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Subject: Re: [PATCH v6 01/11] moduleparam: add data member to struct
 kernel_param
To:     Jim Cromie <jim.cromie@gmail.com>, gregkh@linuxfoundation.org,
        seanpaul@chromium.org, jeyu@kernel.org,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        amd-gfx@lists.freedesktop.org, intel-gvt-dev@lists.freedesktop.org,
        intel-gfx@lists.freedesktop.org
References: <20210822222009.2035788-1-jim.cromie@gmail.com>
 <20210822222009.2035788-2-jim.cromie@gmail.com>
From:   Jason Baron <jbaron@akamai.com>
Message-ID: <c83b0814-b8e1-91f5-ba28-f9db3f363ce1@akamai.com>
Date:   Wed, 25 Aug 2021 13:12:58 -0400
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On 8/22/21 6:19 PM, Jim Cromie wrote:
> Add a const 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_cb_data() derives from module_param_cb(), adding data
> param, and latter is redefined to use former.
> 
> It calls __module_param_call_with_data(), which accepts new data param
> and inits .data with it. Re-define __module_param_call() to use it.
> 
> Use of this new data member will be rare, it might be worth redoing
> this as a separate/sub-type to de-bloat the base case.
> 
> Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
> ---
> v6:
> . const void* data - <emil.l.velikov@gmail.com>
> . better macro names s/_cbd/_cb_data/, s/_wdata/_with_data/
> . more const, no cast - Willy
> ---
>  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..b8871e514de5 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;
>  	};
> +	const void *data;
>  };
>  


I wonder if kp->arg can just be used for all this and avoid this patch entirely?

define something like:

struct dd_bitmap_param {
	int bitmap;
	struct dyndbg_bitdesc *bitmap_arr;
};

and then just pass a pointer to it as 'arg' for module_param_cb? And then in
the get/set callbacks you can use kp->bitmap and kp->bitmap_arr.

Thanks,

-Jason

>  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_cb_data(name, ops, arg, perm, data)			\
> +	__module_param_call_with_data(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_with_data(prefix, name, ops, arg, perm, level, flags, NULL)
> +
> +#define __module_param_call_with_data(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)			\
>