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From:   Jim Cromie <jim.cromie@gmail.com>
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Subject: [PATCH v4 2/7] moduleparam: add data member to struct kernel_param
Date:   Sat, 31 Jul 2021 15:41:59 -0600
Message-Id: <20210731214211.657280-3-jim.cromie@gmail.com>
In-Reply-To: <20210731214211.657280-1-jim.cromie@gmail.com>
References: <20210731214211.657280-1-jim.cromie@gmail.com>
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Add a void* data member to the struct, to allow attaching private data
that will be used soon by a setter method (via kp->data) to perform
more elaborate actions.

To attach the data at compile time, add new macros:
module_param_cbd() derives from module_param_cb(), adding data param.
It calls __module_param_call_wdata(), which has accepts new data
param and inits .data with it. Re-define __module_param_call() using it.

Use of this new data member will be rare, it might be worth redoing
this as a separate/sub-type to keep the base case.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 include/linux/moduleparam.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index eed280fae433..e9495b1e794d 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -78,6 +78,7 @@ struct kernel_param {
 		const struct kparam_string *str;
 		const struct kparam_array *arr;
 	};
+	void *data;
 };
 
 extern const struct kernel_param __start___param[], __stop___param[];
@@ -175,6 +176,9 @@ struct kparam_array
 #define module_param_cb(name, ops, arg, perm)				      \
 	__module_param_call(MODULE_PARAM_PREFIX, name, ops, arg, perm, -1, 0)
 
+#define module_param_cbd(name, ops, arg, perm, data)				\
+	__module_param_call_wdata(MODULE_PARAM_PREFIX, name, ops, arg, perm, -1, 0, data)
+
 #define module_param_cb_unsafe(name, ops, arg, perm)			      \
 	__module_param_call(MODULE_PARAM_PREFIX, name, ops, arg, perm, -1,    \
 			    KERNEL_PARAM_FL_UNSAFE)
@@ -284,14 +288,17 @@ struct kparam_array
 
 /* This is the fundamental function for registering boot/module
    parameters. */
-#define __module_param_call(prefix, name, ops, arg, perm, level, flags)	\
+#define __module_param_call(prefix, name, ops, arg, perm, level, flags) \
+	__module_param_call_wdata(prefix, name, ops, arg, perm, level, flags, NULL)
+
+#define __module_param_call_wdata(prefix, name, ops, arg, perm, level, flags, data) \
 	/* Default value instead of permissions? */			\
 	static const char __param_str_##name[] = prefix #name;		\
 	static struct kernel_param __moduleparam_const __param_##name	\
 	__used __section("__param")					\
 	__aligned(__alignof__(struct kernel_param))			\
 	= { __param_str_##name, THIS_MODULE, ops,			\
-	    VERIFY_OCTAL_PERMISSIONS(perm), level, flags, { arg } }
+	    VERIFY_OCTAL_PERMISSIONS(perm), level, flags, { arg }, data }
 
 /* Obsolete - use module_param_cb() */
 #define module_param_call(name, _set, _get, arg, perm)			\
-- 
2.31.1