Re: [PATCH/RFC] pci: dynids.use_driver_data considered harmful

From: Greg KH <greg@kroah.com>
To: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Jean Delvare <khali@linux-fr.org>,
	Milton Miller <miltonm@bga.com>,
	Michael Ellerman <michael@ellerman.id.au>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-pci@vger.kernel.org
Subject: Re: [PATCH/RFC] pci: dynids.use_driver_data considered harmful
Date: Fri, 15 Aug 2008 23:22:59 -0700	[thread overview]
Message-ID: <20080816062259.GB20541@kroah.com> (raw)
In-Reply-To: <200808151215.02499.jbarnes@virtuousgeek.org>

On Fri, Aug 15, 2008 at 12:15:01PM -0700, Jesse Barnes wrote:
> On Friday, August 15, 2008 11:55 am Jean Delvare wrote:
> > In fact we can do even better than that. We could accept from
> > user-space only driver_data values which at least one device ID entry in
> > the driver already uses. That should be fairly easy to implement, and
> > would offer a level of safety an order of magnitude above what we have
> > at the moment... And it works both ways: if 0 is not a valid data for
> > some driver, that would force the user to provide a non-zero (and
> > valid) data value. And it guarantees that the user can't ask for
> > something the driver doesn't expect, so drivers don't even need extra
> > checks. And no need for a use_driver_data flag either.
> 
> Meaning a driver audit of the usage?  Yeah that would be great.
> 
> > The only drawback is that it prevents the user from passing a "new"
> > data value even if it would be valid. But honestly, I don't expect that
> > case to happen frequently... if ever at all. So I'd say the benefits
> > totally outweight the drawback.
> >
> > If the interested people agree with the idea, I'll look into
> > implementing it.
> 
> Well the audit would show if user supplied "new" values are needed; otherwise 
> the approach sounds good to me.

That sounds reasonable, and should work properly.

No objection from me.

thanks,

greg k-h