linux-kernel - Re: [PATCH v4] gpio: Add support for Intel SoC PMIC (Crystal Cove)

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Message-ID: <20140527151453.GB2067@lahna.fi.intel.com>
Date:	Tue, 27 May 2014 18:14:53 +0300
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	Alexandre Courbot <gnurou@...il.com>,
	"Zhu, Lejun" <lejun.zhu@...ux.intel.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	jacob.jun.pan@...ux.intel.com, bin.yang@...el.com
Subject: Re: [PATCH v4] gpio: Add support for Intel SoC PMIC (Crystal Cove)

On Tue, May 27, 2014 at 03:04:09PM +0300, Grygorii Strashko wrote:
> Hi Mika,
> 
> On 05/27/2014 11:46 AM, Mika Westerberg wrote:
> > On Tue, May 27, 2014 at 12:24:56PM +0300, Grygorii Strashko wrote:
> >>>> +
> >>>> +       if (retval) {
> >>>> +               dev_warn(&pdev->dev, "request irq failed: %d\n", retval);
> >>>> +               goto out;
> >>>> +       }
> >>>> +
> >>>> +       retval = gpiochip_add(&cg->chip);
> >>>> +       if (retval) {
> >>>> +               dev_warn(&pdev->dev, "add gpio chip error: %d\n", retval);
> >>>> +               goto out_free_irq;
> >>>> +       }
> >>
> >> As to my mind, It'll be better to setup IRQ as last probing step and
> >> free it as the first step of driver removing.
> > 
> > When gpiochip_add() is called the chip is exported to outside world. At
> > that point anyone can start requesting GPIOs and setup GPIO based
> > interrupts. How does that work if you setup the IRQ after you call
> > gpiochip_add()?
> > 
> 
> It's difficult for me to imagine case when GPIO will be accessed
> until GPIO driver's probe is finished.

Once you call gpiochip_add() your driver gets registered to the GPIO
subsystem and advertised outside. It doesn't matter whether your probe
function is finished or not.

> Regarding remove()/suspend() routines, It's like an axiom for me:
> - always disable irq
> - always stop all works/threads created by driver
> - do everything else
> (It's proved by dozens hours of debugging).

That's true for remove and suspend, yes but I'm not talking about them.

> Anyway, above is just my opinion :)
> So, It's up to you, because it's your code :)

No it's not, it's Lejun's driver :)
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