linux-kernel - RE: [PATCH V2 1/2] pinctrl: Introduce PINCTRL_STATE

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Date:	Wed, 29 Feb 2012 09:41:44 -0800
From:	Stephen Warren <swarren@...dia.com>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Linus Walleij <linus.walleij@...ricsson.com>,
	"B29396@...escale.com" <B29396@...escale.com>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"dongas86@...il.com" <dongas86@...il.com>,
	"shawn.guo@...aro.org" <shawn.guo@...aro.org>,
	"thomas.abraham@...aro.org" <thomas.abraham@...aro.org>,
	"tony@...mide.com" <tony@...mide.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V2 1/2] pinctrl: Introduce PINCTRL_STATE_DEFAULT, define
 hogs as that state

Linus Walleij wrote at Wednesday, February 29, 2012 9:41 AM:
> Aha now I see the problem here...
> 
> On Tue, Feb 28, 2012 at 12:55 AM, Stephen Warren <swarren@...dia.com> wrote:
> 
> > This provides a single centralized name for the default state.
> (...)
> > -/* Hog a single map entry and add to the hoglist */
> > -static int pinctrl_hog_map(struct pinctrl_dev *pctldev,
> (...)
> > -static int pinctrl_hog_maps(struct pinctrl_dev *pctldev)
> (...)
> > -       pinctrl_hog_maps(pctldev);
> > +       pctldev->p = pinctrl_get(pctldev->dev, PINCTRL_STATE_DEFAULT);
> > +       if (!IS_ERR(pctldev->p))
> > +               pinctrl_enable(pctldev->p);
> 
> So what happens here is that my hogs will try to activate three different
> functions in the same struct pinctrl *p.
> 
> This fails the sanity check in pinmux.c:
> 
> 	/*
> 	 * If the function selector is already set, it needs to be identical,
> 	 * we support several groups with one function but not several
> 	 * functions with one or several groups in the same pinmux.
> 	 */
> 	if (p->func_selector != UINT_MAX &&
> 	    p->func_selector != func_selector) {
> 		dev_err(pctldev->dev,
> 			"dual function defines in the map for device %s\n",
> 		       devname);
> 		return -EINVAL;
> 	}
> 	p->func_selector = func_selector;

Oh right, I'd forgotten about that check at this stage in the patch
series.

Later in the series, this restriction is removed; each setting in a state
is completely independent, and could easily program a different function
onto each group, or the same function. At this stage in the series, a
struct pinctrl can't represent everything that a set of mapping table
entries can, but later struct pinctrl is fully capable.

I guess the solution here is to just make this patch introduce the
PINCTRL_STATE_DEFAULT define, but defer most usage of it until later
in the series when this restriction is removed.

Note that if you apply all my patches together, you should find that
U300 is unbroken, so you can at least test everything. Actually
committing that probably isn't a good idea since it'll break git bisect
for a little while though.

-- 
nvpublic

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