iio: temperature: maxim_thermocouple: use DMA-safe buffer for spi_read()

Replace using stack-allocated buffers with a DMA-safe buffer for use
with spi_read(). This allows the driver to be safely used with
DMA-enabled SPI controllers.

The buffer array is also converted to a struct with a union to make the
usage of the memory in the buffer more clear and ensure proper alignment.

Fixes: 1f25ca11d84a ("iio: temperature: add support for Maxim thermocouple chips")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://patch.msgid.link/20250721-iio-use-more-iio_declare_buffer_with_ts-3-v2-1-0c68d41ccf6c@baylibre.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/temperature/maxim_thermocouple.c b/drivers/iio/temperature/maxim_thermocouple.c
index cae8e84821d7fd521d59432580d51def939fa4d1..205939680fd4fcdb1024ee8e048f979522fa7505 100644 (file)
--- a/drivers/iio/temperature/maxim_thermocouple.c
+++ b/drivers/iio/temperature/maxim_thermocouple.c
@@ -11,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/err.h>
 #include <linux/spi/spi.h>
+#include <linux/types.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
 #include <linux/iio/trigger.h>
@@ -121,8 +122,15 @@ struct maxim_thermocouple_data {
        struct spi_device *spi;
        const struct maxim_thermocouple_chip *chip;
        char tc_type;
-
-       u8 buffer[16] __aligned(IIO_DMA_MINALIGN);
+       /* Buffer for reading up to 2 hardware channels. */
+       struct {
+               union {
+                       __be16 raw16;
+                       __be32 raw32;
+                       __be16 raw[2];
+               };
+               aligned_s64 timestamp;
+       } buffer __aligned(IIO_DMA_MINALIGN);
 };
 
 static int maxim_thermocouple_read(struct maxim_thermocouple_data *data,
@@ -130,18 +138,16 @@ static int maxim_thermocouple_read(struct maxim_thermocouple_data *data,
 {
        unsigned int storage_bytes = data->chip->read_size;
        unsigned int shift = chan->scan_type.shift + (chan->address * 8);
-       __be16 buf16;
-       __be32 buf32;
        int ret;
 
        switch (storage_bytes) {
        case 2:
-               ret = spi_read(data->spi, (void *)&buf16, storage_bytes);
-               *val = be16_to_cpu(buf16);
+               ret = spi_read(data->spi, &data->buffer.raw16, storage_bytes);
+               *val = be16_to_cpu(data->buffer.raw16);
                break;
        case 4:
-               ret = spi_read(data->spi, (void *)&buf32, storage_bytes);
-               *val = be32_to_cpu(buf32);
+               ret = spi_read(data->spi, &data->buffer.raw32, storage_bytes);
+               *val = be32_to_cpu(data->buffer.raw32);
                break;
        default:
                ret = -EINVAL;
@@ -166,9 +172,9 @@ static irqreturn_t maxim_thermocouple_trigger_handler(int irq, void *private)
        struct maxim_thermocouple_data *data = iio_priv(indio_dev);
        int ret;
 
-       ret = spi_read(data->spi, data->buffer, data->chip->read_size);
+       ret = spi_read(data->spi, data->buffer.raw, data->chip->read_size);
        if (!ret) {
-               iio_push_to_buffers_with_ts(indio_dev, data->buffer,
+               iio_push_to_buffers_with_ts(indio_dev, &data->buffer,
                                            sizeof(data->buffer),
                                            iio_get_time_ns(indio_dev));
        }