linux-kernel - Re: [PATCH v2 5/8] rtc: isl12022: implement RTC_VL

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Message-ID: <ZIiJWKBFojAcNCkA@smile.fi.intel.com>
Date:   Tue, 13 Jun 2023 18:20:56 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/8] rtc: isl12022: implement RTC_VL_READ ioctl

On Tue, Jun 13, 2023 at 03:00:07PM +0200, Rasmus Villemoes wrote:
> Hook up support for reading the values of the SR_LBAT85 and SR_LBAT75
> bits. Translate the former to "battery low", and the latter to
> "battery empty or not-present".

A couple of nit-picks below.

...

> +static int isl12022_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
> +{
> +	struct regmap *regmap = dev_get_drvdata(dev);
> +	u32 user = 0, val;

This assignment can be done in the actual case below.

> +	int ret;
> +
> +	switch (cmd) {
> +	case RTC_VL_READ:
> +		ret = regmap_read(regmap, ISL12022_REG_SR, &val);
> +		if (ret < 0)

I always feel uneasy with ' < 0' — Does positive error makes sense?
Is it even possible? OTOH if the entire driver uses this idiom...
oh well, let's make it consistent.

> +			return ret;

		user = 0;

The rationale to avoid potential mistakes in the future in case this function
will be expanded and user will be re-used.

> +		if (val & ISL12022_SR_LBAT85)
> +			user |= RTC_VL_BACKUP_LOW;
> +
> +		if (val & ISL12022_SR_LBAT75)
> +			user |= RTC_VL_BACKUP_EMPTY;
> +
> +		return put_user(user, (u32 __user *)arg);
> +
> +	default:
> +		return -ENOIOCTLCMD;
> +	}
> +}

-- 
With Best Regards,
Andy Shevchenko