Re: [PATCH v6 09/12] iio: dac: ad5686: add helpers to handle powerdown masks

[Andy Shevchenko]

On Tue, May 05, 2026 at 03:13:43PM +0100, Rodrigo Alencar wrote:
> On 26/05/05 04:17PM, Andy Shevchenko wrote:
> > On Tue, May 05, 2026 at 01:35:10PM +0100, Rodrigo Alencar via B4 Relay wrote:

...

> > > +static inline void ad5686_pd_field_set(const struct iio_chan_spec *chan,
> > > +				       unsigned int *pd, unsigned int val)
> > > +{
> > > +	unsigned int shift = ad5686_pd_mask_shift(chan);
> > > +
> > > +	*pd = (*pd & ~(AD5686_PD_MSK << shift)) | ((val & AD5686_PD_MSK) << shift);
> > 
> > Just noticed that semantically this is more like _field_modify().
> > Besides that I would consider adding a shifted mask variable or definition
> > 
> > 
> > 	*pd = (*pd & ~AD5686_PD_MSK) | ((val << shift) & AD5686_PD_MSK);
> 
> We cannot do this as the mask would depend on the shift too. AD5686_PD_MSK is
> being defined with no shift, so that any shift needs to be applied at runtime.

In my proposal I thought of

#define AD5686_PD_MSK(shift)	(GENMASK(...) << (shift))

> > > +}
> > > +
> > > +static inline unsigned int ad5686_pd_field_get(const struct iio_chan_spec *chan,
> > > +					       unsigned int pd)
> > > +{
> > > +	unsigned int shift = ad5686_pd_mask_shift(chan);
> > > +
> > > +	return (pd >> shift) & AD5686_PD_MSK;
> > 
> > 	return (pd & AD5686_PD_MSK) >> shift;
> > 
> > accordingly.
> 
> Same here...

But maybe it's over engineered, and your version is okay... Maybe we can even
switch to
field_get()/field_prep()/u32_replace_bits()/u32_encode_bits()/u32_get_bits()
from bitfield.h.

> > > +}

...

> > > -	if (readin)
> > > -		st->pwr_down_mask |= 0x3U << ad5686_pd_mask_shift(chan);
> > > -	else
> > > -		st->pwr_down_mask &= ~(0x3U << ad5686_pd_mask_shift(chan));
> > > +	ad5686_pd_field_set(chan, &st->pwr_down_mask,
> > > +			    readin ? AD5686_PD_MSK_PWR_DOWN : AD5686_PD_MSK_PWR_UP);
> > 
> > TBH, I would leave the if-else untouched, only branches to change.
> 
> What would be the difference compared to this:
> 
> 	if (readin)
> 		ad5686_pd_field_set(chan, &st->pwr_down_mask, AD5686_PD_MSK_PWR_DOWN);
> 	else
> 		ad5686_pd_field_set(chan, &st->pwr_down_mask, AD5686_PD_MSK_PWR_UP);

That's what I thought about...

-- 
With Best Regards,
Andy Shevchenko