linux-kernel - Re: [PATCH] VMware balloon: force compiling as a module

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Date:	Thu, 1 Jul 2010 15:43:47 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Dmitry Torokhov <dtor@...are.com>
Cc:	Bruno Prémont <bonbons@...ux-vserver.org>,
	Alexander Clouter <alex@...riz.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] VMware balloon: force compiling as a module

On Thu, 1 Jul 2010 15:31:50 -0700
Dmitry Torokhov <dtor@...are.com> wrote:

> On Thursday, July 01, 2010 03:18:35 pm Andrew Morton wrote:
> > On Tue, 29 Jun 2010 09:40:38 -0700
> > 
> > Dmitry Torokhov <dtor@...are.com> wrote:
> > > On Tuesday, June 29, 2010 09:28:59 am Bruno Pr__mont wrote:
> > > > On Tue, 29 June 2010 Alexander Clouter <alex@...riz.org.uk> wrote:
> > > > > Dmitry Torokhov <dtor@...are.com> wrote:
> > > > > > VMware Tools installer requires the upstream driver to be compiled
> > > > > > as a module in order to detect its presence and avoid installing
> > > > > > our own version on top of it. To avoid surprises with 2 versions
> > > > > > of the driver being installed and fighting with each other, let's
> > > > > > force the driver to be compiled as a module unless user selects
> > > > > > CONFIG_EMBEDDED.
> > > > > 
> > > > > *barf*
> > > > > 
> > > > > This surely is a problem in the installer and not the kernel?  Can
> > > > > you not nosey around in /sys/class/misc or where-ever your driver
> > > > > appears? If it does not, then I would probably suggest a patch to
> > > > > your balloon driver that dumps some details in there, including
> > > > > module version information.
> > > > > 
> > > > > Eugh.
> > > > 
> > > > In addition, the installer may check under /sys/module/ for it (as for
> > > > any/most code that can be built as a module), even for built-in code.
> > > > (if balloon driver does not show up there when built-in it would be
> > > > better to get it to show up there)
> > > 
> > > When driver is built-in the only thing exported in /sys/module/XXX are
> > > module parameters.
> > > 
> > > We also need to handle scenario when module is not loaded into the
> > > kernel.
> > 
> > - check for the /sys/module directory.
> 
> Empty.

But the presence of the empty /sys/module/vmware_balloon tells you that
the driver is loaded?

Confused.

> > 
> > - if that failed, modprobe the driver
> > 
> 
> Succeeds since the driver name changed (we renamed it to vmware_balloon
> before submitting into mainline to avoid confusion based on our experience
> with pvscsi; the existing one in the wild is called vmmemctl).
> 
> Now we have 2 drivers fighting. There is no backing device and so driver
> core will not save us by refusing to bind to already claimed device.

If vmware_balloon is present in /sys/modules or is loaded, don't load
vmmemctl.  And vice versa.

I dunno - it's silly for me to sit here proposing solutions.  it's
better that you do it!


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