linux-kernel - Re: [RFC PATCH 0/3] If an IRQ is a GPIO, request and configure it

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 5 Aug 2011 22:40:27 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Stephen Warren <swarren@...dia.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...com>, Chris Ball <cjb@...top.org>,
	"ccross@...roid.com" <ccross@...roid.com>,
	"olof@...om.net" <olof@...om.net>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH 0/3] If an IRQ is a GPIO, request and configure it

On Fri, Aug 05, 2011 at 12:33:31PM -0700, Stephen Warren wrote:
> Russell King - ARM Linux wrote at Friday, August 05, 2011 1:15 PM:
> > On Fri, Aug 05, 2011 at 08:43:20AM -0700, Stephen Warren wrote:
> > > Russell King - ARM Linux wrote at Friday, August 05, 2011 3:40 AM:
> > > > On Thu, Aug 04, 2011 at 05:00:17PM -0600, Stephen Warren wrote:
> > > > > In http://www.spinics.net/lists/linux-tegra/msg01731.html, Mark Brown
> > > > > pointed out that it was a little silly forcing every board or driver
> > > > > to gpio_request() a GPIO that is later converted to an IRQ, and passed
> > > > > to request_irq. The first patch in this series instead makes the core
> > > > > IRQ code perform these calls when appropriate, to avoid duplicating it
> > > > > everywhere.
> > > >
> > > > Trying to go from IRQ to GPIO is not a good idea - most of the
> > > > IRQ <-> GPIO macros we have today are just plain broken.  Many of them
> > > > just add or subtract a constant, which means non-GPIO IRQs have an
> > > > apparant GPIO number too.  Couple this with the fact that all positive
> > > > GPIO numbers are valid, and this is a recipe for wrong GPIOs getting
> > > > used and GPIOs being requested for non-GPIO IRQs.
> > > >
> > > > I think this was also discussed in the past, and the conclusion was that
> > > > IRQs should be kept separate from GPIOs.  Maybe views have changed since
> > > > then...
> > > >
> > > > However, if we do want to do this, then it would be much better to provide
> > > > a new API for requesting GPIO IRQs, eg:
> > > >
> > > > gpio_request_irq()
> > > >
> > > > which would wrap around request_threaded_irq(), takes a GPIO number,
> > > > does the GPIO->IRQ conversion internally, and whatever GPIO setup is
> > > > required.  Something like this:
> > >
> > > With that approach, drivers need to explicitly know whether they're
> > > passed a GPIO or an IRQ, and do something different, or they need to
> > > choose to only accept a GPIO or IRQ.
> > 
> > You completely missed the biggest reason why your approach is broken.
> 
> No, I didn't.

Yes you did.

> I was discussing whether an alternative API for IRQ registration
> would work, and I was pointing out some problems with it.
> 
> That has nothing to do with whether my original proposal is workable.

And that proves that you missed the point.  I am suggesting an alternative
solution precisely because your original proposal is unworkable.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/