linux-kernel - Re: [GPIO]implement sleeping GPIO chip removal

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Date:	Wed, 10 Nov 2010 14:45:16 -0800
From:	Greg KH <gregkh@...e.de>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Maciej Szmigiero <mhej@...pl>, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org,
	Anton Vorontsov <avorontsov@...mvista.com>,
	Uwe Kleine-K?nig <u.kleine-koenig@...gutronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Jonathan Cameron <jic23@....ac.uk>,
	Ben Nizette <bn@...sdigital.com>
Subject: Re: [GPIO]implement sleeping GPIO chip removal

On Wed, Nov 10, 2010 at 02:15:40PM -0700, Grant Likely wrote:
> On Wed, Nov 10, 2010 at 10:07:05PM +0100, Thomas Gleixner wrote:
> > Can you please use a mail client which does proper line breaks at 78 ?
> > 
> > On Wed, 10 Nov 2010, Maciej Szmigiero wrote:
> > > You misunderstood me.
> > 
> > No, I didnt.
> > 
> > > By "looping in hope that somebody will finally release the chip" I
> > > meant the only real way to handle a GPIO chip unplugging in the
> > > current kernel.  Which is way worse that preventing new requests,
> > > then waiting for existing one to be released.  And this is exactly
> > > what my patch does.
> > 
> > That still does not make it a good solution.
> > 
> > > I understand that it could be simplified by removing redundant code
> > > (as Grant Likely had suggested before), and moving it to completion
> > > interface instead of manipulating a task structure directly, but
> > > this doesn't mean that the whole GPIO code has to be rewritten just
> > > to add one functionality.
> > 
> > It's not about rewriting, it's about fixing the problem in the right
> > way and not just hacking around it.
> > 
> > If we see a shortcoming like this, we fix it and do not magically work
> > around it.
> 
> +1
> 
> Thomas is right.  kobject reference counting is the correct solution.
> Nack on this approach.

Only use a kobject if you want to be in the sysfs hierarchy (which I
don't think you want to do here.)  If you want proper reference
counting, use a 'struct kref' instead.

thanks,

greg k-h
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