linux-kernel - Re: [PATCH 3/3][update] PM / sleep: Introduce command line argument for sleep state enumeration

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Message-ID: <3836835.YaZPGXsEQ2@vostro.rjw.lan>
Date:	Sat, 14 Jun 2014 00:16:26 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Pavel Machek <pavel@....cz>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3][update] PM / sleep: Introduce command line argument for sleep state enumeration

On Friday, June 13, 2014 11:46:12 PM Pavel Machek wrote:
> Hi!
> 
> > > > > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > > > > 
> > > > > > On some systems the platform doesn't support neither
> > > > > > PM_SUSPEND_MEM nor PM_SUSPEND_STANDBY, so PM_SUSPEND_FREEZE is the
> > > > > > only available system sleep state.  However, some user space frameworks
> > > > > > only use the "mem" and (sometimes) "standby" sleep state labels, so
> > > > > > the users of those systems need to modify user space in order to be
> > > > > > able to use system suspend at all and that is not always possible.
> > > > > 
> > > > > I'd say we should fix the frameworks, not add option to change kernel
> > > > > interfaces.
> > > > > 
> > > > > Because, as you mentioned, if we add this, we are probably going to
> > > > > get stuck with it forever :-(.
> > > > 
> > > > Unfortunately, fixing the frameworks is rather less than realistic in any
> > > > reasonable time frame, since  Android. :-)
> > > 
> > > Actually, you still have the sources from android, and this issue
> > > sounds almost simple enough for binary patch.
> > > 
> > > Android misuses /proc/sys/vm/drop_caches, too, IIRC. Are we going to
> > > change interface to match their expectations? They have binder and
> > > wakelocks. Are we going to apply those patches just because Android
> > > wants that?
> > 
> > That depends on which versions of Android you're talking about.  The
> > newest ones use the power management interfaces we have upstream.
> 
> Ok, good, so they can fix their code.
> 
> What problem are you solving? Do you have some weird hardware where
> suspend to memory is impossible? 
> 
> > > Android people usually patch their kernels, anyway, so why not add
> > > this one, too?
> > 
> > I'm not talking about Android kernels, but about Android user space.
> 
> I know. Android userspace usually runs on modified kernel, so you can
> simply add your patch. But I don't think its suitable for mainline.  
> 
> > And this is not only about Android, other distros also have user space that
> > uses "mem" only, because nobody has used anything else for a long time anyway.
> > For the users of those distros, if they don't want to modify user space,
> > having a kernel command line like this is actually helpful.
> 
> Yes, still its wrong place to fix it...

This isn't a fix.  It's a workaround.

> > So I'm really not sure what's the problem?  Do you think it's wrong to be
> > helpful to users or something?
> 
> It is not wrong to be helpful, but messed up interface is too big a
> price.

Why?  I will have to maintain it after all, right?

Rafael

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