Re: [PATCH 2/8] param: use ops in struct kernel_param, rather than get and set fns directly

Re: [PATCH 2/8] param: use ops in struct kernel_param, rather than get and set fns directly

[Takashi Iwai]

At Fri, 23 Oct 2009 00:51:28 +1030,
Rusty Russell wrote:
> 
> This is more kernel-ish, saves some space, and also allows us to
> expand the ops without breaking all the callers who are happy for the
> new members to be NULL.
> 
> The few places which defined their own param types are changed to the
> new scheme.
> 
> Since we're touching them anyway, we change get and set to take a
> const struct kernel_param (which they were, and will be again).
> 
> To reduce churn, module_param_call creates the ops struct so the callers
> don't have to change (and casts the functions to reduce warnings).
> The modern version which takes an ops struct is called module_param_cb.

This is nice, as it also reduces the size of struct kernel_param, so
each parameter uses less footprint (who cares, though?) :)

But, just wondering whether we still need to export get/set
functions.  They can be called from ops now, so if any, it can be
defined even as an inlinefunction or a macro.


thanks,

Takashi

Re: [PATCH 2/8] param: use ops in struct kernel_param, rather than get and set fns directly

[Rusty Russell]

On Fri, 30 Oct 2009 08:48:12 pm Takashi Iwai wrote:
> At Fri, 23 Oct 2009 00:51:28 +1030,
> Rusty Russell wrote:
> > 
> > This is more kernel-ish, saves some space, and also allows us to
> > expand the ops without breaking all the callers who are happy for the
> > new members to be NULL.
> > 
> > The few places which defined their own param types are changed to the
> > new scheme.
> > 
> > Since we're touching them anyway, we change get and set to take a
> > const struct kernel_param (which they were, and will be again).
> > 
> > To reduce churn, module_param_call creates the ops struct so the callers
> > don't have to change (and casts the functions to reduce warnings).
> > The modern version which takes an ops struct is called module_param_cb.
> 
> This is nice, as it also reduces the size of struct kernel_param, so
> each parameter uses less footprint (who cares, though?) :)
> 
> But, just wondering whether we still need to export get/set
> functions.  They can be called from ops now, so if any, it can be
> defined even as an inlinefunction or a macro.

My thought too, so I tried that, but many are still used like so:

	module_param_call(foo, set_foo, param_get_uint, NULL, 0644);

They can all be replaced in time with something like:
	static int param_get_foo(char *buffer, const struct kernel_param *kp)
	{
		return param_ops_uint.get(buffer, kp);
	}

But it'll take a transition period.

Thanks!
Rusty.



> 
> 
> thanks,
> 
> Takashi
> 
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Re: [PATCH 2/8] param: use ops in struct kernel_param, rather than get and set fns directly

[Takashi Iwai]

At Fri, 30 Oct 2009 21:43:39 +1030,
Rusty Russell wrote:
> 
> On Fri, 30 Oct 2009 08:48:12 pm Takashi Iwai wrote:
> > At Fri, 23 Oct 2009 00:51:28 +1030,
> > Rusty Russell wrote:
> > > 
> > > This is more kernel-ish, saves some space, and also allows us to
> > > expand the ops without breaking all the callers who are happy for the
> > > new members to be NULL.
> > > 
> > > The few places which defined their own param types are changed to the
> > > new scheme.
> > > 
> > > Since we're touching them anyway, we change get and set to take a
> > > const struct kernel_param (which they were, and will be again).
> > > 
> > > To reduce churn, module_param_call creates the ops struct so the callers
> > > don't have to change (and casts the functions to reduce warnings).
> > > The modern version which takes an ops struct is called module_param_cb.
> > 
> > This is nice, as it also reduces the size of struct kernel_param, so
> > each parameter uses less footprint (who cares, though?) :)
> > 
> > But, just wondering whether we still need to export get/set
> > functions.  They can be called from ops now, so if any, it can be
> > defined even as an inlinefunction or a macro.
> 
> My thought too, so I tried that, but many are still used like so:
> 
> 	module_param_call(foo, set_foo, param_get_uint, NULL, 0644);
> 
> They can all be replaced in time with something like:
> 	static int param_get_foo(char *buffer, const struct kernel_param *kp)
> 	{
> 		return param_ops_uint.get(buffer, kp);
> 	}
> 
> But it'll take a transition period.

Fair enough.  And, maybe these get/set should be defined as an ops
explicitly so that it can be used for multiple parameters.  But we
can do cleanups later, of course :)

Oh, in case you need,
	Reviewed-by: Takashi Iwai <tiwai@suse.de>
for all new patches.


Thanks!

Takashi