linux-kernel - Re: [PATCH 1/2] Fix /sys/device/.../power/state

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Date:	Wed, 20 Dec 2006 19:04:28 -0800
From:	David Brownell <david-b@...bell.net>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	linux-kernel@...r.kernel.org, gregkh@...e.de
Subject: Re: [PATCH 1/2] Fix /sys/device/.../power/state

On Wednesday 20 December 2006 5:29 pm, Matthew Garrett wrote:
> On Wed, Dec 20, 2006 at 01:18:06PM -0800, David Brownell wrote:
> > >  	/* disallow incomplete suspend sequences */
> > > -	if (dev->bus && (dev->bus->suspend_late || dev->bus->resume_early))
> > > +	if (dev->bus && dev->bus->pm_has_noirq_stage 
> > > +	    && dev->bus->pm_has_noirq_stage(dev))
> > >  		return error;
> > >  
> > 
> > I'm suspecting these two patches won't be merged,

Make that "strongly suspecting" given what Greg said ... he normally
gets the final say over drivers/core/* things, and you seem alone in
wanting to help those sysfs files extend their withered existence.

> > but this fragment has 
> > two bugs.  One is the whitespace bug already mentioned.
> 
> I'm a bit curious about the whitespace issue - CodingStyle doesn't seem 
> to discuss what to do with if statements that end up longer than 80 
> characters, which is (I think) what you're talking about?

It does say that indents must use only tabs, which that clearly doesn't.
I think you'll find that

	if (some_very_long_condition
			&& probably_not_quite_as_long
			&& or_too_long_for_one_line) {
		do_this;
		and_this;
	}

is widely accepted.  (The conditions get an extra indent so they don't
look like they're part of the block executing if the test is true.)

> 
> > The other is that
> > the original test must still be used if that bus primitve doesn't exist.
> 
> I dislike that.

Tough noogies, as they say.  In a tradeoff between correctness and your
personal taste (or even mine, sigh!), the normal tradeoff is in favor
of correctness.

> We're asking to suspend an individual device - whether  
> the bus supports devices that need to suspend with interrupts disabled 
> is irrelevent, it's the device that we care about. We should just make 
> it necessary for every bus to support this method until the interface is 
> removed.

But you _didn't_ do anything to "make it necessary".  Which means that
your patch *WILL* cause bugs whenever a driver uses those calls, and
courtesy of your patch userspace tries to suspend that device ... 

> > > +       bus->pm_has_noirq_stage()
> > > -When:  July 2007
> > > +When:  Once alternative functionality has been implemented
> > 
> > The "When" shouldn't change.
> 
> We shouldn't remove interfaces that userland uses until there's been a 
> replacement for long enough that userland can switch over.

Userland can stop using this **TODAY** and just "ifdown", so that
argument seems weak.  For all your examples, the userland interface
is already available.

- Dave

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