linux-kernel - Re: [PATCH] gpiolib: add gpio_request/free

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]

Message-Id: <200906091756.11839.david-b@pacbell.net>
Date:	Tue, 9 Jun 2009 17:56:11 -0700
From:	David Brownell <david-b@...bell.net>
To:	"H Hartley Sweeten" <hartleys@...ionengravers.com>
Cc:	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpiolib: add gpio_request/free_irq

On Tuesday 09 June 2009, H Hartley Sweeten wrote:
> On Friday, June 05, 2009 10:20 PM, David Brownell wrote:
> > On Friday 05 June 2009, H Hartley Sweeten wrote:
> > Add support functions to gpiolib to request/free gpio irqs.
> > 
> > I'm not keen on this.
> > 
> >  - At best it's a convenience layer ... for something that's
> >    not the least bit awkward to do otherwise.
> 
> 		... deletia ...
> 
> >  - Coupling it to gpiolib sort of defeats the point of saying
> >    that gpiolib is just an *implementation* of the interface.
> >    Where's the code to run for non-gpiolib platforms?
> > 
> 
> But if a driver is using the gpiolib interface calls wouldn't that
> prevent that driver from working on a platform that does not support
> gpiolib? File include/linux/gpio.h defines all the gpiolib calls to
> either return an error code or WARN_ON(1) when called.

There are three kinds of config to be concerned with:

 - Platform doesn't support the GPIO calls at all.  In those
   cases, drivers using <linux/gpio.h> get NOP stubs; you have
   this case covered.

 - Platforms supporting the calls but not using gpiolib.
   That's the case I pointed out -- you don't handle it.

 - Platforms supporting the calls with gpiolib.  This is the
   other case you handle.


> >  - Since it implicitly couples gpio_request() to a flavor of
> >    request_irq(), it precludes sharing those IRQs.
> > 
> 
> Can't the IRQ be shared by passing IRQF_SHARED as one of the flags?

Only one of them will be able to gpio_request(), so it
doesn't matter at all what you say to request_irq().


> > Basically, board setup can know that the GPIO is being used
> > as an IRQ, and do the request()/direction_input() before it
> > passes gpio_to_irq() to the driver. That's worked in every
> > case I've happened across so far...
> 
> I agree it works as-is right now.  I just thought this would be a
> convenient wrapper to handle a common setup step.  If it's overkill
> or not appropriate to add to gpiolib please disregard the patch.


--
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/