linux-kernel - Re: [PATCH 3/4] leds: add LM3533 LED driver

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Message-ID: <20120420164553.GA12376@localhost>
Date:	Fri, 20 Apr 2012 18:45:53 +0200
From:	Johan Hovold <jhovold@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Richard Purdie <rpurdie@...ys.net>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Florian Tobias Schandinat <FlorianSchandinat@....de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-fbdev@...r.kernel.org
Subject: Re: [PATCH 3/4] leds: add LM3533 LED driver

On Fri, Apr 20, 2012 at 04:10:15PM +0000, Arnd Bergmann wrote:
> On Friday 20 April 2012, Johan Hovold wrote:
> > Add sub-driver for the LEDs in National Semiconductor / TI LM3533
> > lighting power chips.
> > 
> > The chip provides 256 brightness levels, hardware accelerated blinking
> > as well as ambient-light-sensor and pwm input control.
> > 
> > Signed-off-by: Johan Hovold <jhovold@...il.com>
> 
> I notice that there is already driver for lm3530, which sounds related.
> Is there an opportunity to share code between these, or are they completely
> different devices?

Unfortunately not. They are really very different devices despite
similar naming and terminology.

> > +
> > +#define show_ctrlbank_attr(_name)					\
> > +static ssize_t show_##_name(struct device *dev,				\
> > +				struct device_attribute *attr,		\
> > +				char *buf)				\
> > +{									\
> > +	struct led_classdev *led_cdev = dev_get_drvdata(dev);		\
> > +	struct lm3533_led *led = to_lm3533_led(led_cdev);		\
> > +	u8 val;								\
> > +	int ret;							\
> > +									\
> > +	ret = lm3533_ctrlbank_get_##_name(&led->cb, &val);		\
> > +	if (ret)							\
> > +		return ret;						\
> > +									\
> > +	return scnprintf(buf, PAGE_SIZE, "%d\n", val);			\
> > +}
> 
> IMHO this macro adds more in terms of complexity than it saves in terms
> of lines of code, and it would be better to open-code the two instances.
> If you need more than two or three instances, I would recommend creating
> keying the number off of the attribute pointer, either by comparing the
> pointer or by adding a data structure derived from device_attribute and
> using container_of to get at the other data.

Agreed. I'll simply open-code them for now, and do the same with the
equivalent instances in the backlight driver.

Thanks,
Johan
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