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

Jonathan Cameron
2026-04-12T17:44:25Z

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
>