linux-kernel - Re: [PATCHv2] qla2xxx: Correct compilation issues when CONFIG

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Message-Id: <1253029631.29947.156.camel@mulgrave.site>
Date:	Tue, 15 Sep 2009 10:47:11 -0500
From:	James Bottomley <James.Bottomley@...e.de>
To:	Greg KH <greg@...ah.com>
Cc:	Andrew Vasquez <andrew.vasquez@...gic.com>,
	Linux SCSI Mailing List <linux-scsi@...r.kernel.org>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	"linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Giridhar Malavali <giridhar.malavali@...gic.com>,
	Ravi Anand <ravi.anand@...gic.com>,
	Lalit Chandivade <lalit.chandivade@...gic.com>
Subject: Re: [PATCHv2] qla2xxx: Correct compilation issues when
 CONFIG_MOUDLES=n.

On Tue, 2009-09-15 at 08:33 -0700, Greg KH wrote:
> On Sat, Sep 12, 2009 at 09:30:07AM -0500, James Bottomley wrote:
> > On Fri, 2009-09-11 at 21:33 -0700, Greg KH wrote:
> > > On Fri, Sep 11, 2009 at 07:56:23PM -0700, Andrew Vasquez wrote:
> > > > On Fri, 11 Sep 2009, Greg KH wrote:
> > > > 
> > > > > On Fri, Sep 11, 2009 at 05:38:08PM -0700, Andrew Vasquez wrote:
> > > > > > Randy Dunlap noted:
> > > > > > 
> > > > > >   when CONFIG_MODULES=n:
> > > > > > 
> > > > > > 	drivers/scsi/qla2xxx/qla_os.c:2685: error: dereferencing pointer to incomplete type
> > > > > > 
> > > > > >   in
> > > > > > 
> > > > > > 	kobject_uevent_env(&(&vha->hw->pdev->driver->driver)->owner->mkobj.kobj,
> > > > > > 		KOBJ_CHANGE, envp);
> > > > > > 
> > > > > > Trigger kobject event on the 'struct device' hanging off the pci_dev.
> > > > > 
> > > > > Um, why?  What are you trying to do here?  kobject change should not be
> > > > > for a device, or a "normal" kobject.
> > > > > 
> > > > > What do you expect userspace to do with this?  Where have you documented
> > > > > it?
> > > > 
> > > > The purpose was described here:
> > > > 
> > > > 	http://article.gmane.org/gmane.linux.scsi/54155
> > > > 
> > > > Basically we'd like to instruct user-space to retrieve a blob of data
> > > > automatically.
> > > 
> > > Hm, like a firmware object perhaps?
> > > 
> > > > Original implementation used the kboject hanging off
> > > > the module which does not exist when CONFIG_MODULES=n.  It was
> > > > suggested that perhaps an alternative would be to use 'struct device'
> > > > kobj.  Any tips on how to trigger such a driver-specific event,
> > > > perhaps a dedicated kobject exported by the driver itself???
> > > 
> > > Why not use the firmware interface for it, that is what it is designed
> > > for, and you will not have to craft any new udev rules.
> > 
> > The data is going the wrong way to use the current firmware interface,
> > which is designed to load data from userspace into the kernel.  For this
> > interface, we want the data to go the other way (i.e. the kernel has a
> > blob of dump data it would like userspace to save if it can).
> 
> Ick.

It's a natural debugging event ... the user can simply program the
system to discard the dump.

> > I'd be amenable to updating the firmware interface to do this, but it
> > looks like adding a completely new codepath, which it's not clear even
> > belongs there.
> 
> Well, I don't think it deserves a kobject change event, as that means
> something a bit different to userspace today, right?

Well, the documentation (in include/linux/kobject.h) does say that
KOBJ_CHANGED is the dumping ground for events that don't match anything
else, which this one seems to qualify as.  What else do you suggest?

> Either way, I see no documentation being added to the Documentation/ABI/
> directory describing what is happening here, that needs to be added at
> the least.

OK, we can add that in the next go around.

Andrew, I actually dropped the patch (just this one, not the rest of the
qla2xxx patches) from the tree, so we can work on updating this as a
whole.

James


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