linux-kernel - Re: [patch/rfc 2/4] pcf857x I2C GPIO expander driver

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Date:	Thu, 6 Dec 2007 20:02:17 -0800
From:	David Brownell <david-b@...bell.net>
To:	Jean Delvare <khali@...ux-fr.org>
Cc:	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Felipe Balbi <felipebalbi@...rs.sourceforge.net>,
	Bill Gatliff <bgat@...lgatliff.com>,
	Haavard Skinnemoen <hskinnemoen@...el.com>,
	Andrew Victor <andrew@...people.com>,
	Tony Lindgren <tony@...mide.com>,
	"eric miao" <eric.y.miao@...il.com>,
	Kevin Hilman <khilman@...sta.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Ben Dooks <ben@...nity.fluff.org>
Subject: Re: [patch/rfc 2/4] pcf857x I2C GPIO expander driver

On Thursday 06 December 2007, Jean Delvare wrote:

> 	Also, I don't quite see what
> is supposed to make compatibility with the legacy drivers easier, nor
> how, not why it matters in the first place.

There's a clear either/or disjunction.  No fuzzy/confusing middle ground.


> > +static int pcf857x_get8(struct gpio_chip *chip, unsigned offset)
> > +{
> > +	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
> > +	s32		value;
> > +
> > +	value = i2c_smbus_read_byte(gpio->client);
> > +	return (value < 0) ? 0 : (value & (1 << offset));
> 
> This is no longer a boolean value, is that OK? I guess that it doesn't
> matter but maybe it should be documented (what GPIO drivers are allowed
> to return in these callback functions.)

Already documented -- as zero/nonzero, the original boolean model for C.
Anything else would be at least tristate, not boolean.  :)


> > +	/* Let platform code set up the GPIOs and their users.
> > +	 * Now is the first time anyone can use them.
> > +	 */
> > +	if (pdata->setup) {
> > +		status = pdata->setup(client,
> > +				gpio->chip.base, gpio->chip.ngpio,
> > +				pdata->context);
> > +		if (status < 0)
> > +			dev_err(&client->dev, "%s --> %d\n",
> > +					"setup", status);
> 
> Shouldn't this be degraded to dev_warn? The probe still succeeds. Or
> keep dev_err but make the probe fail (in which case you'll probably
> want to swap this block of code with the dev_info above.)

Good point.


> The rest looks fine to me.

Thanks for the comments.  I'll send this in with the next batch
of gpiolib patches.

- Dave

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