From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Nigel Cunningham <nigel@suspend2.net>
Subject: Re: Which is simpler? (Was Re: [Suspend2-devel] Re: [ 00/10] [Suspend2] Modules support.)
Date: Tue, 7 Feb 2006 00:51:40 +0100
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Cc: suspend2-devel@lists.suspend2.net, Lee Revell <rlrevell@joe-job.com>,
       linux-kernel@vger.kernel.org, Pavel Machek <pavel@ucw.cz>
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Hi,

On Monday 06 February 2006 21:25, Nigel Cunningham wrote:
> On Tuesday 07 February 2006 04:48, Lee Revell wrote:
> > On Mon, 2006-02-06 at 15:43 +1000, Nigel Cunningham wrote:
> > > Hi.
> > >
> > > On Monday 06 February 2006 14:34, Lee Revell wrote:
> > > > On Mon, 2006-02-06 at 14:02 +1000, Nigel Cunningham wrote:
> > > > > (they now have to download extra
> > > > > libraries to use the splashscreen, which were not required with
> > > > > the bootsplash patch, and need to check whether an update to the
> > > > > userui code
> > > > > is required when updating the kernel)
> > > >
> > > > You could have avoided this problem by keeping the
> > > > userspace<->kernel interface stable.
> > >
> > > True, but sometimes you need to make changes that do modify the
> > > interface. If the interface involves more functionality, this will
> > > happen more frequently.
> >
> > Well, all I can say is, it should have been obvious that putting a
> > themeable UI in the kernel would not fly.
> 
> Agreed, but I think we have some confusion here.
> 
> I was talking about interactions between kernel space and userspace after 
> we started using the userspace interface. In particular, I was thinking of 
> the fact that the netlink message number kept changing due to changes in 
> the vanilla kernel. In the end, we just made it a command line option to 
> the userui.
> 
> My point for this conversation was different, though. If uswsusp ever does 
> fly, there are going to be flag days where users are going to have to 
> download new userspace code, perhaps new versions of libraries or new 
> libraries, run the compilation and reconfigure their initrds/ram-fses, all 
> just because they upgraded their kernel and want to continue to suspend to 
> disk. That is extra complexity introduced by using a userspace 'brain' 
> instead of having it in kernelspace.

This point is valid, but I don't think the users will _have_ _to_ switch to the
userland suspend.  AFAICT we are going to keep the kernel-based code
as long as necessary.

We are just going to implement features in the user space that need not be
implemented in the kernel.  Of course they can be implemented in the
kernel, and you have shown that clearly, but since they need not be there,
we should at least try to implement them in the user space and see how this
works.

Frankly, I have no strong opinion on whether they _should_ be implemented
in the user space or in the kernel, but I think we won't know that until
we actually _try_.

That said, I like the idea and I'm going to work on it.  I'll also appreciate
any help very much.

Greetings,
Rafael
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