iio: adc: ad7606: explicit timestamp alignment

Use struct with aligned_s64 timestamp to make timestamp alignment
explicit. Technically, what we have works because for all known
architectures, IIO_DMA_MINALIGN is a multiple of __alignof__(s64).
But this way, we don't have to make people read the comments to know
why there are extra elements in each buffer.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://patch.msgid.link/20250428-iio-adc-ad7606-fix-buffer-alignment-v1-1-88dfc57e5df0@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/ad7606.h b/drivers/iio/adc/ad7606.h
index 89d4955..441e62c 100644 (file)
--- a/drivers/iio/adc/ad7606.h
+++ b/drivers/iio/adc/ad7606.h
@@ -155,12 +155,15 @@ struct ad7606_state {
        /*
         * DMA (thus cache coherency maintenance) may require the
         * transfer buffers to live in their own cache lines.
-        * 16 * 16-bit samples + 64-bit timestamp - for AD7616
-        * 8 * 32-bit samples + 64-bit timestamp - for AD7616C-18 (and similar)
+        * 16 * 16-bit samples for AD7616
+        * 8 * 32-bit samples for AD7616C-18 (and similar)
         */
-       union {
-               u16 buf16[20];
-               u32 buf32[10];
+       struct {
+               union {
+                       u16 buf16[16];
+                       u32 buf32[8];
+               };
+               aligned_s64 timestamp;
        } data __aligned(IIO_DMA_MINALIGN);
        __be16                          d16[2];
 };