Re: [PATCH 19/62] Driver-Core: devtmpfs - remove EXPERIMENTAL andenable it by default

From: Linus Torvalds
Date: Wed Mar 03 2010 - 11:57:49 EST

On Tue, 2 Mar 2010, Eric W. Biederman wrote:

> Greg Kroah-Hartman <gregkh@xxxxxxx> writes:
> > From: Kay Sievers <kay.sievers@xxxxxxxx>
> >
> > All major distros enable devtmpfs on recent systems, so remove
> > the EXPERIMENTAL flag, and enable it by default to reflect how it
> > is used today.
> Default y?
> Default y is the wrong thing for DEVTMPFS_MOUNT. It changes the
> userspace semantics so I can't see how this is safe in the general
> case.
> I also looked and the most recent bleeding edge distro I have fedora
> core 12 doesn't even compile in devtmpfs so this extraordinary claim
> that all major distros are using devtmpfs is far from true today. It
> is certainly rare enough that changing there is not yet justification
> for changing the default.

Yeah, this justification is pure and utter sh*t.

We don't just randomly move it from EXPERIMENTAL to make it 'default y'.

In fact, as mentioned yesterday in an unrelated thread, we NEVER make
something 'default y' unless it is required to maintain _old_ semantics
(ie some config option that is required for previous behavior to be true),
or unless it cures cancer.

Guys, I'll say it one more time: developers always feel that _their_
particular code is so important that it needs to be 'default y', because
obviously their code must be used by everybody.

But that is pure and utter CRAP.

Something like the core input layer might be 'default y' because quite
frankly, for 99% of users, if you don't enable it, the machine is useless.
And the original keyboard driver used to be compiled in without question.
And people who really don't want the input layer really _are_ special.

But some random new feature that nobody actually uses, has no legacy
reasons? Nope. It's simply not 'default y' material.

So I'm not going to pull this crap. People need to learn that 'default y'
is just WRONG.

Greg, please shut down people like Kay that want to enable something by
default. We want a _minimal_ working config, not a maximal. If somebody
has a distro that needs this, they can enable it _then_. Not "let's try to
make people enable it whether they need it or not, because they _might_".

Because "might need it" is simply not good enough. A "must have" is the
only reason to do 'default y'.

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