linux-kernel - Re: [PATCH] Add TAINT_HARDWARE

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Date:	Mon, 21 Jun 2010 13:00:08 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Prarit Bhargava <prarit@...hat.com>, linux-kernel@...r.kernel.org,
	Randy Dunlap <randy.dunlap@...cle.com>,
	alan@...rguk.ukuu.org.uk
Subject: Re: [PATCH] Add TAINT_HARDWARE_UNSUPPORTED flag

On Mon, 21 Jun 2010 15:45:59 -0400
Don Zickus <dzickus@...hat.com> wrote:

> On Mon, Jun 21, 2010 at 12:21:45PM -0700, Andrew Morton wrote:
> > > @@ -243,6 +245,9 @@ void add_taint(unsigned flag)
> > >  	 */
> > >  	if (flag != TAINT_CRAP && flag != TAINT_WARN && __debug_locks_off())
> > >  		printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
> > > +	if (flag == TAINT_HARDWARE_UNSUPPORTED)
> > > +		printk(KERN_CRIT
> > > +		       "WARNING: This system's hardware is unsupported.\n");
> > >  
> > >  	set_bit(flag, &tainted_mask);
> > >  }
> > 
> > That's pretty user-hostile.  What are they to do - throw the entire
> > computer away because it has the wrong type of mouse?
> > 
> > How about
> > 
> > void add_hardware_unsupported_taint(const char *hardware)
> > {
> > 	printk(KERN_CRIT
> > 	       "Hardware device %s is unsupported by this kernel's vendor\n",
> > 		hardware);
> > 	add_taint(TAINT_HARDWARE_UNSUPPORTED);
> > }
> > 
> > and
> > 
> > /*
> >  * Don't call add_taint(TAINT_HARDWARE_UNSUPPORTED) directly - use
> >  * add_hardware_unsupported_taint()
> >  */
> > #define TAINT_HARDWARE_UNSUPPORTED	12
> 
> Internally here that is how we planned on using the flag.  We weren't sure
> if upstream would accept that piece or not, so we started with the flag
> for now to at least reserve the bit.
> 
> But I can see your point about the other printk being a little
> user-hostile if someone forgot to call the wrapper function.
> 
> I can respin with the wrapper function (Prarit is on vacation)

Not telling the user _which_ hardware is causing the problem is daft.

> or go with
> Alan's idea of just reserving the upper few bits.

um.  Given that the vendor needs to patch the individual drivers to
indicate ther unsupported status, why not just patch in the taint
changes as well?


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