Re: [PATCH v3] iio: pressure: dps310: add triggered buffer support

[Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>]

On Sun, 19 Jul 2026 11:47:48 +0300
Andy Shevchenko <andriy.shevchenko@intel.com> wrote:

> On Sun, Jul 19, 2026 at 02:51:58AM +0300, Rupesh Majhi wrote:
> > Add triggered buffer support so pressure and temperature can be captured
> > into a buffer instead of only through one-shot sysfs reads.
> > 
> > Pressure is a processed value in kPa computed from a non-linear
> > calibration polynomial. To keep full resolution in the buffer without
> > disagreeing with the sysfs unit, add raw and scale attributes for
> > pressure (raw in Pa, scale 1/1000 to kPa), following bme680; the existing
> > processed attribute is kept for ABI compatibility. Temperature is already
> > a full-resolution value in its base unit (millidegrees Celsius) and stays
> > a processed channel.
> > 
> > Pressure compensation depends on a temperature reading, so both channels
> > are always captured together. The device already runs in continuous
> > background mode, so no buffer setup ops are needed. Sysfs reads and
> > reconfiguration return -EBUSY while the buffer is enabled, as they share
> > the capture path's raw values and configuration.  
> 
> Do not reply to the same thread with a new version.
> Do not reply within less than 24h.
> 
> The change needs more work, See my comments below.
> 
> ...
> 
> > +	/* Buffer to hold a scan; timestamp is naturally aligned */
> > +	struct {
> > +		s32 chan[2];
> > +		aligned_s64 timestamp;
> > +	} scan __aligned(8);  
> 
> We have a macro for this (alignment). Or even for the entire struct.

If (and I haven't checked) that is the required alignment it doesn't
need any marking at all.  The C spec requires a structure to be aligned
to the alignment of it's largest member.  Here alignment is forced to 8
by the aligned_s64.

> 
> ...
> 
> > +static const unsigned long dps310_scan_masks[] = { GENMASK(1, 0), 0 };  
> 
> Jonathan usually asks to provide a bit-wise definitions and use them here
> instead of GENMASK().
> 
> ...
> 
> > +	case IIO_CHAN_INFO_SCALE:
> > +		/* Raw pressure is in Pa; scale to kPa per IIO ABI */
> > +		*val = 1;
> > +		*val2 = 1000;  
> 
> So, we have KILO in units.h.
> 
> > +		return IIO_VAL_FRACTIONAL;  
>