Re: [PATCH] drivers/net/pcmcia: use module_param() instead of MODULE_PARM()

[Randy.Dunlap]

Stelian Pop wrote:
> On Wed, Nov 10, 2004 at 08:35:05AM -0800, Randy.Dunlap wrote:
>
>
> > Hi Stelian,
>
>
> Hi.
>
> > Several of these changes expose module parameters to sysfs
> > (i.e., have permissions of non-zero value) without need for that IMO.
> >
> > This came up yesterday on the kernel-janitors mailing list.
> > When asked about it, Greg KH replied:
>
>
> :)
>
> I shouldn't probably discuss Greg's advice, but...

AFAIK, you are free to disagree as long as I or we can also
disagree.  :)

> > > Can someone please clarify the "official guidelines" for
> > > module parameter permissions in sysfs?
> >
> > "When it makes sense to have it exposed to userspace"
> >
> > Yeah, it's vague, sorry, but it all depends.
> >
> > For things that can be changed on the fly, expose it.
>
>
> ... with a write permission. Agreed.
>
>
> > For things that don't really matter, and no one will ever look them up,
> > don't. 
> > I think the irq stuff is in the "don't" category, as almost no
> > one messes with them anymore.
>
>
> In this case why is this a module parameter at all ? If it doesn't
> matter at all then it should get removed from all places.
>
> In fact, I do think that all module parameter should be exposed in
> /sys, and that a '0' in module_param() should really mean 0400.
>
> It can be useful to know what parameters have been passed to a module,
> and I cannot think of a single case where we want to hide this 
> information (and no, security doesn't really apply here. If you have
> root rights than you can also look into the kernel memory and find
> out the value by yourself).
>
> The only questions one should ask himself about a module parameter is
> whether:
> 	- it is a R/O or a R/W value (and this is determined by
> 	  the code who uses this value, if it is dynamic then let
> 	  the parameter be R/W, if it's only used to make assumptions
> 	  in the init phase then it must be R/O).
>
> 	- it can be shown to everybody, or only root should be able
> 	  to read the value (0400 vs 0440/0444). I'm not sure this is
> 	  really useful since /etc/modprobe.conf is generaly 0644,
> 	  but it could be in some cases...

I don't have an argument with most of that, but I am concerned
about how much memory each entry requires and how useful it really
is.  IOW, if I need to know the module parameters for a module,
I can probably find that info somewhere else, like in
/etc/modprobe.conf or a script etc., so why waste memory on it?

But then there's the question of if someone else needs to know
the module parameters that were used, where do they look?
I could say:  same answer as I gave above.
Or you could say:  exposed in /sys.
If memory usage is not an issue, I'll agree.

--
~Randy
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