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

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Message-Id: <201204201610.15758.arnd@arndb.de>
Date:	Fri, 20 Apr 2012 16:10:15 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	Johan Hovold <jhovold@...il.com>
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 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?

> +
> +#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.

	Arnd
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