[PATCH 13/13] fix ps3fb glue allowing a modular build

[Linus Torvalds]

On Wed, 14 Mar 2007, Al Viro wrote:
> 
> Nope.  How can kconfig distinguish that from a boolean option in modular
> driver?  bool *can* depend on tristate and be selected when tristate is
> set to m.

Btw, this is one of those things that easily causes problems.

In many ways it would be nice if we had two different kinds of "bool": one 
where "m" in the dependency chain means "y" is ok, and one where "m" means 
"n".

We used to have "dep_bool" and "dep_mbool" for this, a long time ago. It 
got dropped in the Kconfig language rewrite, and I think it was a mistake.

So I think it would be nice to re-introduce it. As it is, we have a number 
of Kconfig language constructs that are just unnecessarily hard to 
understand, because we end up having to add a "= y" or similar.

The rule *used* to be: "dep_mbool" was a boolean that was valid even for 
modules, while "dep_bool" was a boolean that was valid only for straigth 
"y", and a module would turn it off.

Maybe not "bool" vs "mbool", but it might be nice to have

	bool FB_PS3
		depends strictly on FB

ie a "depends strictly" refuses to upgrade a bool dependency from "m" to 
"y", while a regular depends allows it.

Or something.. The "depends strictly on X" thing would really be just a 
mental shorthand for "depends on (X)=y" (it's actually longer to type, but 
I think it's a bit more intuitive, thus "mental shortcut").

		Linus