linux-kernel - Re: [PATCH v4 4/4] iio: adc: mcp3911: add support for the whole MCP39xx family

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Message-ID: <20230809190257.67602e55@jic23-huawei>
Date:   Wed, 9 Aug 2023 19:02:57 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Marcus Folkesson <marcus.folkesson@...il.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Kent Gustavsson <kent@...oris.se>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Cosmin Tanislav <demonsingur@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        ChiYuan Huang <cy_huang@...htek.com>,
        Haibo Chen <haibo.chen@....com>,
        Ramona Bolboaca <ramona.bolboaca@...log.com>,
        Ibrahim Tilki <Ibrahim.Tilki@...log.com>,
        ChiaEn Wu <chiaen_wu@...htek.com>,
        William Breathitt Gray <william.gray@...aro.org>,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/4] iio: adc: mcp3911: add support for the whole
 MCP39xx family

On Wed, 9 Aug 2023 08:41:05 +0200
Marcus Folkesson <marcus.folkesson@...il.com> wrote:

> > ...
> >   
> > > +#define MCP3910_OFFCAL(x)		(MCP3910_REG_OFFCAL_CH0 + x * 6)  
> > 
> > Inconsistent macro implementation, i.e. you need to use (x).  
> 
> Sorry, I do not get you
> 
> 
> [...]
> 
> > > +static int mcp3910_get_osr(struct mcp3911 *adc, int *val)
> > > +{
> > > +	int ret, osr;  
> > 
> > Strictly speaking osr can't be negative, otherwise it's a UB below.
> > 
> > 	u32 osr = FIELD_GET(MCP3910_CONFIG0_OSR, *val);
> > 	int ret;
> > 
> > and why val is int?  
> 
> I will change val to u32 for *_get_osr(), *_set_osr() and *_set_scale().
> 
> [...]
> 
> > > +	if (device_property_read_bool(&adc->spi->dev, "microchip,data-ready-hiz"))  
> > 
> > This also becomes shorter.
> > 
> > One trick to make it even shorter:
> > 
> > 	if (device_property_present(dev, "microchip,data-ready-hiz"))  
> 
> Thank you, I wasn't aware of device_property_present().

I know the read_bool function is direct equivalent of this but where a property
is a flag, it feels more natural to me to check it with that one.
read_present() feels more appropriate for where you want to know a more
complex property is present.

Doesn't matter that much either way however so up to you.

> 
> [...]
> 
> >   
> > > +	dev_dbg(&spi->dev, "use device address %i\n", adc->dev_addr);  
> > 
> > Is it useful?  
> 
> Yes, I think so.
> 
> > 
> > -- 
> > With Best Regards,
> > Andy Shevchenko
> > 
> >   
> 
> Best regards,
> Marcus Folkesson