linux-kernel - Re: [PATCH v6 1/3] hwmon: Maxim MAX197 support

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Message-ID: <20120414004602.GA5609@ericsson.com>
Date:	Fri, 13 Apr 2012 17:46:02 -0700
From:	Guenter Roeck <guenter.roeck@...csson.com>
To:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
CC:	"x86@...nel.org" <x86@...nel.org>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	Jean Delvare <khali@...ux-fr.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Linus Walleij <linus.walleij@...ricsson.com>
Subject: Re: [PATCH v6 1/3] hwmon: Maxim MAX197 support

On Thu, Apr 12, 2012 at 08:28:53PM -0400, Vivien Didelot wrote:
> Signed-off-by: Vivien Didelot <vivien.didelot@...oirfairelinux.com>
> ---
[ ... ]

> +
> +/**
> + * max197_show_input() - Show channel input
> + *
> + * Function called on read access on in{0,1,2,3,4,5,6,7}_input
> + */
> +static ssize_t max197_show_input(struct device *dev,
> +                                struct device_attribute *devattr,
> +                                char *buf)
> +{
> +       struct max197_chip *chip = dev_get_drvdata(dev);
> +       struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
> +       int channel = attr->index;
> +       u16 raw;
> +       s32 scaled;
> +       int ret;
> +
> +       if (mutex_lock_interruptible(&chip->lock))
> +               return -ERESTARTSYS;
> +
> +       ret = chip->pdata->convert(chip->ctrl_bytes[channel], &raw);
> +       if (ret) {
> +               dev_err(dev, "conversion failed\n");
> +               goto unlock;
> +       }

Hi Vivien,

thinking about this, you can simplify the API to

	ret = chip->pdata->convert(chip->ctrl_bytes[channel]);
	if (ret < 0) {
		dev_err(dev, "conversion failed\n");
		goto unlock;
	}
	scaled = ret;

This overloads the return value with both error code (< 0) and return value (unsigned, >= 0).
This would make the code a bit simpler and smaller.

Thanks,
Guenter
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