linux-kernel - Re: [PATCH/RFC] pci: dynids.use_driver

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Date:	Thu, 14 Aug 2008 15:12:14 -0700
From:	Greg KH <greg@...ah.com>
To:	Jean Delvare <khali@...ux-fr.org>
Cc:	Milton Miller <miltonm@....com>,
	Michael Ellerman <michael@...erman.id.au>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH/RFC] pci: dynids.use_driver_data considered harmful

On Wed, Aug 06, 2008 at 09:31:18AM +0200, Jean Delvare wrote:
> Hi Greg,
> 
> On Thu, 17 Jul 2008 00:07:59 -0700, Greg KH wrote:
> > On Wed, Jul 16, 2008 at 05:18:18AM -0500, Milton Miller wrote:
> > >
> > > Greg,
> > >
> > > Please respond to this email and explain why the patch
> > >
> > > pci: dynids.use_driver_data considered harmful
> > >
> > > http://www.ussg.iu.edu/hypermail/linux/kernel/0807.1/index.html#2188
> > >
> > > should not be applied.   I am not arguing the correctness of
> > > the removed code, rather its utility and benefit to the linux
> > > community.
> >
> > (...)  I'll try to get
> > to this by Monday, but my original point still stands, this was
> > implemented for a reason,
> 
> Not a good enough argument, sorry. There have been many cases in the
> past where code has been withdrawn after some times because we
> realized that we got it wrong in the first place.

Fair enough :)

> So, please explain what the current code is good for. Honestly, my
> initial reaction to Milton's proposal was "what an idiot, this flag is
> there for an obvious safety reason and we don't want to remove it" but
> after reading both his arguments and the code, I found that I have
> nothing to backup my claim. If you do, please let us know your
> technical reasons.

The technical reason was that this flag was needed to let some drivers
work properly with the new_id file, right?

If the flag goes away, they break from what I can tell.

> >                           saying that not enough drivers use it properly
> > does not make the need for it to go away.  It is required for them, so
> > perhaps the other 419 drivers also need to have the flag set.  That's
> > pretty trivial to do, right?
> 
> If you are suggesting to blindly set the flag to all PCI drivers (or
> even just all the ones which make use of the driver_data field -
> doesn't make a difference), this simply shows how useless this flag is.
> If you don't, then one would have to check the code of all drivers and
> add validation code for the driver_data value; but then this no longer
> falls into the "trivial" category.

It's pretty "trivial" to look to see if the field is set in the pci_id
structure, that should be all that is needed, right?

thanks,

greg k-h
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