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

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Message-ID: <20160125133731.72669115@ipc1.ka-ro>
Date:	Mon, 25 Jan 2016 13:37:31 +0100
From:	Lothar Waßmann <LW@...O-electronics.de>
To:	Mark Brown <broonie@...nel.org>
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

Hi,

On Fri, 22 Jan 2016 16:26:10 +0000 Mark Brown wrote:
> 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.
>
Any suggestions how to handle this case in a more sensible way?


Lothar Waßmann