linux-kernel - Re: [PATCH] w1-gpio: add external pull-up enable callback

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Message-ID: <20090506093445.GA31875@buzzloop.caiaq.de>
Date:	Wed, 6 May 2009 11:34:45 +0200
From:	Daniel Mack <daniel@...aq.de>
To:	Ville Syrjälä <syrjala@....fi>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] w1-gpio: add external pull-up enable callback

On Wed, May 06, 2009 at 12:33:07PM +0300, Ville Syrjälä wrote:
> On Tue, May 05, 2009 at 02:43:33PM +0200, Daniel Mack wrote:
> > On embedded devices, sleep mode conditions can be tricky to handle,
> > Especially when processors tend to pull-down the w1 bus during sleep.
> > Bus slaves (such as the ds2760) may interpret this as a reason for
> > power-down conditions and entirely switch off the device.
> > 
> > This patch adds a callback function pointer to let users switch on and
> > off the external pull-up resistor. This lets the outside world know
> > whether the processor is currently actively driving the bus or not.
> 
> Looks simple enough but I wonder if you could just do this from the
> platform code. I suppose the downside would be that you would enable the
> pullup even if w1-gpio is not loaded.

That's right. Hence I put it where I believe it belongs to.

Thanks,
Daniel
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