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Date: Thu, 3 Jul 2008 01:06:45 +0200 From: "Rafael J. Wysocki" <rjw@...k.pl> To: Greg KH <greg@...ah.com> Cc: Andi Kleen <andi@...stfloor.org>, Nathan Lynch <ntl@...ox.com>, Andrew Morton <akpm@...ux-foundation.org>, Paul Mackerras <paulus@...ba.org>, torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org, Benjamin Herrenschmidt <benh@...nel.crashing.org> Subject: Re: Removing sysdevs? (was: Re: Is sysfs the right place to get cache and CPU topology info?) On Thursday, 3 of July 2008, Greg KH wrote: > On Thu, Jul 03, 2008 at 12:08:45AM +0200, Rafael J. Wysocki wrote: > > On Wednesday, 2 of July 2008, Greg KH wrote: > > > On Wed, Jul 02, 2008 at 11:41:44PM +0200, Rafael J. Wysocki wrote: > > > > On Wednesday, 2 of July 2008, Greg KH wrote: > > > > > On Wed, Jul 02, 2008 at 05:14:02PM +0200, Andi Kleen wrote: > > > > > > Nathan Lynch wrote: > > > > > > > Andi Kleen wrote: > > > > > > >> Andrew Morton <akpm@...ux-foundation.org> writes: > > > > > > >>> sysfs is part of the kernel ABI. We should design our interfaces there > > > > > > >>> as carefully as we design any others. > > > > > > >> The basic problem is that sysfs exports an internal kernel object model > > > > > > >> and these tend to change. To really make it stable would require > > > > > > >> splitting it into internal and presented interface. > > > > > > > > > > > > > > True, but... /sys/devices/system/cpu has been there since around 2.6.5 > > > > > > > iirc. A google code search for that path shows plenty of programs > > > > > > > (including hal) that hard-code it. Exposed object model or not, > > > > > > > changing that path would break lots of software. > > > > > > > > > > > > Yes it would. > > > > > > > > > > > > But Greg is making noises of getting rid of sysdevs and it wouldn't > > > > > > surprise me if that ended up being user visible since most object > > > > > > model changes end up being visible. > > > > > > > > > > I hope to make sysdevs go away in such a manner that the sysfs tree does > > > > > not change at all. That's my goal, but we still have a long ways to go > > > > > before we can even consider attempting to do this, so don't worry about > > > > > putting things in this location if you feel it is the best fit. > > > > > > > > Speaking of which, I'm very interested in the removing of sysdevs, since they > > > > don't fit into the new suspend/hibernation framework I'm working on. Can you > > > > please tell me what the plan is? > > > > > > The plan is: > > > - remaining driver core cleanups to allow for multiple drivers > > > to be bound to individual devices > > > - add multiple binding support to the core > > > - migrate existing sysdevs to struct device, now that multiple > > > binding is allowed > > > > Once they've been migrated to struct device, will they reside on specific > > 'system' bus, or will they be platform devices? > > I haven't really thought it through more than the above yet, so I don't > know :) This is quite important, though, because the device objects that sysdevs will be replaced with should provide suspend/hibernation callbacks to be run with interrupts disabled, while for some of them it may also be convenient to provide "normal" suspend/hibernation callbacks to be run with interrupts enabled. For this reason their bus type will have to be quite similar to the platform bus type. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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