Re: [PATCH v2 26/46] mfd: ti_am335x_tscadc: Use FIELD_PREP() when relevant in the header

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Jonathan,

jic23@kernel.org wrote on Sun, 5 Sep 2021 14:13:32 +0100:

> On Thu,  2 Sep 2021 23:51:24 +0200
> Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> 
> > Use the FIELD_PREP() macro when relevant. Sometimes reorder the lines to
> > be able to use the relevant bitmask.
> > 
> > Mind the s/%d/%ld/ change in a log due to the type change following the
> > use of FIELD_PREP() in the header.
> > 
> > Suggested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>  
> What you have here is fine, but I would take it a step further and push the
> FIELD_PREP() calls directly inline in the code.  There is little advantage
> beyond saving a few characters in
> 
> STEPENB(3)
> 
> rather than
> 
> FIELD_PREP(STEPENB_MASK, 3)
> 
> If you don't want to go that far this is still an improvement so
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> > ---
> >  drivers/iio/adc/ti_am335x_adc.c      |  2 +-
> >  include/linux/mfd/ti_am335x_tscadc.h | 31 ++++++++++++++--------------
> >  2 files changed, 17 insertions(+), 16 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
> > index e946903b0993..54c410b6ca07 100644
> > --- a/drivers/iio/adc/ti_am335x_adc.c
> > +++ b/drivers/iio/adc/ti_am335x_adc.c
> > @@ -126,7 +126,7 @@ static void tiadc_step_config(struct iio_dev *indio_dev)
> >  		chan = adc_dev->channel_line[i];
> >  
> >  		if (adc_dev->step_avg[i] > STEPCONFIG_AVG_16) {
> > -			dev_warn(dev, "chan %d step_avg truncating to %d\n",
> > +			dev_warn(dev, "chan %d step_avg truncating to %ld\n",
> >  				 chan, STEPCONFIG_AVG_16);
> >  			adc_dev->step_avg[i] = STEPCONFIG_AVG_16;
> >  		}
> > diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h
> > index 4de16fc3d74f..29095c0dc6d8 100644
> > --- a/include/linux/mfd/ti_am335x_tscadc.h
> > +++ b/include/linux/mfd/ti_am335x_tscadc.h
> > @@ -8,6 +8,7 @@
> >  #ifndef __LINUX_TI_AM335X_TSCADC_MFD_H
> >  #define __LINUX_TI_AM335X_TSCADC_MFD_H
> >  
> > +#include <linux/bitfield.h>
> >  #include <linux/mfd/core.h>
> >  
> >  #define REG_RAWIRQSTATUS	0x024
> > @@ -40,7 +41,7 @@
> >  
> >  /* Step Enable */
> >  #define STEPENB_MASK		GENMASK(16, 0)
> > -#define STEPENB(val)		((val) << 0)
> > +#define STEPENB(val)		FIELD_PREP(STEPENB_MASK, (val))  
> 
> My inclination with these is to drop the macro entirely and
> just use FIELD_PREP(STEPENB_MASK, xxx) inline directly.
> There is no loss of clarity in doing so and it gets you to a state
> where you only have one macro per field which is nice for checking
> purposes.

Actually I don't like too much leaking FIELD_PREP()s directly in the
code because (and this is really a personal feeling) I found them
rather less straightforward to understand than a good old BIT() for
example. Moreover, I've already hacked in a lot of different
places and moving these definitions in the code directly would
produce a big diff, overall hardening possible future git-blames.

However, I rather agree on the fact that there is no point in defining
a mask and then using that mask in another macro unless that mask is
reused somewhere else. So if it's fine for you, I'll provide a new
version with a reduced number of defines in this file. Would this work
for you?
 
> 
> >  #define ENB(val)		BIT(val)
> >  #define STPENB_STEPENB		STEPENB(GENMASK(16, 0))
> >  #define STPENB_STEPENB_TC	STEPENB(GENMASK(12, 0))
> > @@ -58,11 +59,11 @@
> >  
> >  /* Step Configuration */
> >  #define STEPCONFIG_MODE_MASK	GENMASK(1, 0)
> > -#define STEPCONFIG_MODE(val)	((val) << 0)
> > +#define STEPCONFIG_MODE(val)	FIELD_PREP(STEPCONFIG_MODE_MASK, (val))
> >  #define STEPCONFIG_MODE_SWCNT	STEPCONFIG_MODE(1)
> >  #define STEPCONFIG_MODE_HWSYNC	STEPCONFIG_MODE(2)
> >  #define STEPCONFIG_AVG_MASK	GENMASK(4, 2)
> > -#define STEPCONFIG_AVG(val)	((val) << 2)
> > +#define STEPCONFIG_AVG(val)	FIELD_PREP(STEPCONFIG_AVG_MASK, (val))
> >  #define STEPCONFIG_AVG_16	STEPCONFIG_AVG(4)
> >  #define STEPCONFIG_XPP		BIT(5)
> >  #define STEPCONFIG_XNN		BIT(6)
> > @@ -70,43 +71,43 @@
> >  #define STEPCONFIG_YNN		BIT(8)
> >  #define STEPCONFIG_XNP		BIT(9)
> >  #define STEPCONFIG_YPN		BIT(10)
> > -#define STEPCONFIG_RFP(val)	((val) << 12)
> >  #define STEPCONFIG_RFP_VREFP	GENMASK(13, 12)
> > +#define STEPCONFIG_RFP(val)	FIELD_PREP(STEPCONFIG_RFP_VREFP, (val))
> >  #define STEPCONFIG_INM_MASK	GENMASK(18, 15)
> > -#define STEPCONFIG_INM(val)	((val) << 15)
> > +#define STEPCONFIG_INM(val)	FIELD_PREP(STEPCONFIG_INM_MASK, (val))
> >  #define STEPCONFIG_INM_ADCREFM	STEPCONFIG_INM(8)
> >  #define STEPCONFIG_INP_MASK	GENMASK(22, 19)
> > -#define STEPCONFIG_INP(val)	((val) << 19)
> > +#define STEPCONFIG_INP(val)	FIELD_PREP(STEPCONFIG_INP_MASK, (val))
> >  #define STEPCONFIG_INP_AN4	STEPCONFIG_INP(4)
> >  #define STEPCONFIG_INP_ADCREFM	STEPCONFIG_INP(8)
> >  #define STEPCONFIG_FIFO1	BIT(26)
> > -#define STEPCONFIG_RFM(val)	((val) << 23)
> >  #define STEPCONFIG_RFM_VREFN	GENMASK(24, 23)
> > +#define STEPCONFIG_RFM(val)	FIELD_PREP(STEPCONFIG_RFM_VREFN, (val))
> >  
> >  /* Delay register */
> >  #define STEPDELAY_OPEN_MASK	GENMASK(17, 0)
> > -#define STEPDELAY_OPEN(val)	((val) << 0)
> > +#define STEPDELAY_OPEN(val)	FIELD_PREP(STEPDELAY_OPEN_MASK, (val))
> >  #define STEPCONFIG_OPENDLY	STEPDELAY_OPEN(0x098)
> >  #define STEPDELAY_SAMPLE_MASK	GENMASK(31, 24)
> > -#define STEPDELAY_SAMPLE(val)	((val) << 24)
> > +#define STEPDELAY_SAMPLE(val)	FIELD_PREP(STEPDELAY_SAMPLE_MASK, (val))
> >  #define STEPCONFIG_SAMPLEDLY	STEPDELAY_SAMPLE(0)
> >  
> >  /* Charge Config */
> >  #define STEPCHARGE_RFP_MASK	GENMASK(14, 12)
> > -#define STEPCHARGE_RFP(val)	((val) << 12)
> > +#define STEPCHARGE_RFP(val)	FIELD_PREP(STEPCHARGE_RFP_MASK, (val))
> >  #define STEPCHARGE_RFP_XPUL	STEPCHARGE_RFP(1)
> >  #define STEPCHARGE_INM_MASK	GENMASK(18, 15)
> > -#define STEPCHARGE_INM(val)	((val) << 15)
> > +#define STEPCHARGE_INM(val)	FIELD_PREP(STEPCHARGE_INM_MASK, (val))
> >  #define STEPCHARGE_INM_AN1	STEPCHARGE_INM(1)
> >  #define STEPCHARGE_INP_MASK	GENMASK(22, 19)
> > -#define STEPCHARGE_INP(val)	((val) << 19)
> > +#define STEPCHARGE_INP(val)	FIELD_PREP(STEPCHARGE_INP_MASK, (val))
> >  #define STEPCHARGE_RFM_MASK	GENMASK(24, 23)
> > -#define STEPCHARGE_RFM(val)	((val) << 23)
> > +#define STEPCHARGE_RFM(val)	FIELD_PREP(STEPCHARGE_RFM_MASK, (val))
> >  #define STEPCHARGE_RFM_XNUR	STEPCHARGE_RFM(1)
> >  
> >  /* Charge delay */
> >  #define CHARGEDLY_OPEN_MASK	GENMASK(17, 0)
> > -#define CHARGEDLY_OPEN(val)	((val) << 0)
> > +#define CHARGEDLY_OPEN(val)	FIELD_PREP(CHARGEDLY_OPEN_MASK, (val))
> >  #define CHARGEDLY_OPENDLY	CHARGEDLY_OPEN(0x400)
> >  
> >  /* Control register */
> > @@ -115,7 +116,7 @@
> >  #define CNTRLREG_STEPCONFIGWRT	BIT(2)
> >  #define CNTRLREG_POWERDOWN	BIT(4)
> >  #define CNTRLREG_AFE_CTRL_MASK	GENMASK(6, 5)
> > -#define CNTRLREG_AFE_CTRL(val)	((val) << 5)
> > +#define CNTRLREG_AFE_CTRL(val)	FIELD_PREP(CNTRLREG_AFE_CTRL_MASK, (val))
> >  #define CNTRLREG_4WIRE		CNTRLREG_AFE_CTRL(1)
> >  #define CNTRLREG_5WIRE		CNTRLREG_AFE_CTRL(2)
> >  #define CNTRLREG_8WIRE		CNTRLREG_AFE_CTRL(3)  
> 

Thanks,
Miquèl