linux-kernel - Re: [PATCH v7 2/3] gpio: mmio: add DT support for memory-mapped GPIOs

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Date:	Fri, 06 May 2016 14:22:23 +0200
From:	Christian Lamparter <chunkeey@...glemail.com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	devicetree <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
	Álvaro Fernández Rojas <noltari@...il.com>,
	Kumar Gala <galak@...eaurora.org>,
	Alexander Shiyan <shc_work@...l.ru>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v7 2/3] gpio: mmio: add DT support for memory-mapped GPIOs

On Friday, May 06, 2016 02:44:14 PM Andy Shevchenko wrote:
> > +       /* If ngpio property is not specified, of_property_read_u32
> > +        * will return -EINVAL. In this case the number of GPIOs is
> > +        * automatically determined by the register width. Any
> > +        * other error of of_property_read_u32 is due bad data and
> > +        * needs to be dealt with.
> 
> Couple style issues:
> /*
>  * First sentence starts here. func() are going with parens.
>  */
Ack, I'm used to drivers/net. I have to remove the ngpio in a future
version, so the comment is removed as well.

> > +
> > +static struct bgpio_pdata *bgpio_parse_dt(struct platform_device *pdev,
> > +                                         unsigned long *flags)
> > +{
> > +       const int (*parse_dt)(struct platform_device *,
> > +                             struct bgpio_pdata *, unsigned long *);
> > +       const struct device_node *node = pdev->dev.of_node;
> > +       const struct of_device_id *of_id;
> > +       struct bgpio_pdata *pdata;
> > +       int err = -ENODEV;
> 
> (1)
> 
> > +
> > +       of_id = of_match_node(bgpio_of_match, node);
> > +       if (!of_id)
> > +               return NULL;
> 
> (2)
> 
> Why so?

This is because of existing arch code in /arch/arm/mach-clps711x/board-p720t.c.
You remember there's a driver with a device-tree binding "cirrus,clps711x-gpio"
for it. But the current kernel arch code still registers a platform_device and
it doesn't look like it has any device tree support. So this is necessary for
those partially converted archs to co-exist with the driver. I'll update the
-ENODEV to -EINVAL.

> > +
> > +       pdata = devm_kzalloc(&pdev->dev, sizeof(struct bgpio_pdata),
> > +                            GFP_KERNEL);
> > +       if (!pdata)
> > +               return ERR_PTR(-ENOMEM);
> > +
> > +       parse_dt = (const void *)of_id->data;
> > +       if (parse_dt)
> > +               err = parse_dt(pdev, pdata, flags);
> > +       if (err)
> > +               return ERR_PTR(err);
> > +
> > +       return pdata;
> > +}
> > +#else
> > +static struct bgpio_pdata *bgpio_parse_dt(struct platform_device *pdev,
> > +                                         unsigned long *flags)
> > +{
> > +       return NULL;
> > +}
> > +#endif /* CONFIG_OF */