_named(name, value, type, perm)			   \
-	param_check_##type(name, &(value));				   \
-	module_param_cb(name, &param_ops_##type, &value, perm);		   \
-	__MODULE_PARM_TYPE(name, #type)
-
-#define module_param(name, type, perm)				\
-	module_param_named(name, name, type, perm)
-
 /**
  * kparam_block_sysfs_write - make sure a parameter isn't written via sysfs.
  * @name: the name of the parameter
@@ -191,7 +228,7 @@ static inline void __kernel_param_unlock(void)
  * core_param - define a historical core kernel parameter.
  * @name: the name of the cmdline and sysfs parameter (often the same as var)
  * @var: the variable
- * @type: the type (for param_set_##type and param_get_##type)
+ * @type: the type of the parameter
  * @perm: visibility in sysfs
  *
  * core_param is just like module_param(), but cannot be modular and
@@ -205,7 +242,16 @@ static inline void __kernel_param_unlock(void)
 			    &var, __same_type(var, bool), perm)
 #endif /* !MODULE */
 
-/* Actually copy string: maxlen param is usually sizeof(string). */
+/**
+ * module_param_string - a char array parameter
+ * @name: the name of the parameter
+ * @string: the string variable
+ * @len: the maximum length of the string, incl. terminator
+ * @perm: visibility in sysfs.
+ *
+ * This actually copies the string when it's set (unlike type charp).
+ * @len is usually just sizeof(string).
+ */
 #define module_param_string(name, string, len, perm)			\
 	static const struct kparam_string __param_string_##name		\
 		= { len, string };					\
@@ -294,7 +340,33 @@ extern int param_set_invbool(const char *val, const struct kernel_param *kp);
 extern int param_get_invbool(char *buffer, const struct kernel_param *kp);
 #define param_check_invbool(name, p) __param_check(name, p, bool)
 
-/* Comma-separated array: *nump is set to number they actually specified. */
+/**
+ * module_param_array - a parameter which is an array of some type
+ * @name: the name of the array variable
+ * @type: the type, as per module_param()
+ * @nump: optional pointer filled in with the number written
+ * @perm: visibility in sysfs
+ *
+ * Input and output are as comma-separated values.  Commas inside values
+ * don't work properly (eg. an array of charp).
+ *
+ * ARRAY_SIZE(@name) is used to determine the number of elements in the
+ * array, so the definition must be visible.
+ */
+#define module_param_array(name, type, nump, perm)		\
+	module_param_array_named(name, name, type, nump, perm)
+
+/**
+ * module_param_array_named - renamed parameter which is an array of some type
+ * @name: a valid C identifier which is the parameter name
+ * @array: the name of the array variable
+ * @type: the type, as per module_param()
+ * @nump: optional pointer filled in with the number written
+ * @perm: visibility in sysfs
+ *
+ * This exposes a different name than the actual variable name.  See
+ * module_param_named() for why this might be necessary.
+ */
 #define module_param_array_named(name, array, type, nump, perm)		\
 	static const struct kparam_array __param_arr_##name		\
 	= { ARRAY_SIZE(array), nump, &param_ops_##type,			\
@@ -305,9 +377,6 @@ extern int param_get_invbool(char *buffer, const struct kernel_param *kp);
 			    __same_type(array[0], bool), perm);		\
 	__MODULE_PARM_TYPE(name, "array of " #type)
 
-#define module_param_array(name, type, nump, perm)		\
-	module_param_array_named(name, name, type, nump, perm)
-
 extern struct kernel_param_ops param_array_ops;
 
 extern struct kernel_param_ops param_ops_string;