linux-kernel - Re: [PATCH 1/2] regulator: ltc3589: make IRQ optional

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Date:	Fri, 22 Jan 2016 16:26:10 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Lothar Waßmann <LW@...O-electronics.de>
Cc:	Benoît Cousson <bcousson@...libre.com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Russell King <linux@....linux.org.uk>,
	Tony Lindgren <tony@...mide.com>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org
Subject: Re: [PATCH 1/2] regulator: ltc3589: make IRQ optional

On Fri, Jan 22, 2016 at 06:41:45AM +0100, Lothar Waßmann wrote:
> > On Thu, Jan 21, 2016 at 12:33:11PM +0100, Lothar Waßmann wrote:

> > Your commit message (quoted above) claims that without this patch if no
> > interrupt is supplied then the unsupplied interrupt will somehow be left
> > screaming and make the system unusable.  This doesn't make sense, if
> > there is no interrupt there is nothing to scream.

> "Otherwise" meant the case where the IRQ is specified in DT as is
> currently required to get the driver loaded at all.

> > So, contrary to what you've been saying, the interrupt is actually
> > connected (and worse, connected to a NMI) but apparently not described
> > in DT.  Why is it sensible to make the driver poll (which will affect
> > all systems using this device, even those that don't care) and not just
> > describe the interrupt in DT so it can be handled promptly in the normal
> > fashion?  Presumably this will run into serious problems if the
> > interrupt actually fires at runtime since the NMI will scream, it's not
> > clear to me how the poll will manage to run successfully in that case.

> Currently the driver won't even load without an IRQ specified in DT.
> My patch makes it possible to use the driver without requiring an IRQ!

You're not just making the interrupt optional, you are also implementing
polling support.  That's really unusual and there's no clear reason for
it, your changelog seems to claim that it is needed to make the system
work but that seems at best very surprising and would need a more
detailed changelog.

You at least need to provide an understandable changelog, though it
seems it is more likely that there is a more sensible way of dealing
with this.

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