linux-kernel - Re: [PATCH v3] gpio: pcf857x: Add OF support

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Date:	Mon, 26 Aug 2013 15:41:43 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Sylwester Nawrocki <sylvester.nawrocki@...il.com>
Cc:	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v3] gpio: pcf857x: Add OF support

Hi Sylwester,

On Sunday 25 August 2013 10:16:40 Sylwester Nawrocki wrote:
> On 08/25/2013 02:26 AM, Laurent Pinchart wrote:
> > Add DT bindings for the pcf857x-compatible chips and parse the device
> > tree node in the driver.
> > 
> > Signed-off-by: Laurent Pinchart<laurent.pinchart+renesas@...asonboard.com>
> > ---
> > 
> >   .../devicetree/bindings/gpio/gpio-pcf857x.txt      | 71 ++++++++++++++++
> >   drivers/gpio/gpio-pcf857x.c                        | 57 +++++++++++++---
> >   2 files changed, 119 insertions(+), 9 deletions(-)
> >   create mode 100644
> >   Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt
> > 
> > Changes since v2
> > 
> > - Replace mention about interrupts software configuration in DT bindings
> >    documentation with an explanation of the hardware configuration.
> 
> [...]
> 
> > @@ -257,14 +280,29 @@ fail:
> >   static int pcf857x_probe(struct i2c_client *client,
> >   			 const struct i2c_device_id *id)
> >   {
> > -	struct pcf857x_platform_data	*pdata;
> > +	struct pcf857x_platform_data	*pdata = dev_get_platdata(&client-
> > >dev);
> > +	struct device_node		*np = client->dev.of_node;
> >   	struct pcf857x			*gpio;
> > +	unsigned int			n_latch = 0;
> > +	unsigned int			ngpio;
> >   	int				status;
> > 
> > -	pdata = dev_get_platdata(&client->dev);
> > -	if (!pdata) {
> > +#ifdef CONFIG_OF
> > +	if (np) {
> > +		const struct of_device_id *of_id;
> > +
> > +		of_id = of_match_device(pcf857x_of_table,&client->dev);
> > +		ngpio = (unsigned int)of_id->data;
> 
> It is potentially unsafe, since of_match_device() can return NULL.

But if np isn't NULL the probe function will only get called if there's a 
match in the OF table, so of_match_device() won't return NULL.

> > +	} else
> > +#endif
> > +		ngpio = id->driver_data;
> 
> CodingStyle: braces are missing for the second part of the if statement.
> 
> 
> How about something along the lines of:
> 
> 	const struct of_device_id *of_id;
> 
> 	of_id = of_match_device(of_match_ptr(pcf857x_of_table), &client->dev);
> 	if (of_id)
> 		ngpio = (unsigned int)of_id->data;
> 	else
> 		ngpio = id->driver_data;
> 
> to get rid of the #ifdef ?

Looks good to me, I'll post v4.

> But still DT has priority over platform data here.
> 
> > +
> > +	if (pdata)
> > +		n_latch = pdata->n_latch;
> > +	else if (IS_ENABLED(CONFIG_OF)&&  np)
> > +		of_property_read_u32(np, "pins-initial-state",&n_latch);
> 
> And here platform data has priority over DT.

We can't have both platform data and DT, but I'll change the order anyway.

> > +	else
> >   		dev_dbg(&client->dev, "no platform data\n");
> > -	}
> >   	/* Allocate, initialize, and register this gpio_chip. */
> >   	gpio = devm_kzalloc(&client->dev, sizeof(*gpio), GFP_KERNEL);

-- 
Regards,

Laurent Pinchart

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