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

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Message-ID: <20230613090020b5405b61@mail.local>
Date:   Tue, 13 Jun 2023 11:00:20 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        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 5/8] rtc: isl12022: implement RTC_VL_READ and RTC_VL_CLR
 ioctls

On 13/06/2023 09:53:03+0200, Rasmus Villemoes wrote:
> On 12/06/2023 18.10, Alexandre Belloni wrote:
> > On 12/06/2023 18:48:49+0300, Andy Shevchenko wrote:
> >> On Mon, Jun 12, 2023 at 01:30:55PM +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".
> >>
> >> ...
> >>
> >>> +static int isl12022_read_sr(struct regmap *regmap)
> >>> +{
> >>> +	int ret;
> >>> +	u32 val;
> >>> +
> >>> +	ret = regmap_read(regmap, ISL12022_REG_SR, &val);
> >>> +	if (ret < 0)
> >>> +		return ret;
> >>> +	return val;
> >>
> >> Wondering if the bit 31 is in use with this register (note, I haven't checked
> >> the register width nor datasheet).
> >>
> > 
> > register width is in the driver:
> > 
> > static const struct regmap_config regmap_config = {
> > 	.reg_bits = 8,
> > 	.val_bits = 8,
> > 	.use_single_write = true,
> > };
> 
> Yeah.
> 
> But I only factored that out because I wanted to read the SR also in the
> isl12022_set_trip_levels() to emit the warning at boot time, but when
> that goes away, there's no longer any reason to not just fold this back
> into the ioctl() handler.

That would be to clear a not self clearable battery low (but not empty)
flag or a backup voltage switch flag.

> 
> Rasmus
> 

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com