Message-ID: <27197467.RMEiFLZMHQ@d46>
Date:	Fri, 17 Oct 2014 09:49:24 +0200
From:	Thomas Renninger <trenn@...e.de>
To:	minyard@....org, martin.wilck@...fujitsu.com
Cc:	linux-kernel@...r.kernel.org,
	openipmi-developer@...ts.sourceforge.net
Subject: Re: [patch 1/3] ipmi: Setup ipmi_devintf automatically if ipmi_msghandler gets loaded

Hi,

On Tuesday, October 14, 2014 08:22:20 PM Corey Minyard wrote:
> On 10/14/2014 09:40 AM, trenn@...e.de wrote:
> > This removes the ipmi_devintf to be a module, but it will automatically
> > compiled in if ipmi_msghandler is set.
> > 
> > ipmi_msghandler module is renamed to ipmi_handler because of the name
> > clash with the ipmi_msghandler.o object file (see Makefile for details).
> > Alternatively ipmi_msghandler.c could be renamed to ipmi_handler.c, but
> > not polluting git history should be more of an advantage than module
> > renaming.
> > 
> > cleanup_ipmi_dev() and init_ipmi_devintf() implemented in ipmi_devintf.c
> > are are simply declared ipmi_msghandler.c without creating a separate
> > header file which looks more reasonable to me. Hope that is ok.
> 
> One minor style issue: the function definitions should really be in a .h
> file.
Ok.

> Renaming the module is also probably a bad idea.  If this was to go in,
> it would certainly need to keep the ipmi_msghandler.ko name to avoid
> complete breakage all over the place.
? What should break?
It should never be needed to load ipmi_msghandler manually.
Even if autoloading does not work, loading the low level
serving driver (e.g. ipmi_si) is enough. This one will request
ipmi_(msg)handler.ko automatically.
I excpect this is the same for all other ipmi HW serving drivers, right?

> In that vein, I am worried that this would just result in a lot of work
> for all the distros that have set up this already.
We also loaded the ipmi driver manually via the OpenIPMI init service
which simply tried to load ipmi drivers.
This results in boot load time, resource and code overhead.
As ipmi autoload seem to work fine for recent HW these days, the userspace
interface should load as well, otherwise the whole autoloading is more
or less useless.

> I'm trying to see the pros and cons of
> this, and I can't see that the pros outweigh the cons.  Do you have people
> that have issues with this?

Yes. In fact Fujitsu opened a bug for this. Unfortunately I cannot set it
public as it is against SLES12. If I find a way, I'll reference it in
the changelog:
https://bugzilla.novell.com/show_bug.cgi?id=893181
Subject:
ipmi_devintf is not available when IPMI device is detected

I already added Martin to CC: of the patch changelog, but quilt may
not have recogized it and not added him to CC?

Beside Fujitsu, I'd like to have this fixed as well.
We adjust BMC settings via after install script on our servers via
ipmitool. This does not work because of this bug.
One has to:
modprobe ipmi_devintf
This is overhead and makes the whole autoloading mechanism useless.
And even worse, ipmi_devintf seem to load on all machines whether they
have an ipmi controller or not.


> > In fact there already was a kind of autoloading mechanism (gets deleted
> > with this patch). I interpret this line that ipmi_devintf should get
> > autoloaded if ipmi_si gets loaded?:
> > -MODULE_ALIAS("platform:ipmi_si");
> > 
> > But:
> >   - It's wrong: There are other low lever drivers which can be used by
> >   
> >     ipmi_devintf
> >   
> >   - It does not work (anymore?)
> >   - There is no need to keep ipmi_devintf as a module (resource and load
> >   time
> >   
> >     overhead)
> 
> This change is certainly a good idea.  Whatever it was trying to do is
> wrong.

Thanks. I am convinced that the right way to go for is to integrate the 
ipmi_devintf into ipmi_msghandler.

I see 3 options how to do this:
  - rename ipmi_msghandler.ko to ipmi_handler.ko
    As this only is an interface provider for other modules getting
    loaded/requested automatically and never needs to be loaded manually
    (pls correct me if I am wrong), I would like to go for this option.

  - rename ipmi_msghandler.c to ipmi_handler.c
    -> git history lost. But should still be seen via:
    git log --follow?

  - Someone finds another way how to modify the Makefile to achieve above.

Thanks,

     Thomas
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