Re: [PATCH v7 3/6] iio: adc: ad4691: add triggered buffer support

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 12 Apr 2026 18:43:01 +0100
Jonathan Cameron <jic23@kernel.org> wrote:

> On Fri, 10 Apr 2026 15:46:36 -0500
> David Lechner <dlechner@baylibre.com> wrote:
> 
> > On 4/9/26 10:28 AM, Radu Sabau via B4 Relay wrote:  
> > > From: Radu Sabau <radu.sabau@analog.com>
> > > 
> > > Add buffered capture support using the IIO triggered buffer framework.
> > >     
> > 
> > ...
> >   
> > > @@ -201,8 +245,45 @@ struct ad4691_state {
> > >  	 * atomicity of consecutive SPI operations.
> > >  	 */
> > >  	struct mutex lock;
> > > +	/*
> > > +	 * Per-buffer-enable lifetime resources:
> > > +	 * Manual Mode - a pre-built SPI message that clocks out N+1
> > > +	 *		 transfers in one go.
> > > +	 * CNV Burst Mode - a pre-built SPI message that clocks out 2*N
> > > +	 *		    transfers in one go.
> > > +	 */
> > > +	struct spi_message scan_msg;
> > > +	/* max 16 + 1 NOOP (manual) or 2*16 + 2 (CNV burst). */
> > > +	struct spi_transfer scan_xfers[34];
> > > +	/*
> > > +	 * CNV burst: 16 AVG_IN addresses + state-reset address + state-reset
> > > +	 * value = 18.  Manual: 16 channel cmds + 1 NOOP = 17.
> > > +	 */
> > > +	__be16 scan_tx[18];    
> > 
> > Needs __aligned(IIO_DMA_MINALIGN) since it is used with SPI.  
> As below.
> >   
> > > +	/* Scan buffer: one BE16 slot per channel (rx'd directly), plus timestamp */
> > > +	struct {
> > > +		__be16 vals[16];
> > > +		aligned_s64 ts;
> > > +	} scan;    
> > 
> > Unless it is required that all channels are always enabled:
> > 
> > 	IIO_DECLARE_BUFFER_WITH_TS(__be16, scan_rx, 16);
> > 
> > In any case, needs to be DMA-safe for SPI.  
> Custom regmap that uses spi_write_then_read() for all cases so it
> should be bounced anyway.
> 
> Perhaps a comment to that affect would be useful.
> 
Ignore that.  It's an optimized spi message. oops.

> J
>