linux-kernel - Re: [PATCH v4 1/2] hwmon: tmp513: Add max_channels variable to struct tmp51x

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Message-ID: <ZPiT606wpCDsNVPC@smile.fi.intel.com>
Date:   Wed, 6 Sep 2023 17:59:55 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Biju Das <biju.das.jz@...renesas.com>
Cc:     Eric Tremblay <etremblay@...tech-controls.com>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Biju Das <biju.das.au@...il.com>
Subject: Re: [PATCH v4 1/2] hwmon: tmp513: Add max_channels variable to
 struct tmp51x_data

On Wed, Sep 06, 2023 at 02:46:37PM +0000, Biju Das wrote:
> > On Tue, Sep 05, 2023 at 07:42:51PM +0100, Biju Das wrote:

...

> > > +#define TMP51X_TEMP_CONFIG_CONV_RATE	FIELD_PREP(GENMASK(9, 7), 0x7)
> > > +#define TMP51X_TEMP_CONFIG_RC		BIT(10)
> > > +#define TMP51X_TEMP_CHANNEL_MASK(n)	FIELD_PREP(GENMASK(14, 11), \
> > > +						   GENMASK((n) - 1, 0))
> > 
> > Why do you need FIELD_PREP() for the pure constants here? Why can you
> > simply define the constants in the proper place?
> 
> I think one can clearly understand the bit definitions and value from FIELD_PREP.

I think it is clear over engineering. In the first one the constant can't be
more than the field, in the second the defensive programming that is discouraged
in the kernel.

#define TMP51X_TEMP_CHANNEL_MASK(n)	(GENMASK((n) - 1, 0) << 11)

would suffice and much easier to understand.

...

> > > +#define TMP51X_TEMP_CONFIG_DEFAULT(n)	(TMP51X_TEMP_CONFIG_CONT | \
> > > +			TMP51X_TEMP_CHANNEL_MASK(n) | \
> > > +			TMP51X_TEMP_CONFIG_CONV_RATE | TMP51X_TEMP_CONFIG_RC)
> > 
> > This is better to read in a form of
> > 
> > #define TMP51X_TEMP_CONFIG_DEFAULT(n)					\
> > 	(TMP51X_TEMP_CHANNEL_MASK(n) | TMP51X_TEMP_CONFIG_CONT |	\
> > 	 TMP51X_TEMP_CONFIG_CONV_RATE | TMP51X_TEMP_CONFIG_RC)
> > 
> 
> I just used the indentation suggested by Guenter.

But wouldn't my proposal be sightly better to read?

-- 
With Best Regards,
Andy Shevchenko