linux-kernel - Re: [PATCH v3] drivers/pinctrl: grab default handles from device core

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Message-ID: <CACRpkdYXmgOiuiW2Ccas375_3zfrqiOML5qWxaXP4Qzm6KEmWw@mail.gmail.com>
Date:	Mon, 21 Jan 2013 20:13:59 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Linus Walleij <linus.walleij@...ricsson.com>,
	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Anmar Oueja <anmar.oueja@...aro.org>,
	Felipe Balbi <balbi@...com>, Benoit Cousson <b-cousson@...com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Mitch Bradley <wmb@...mworks.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Rickard Andersson <rickard.andersson@...ricsson.com>
Subject: Re: [PATCH v3] drivers/pinctrl: grab default handles from device core

On Fri, Jan 18, 2013 at 9:13 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Fri, Jan 18, 2013 at 04:08:48PM +0100, Linus Walleij wrote:
>> - Abstain from using IS_ERR_OR_NULL() in the driver core,
>>   Russell recently sent a patch to remove it. Handle the
>>   NULL case explicitly even though it's a bogus case.
>
> Hmmmmmmmm... I assume you're talking about this:
>
>> +     p = create_pinctrl(dev);
>> +     if (p && !IS_ERR(p))
>> +             kref_init(&p->users);
>> +     return p;
>
> which is... interesting.  In mainline currently, the version I see there
> never returns NULL - it either returns an err pointer or a real pointer.

Actually it was this thing:

+ dpi->p = devm_pinctrl_get(dev);
+ if (!dpi->p) {
+    /* Shouldn't happen, but handle this anyway */
+    dev_warn(dev, "devm_pinctrl_get() returned NULL\n");
+    devm_kfree(dev, dpi);
+    dev->pins = NULL;
+    return 0;
+ }

I will delete both NULL checks and spin a v4.

> Next thing though is...
>
> create_pinctrl adds the struct pinctrl onto the global list, and then you
> intialize it here, which is an interesting sequence.  It's safe at the
> moment because everything here is operating under a mutex, but it's a
> little obscure.
>
> Is there a reason not to initialize p->users inside create_pinctrl() ?

Not really. I'll fix it...

Yours,
Linus Walleij
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