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

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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: 1f25ca11d8 ("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>
This commit is contained in:
David Lechner 2025-07-21 18:04:04 -05:00 committed by Jonathan Cameron
parent 1cfb22c277
commit ae5bc07ec9
1 changed files with 16 additions and 10 deletions
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26
drivers/iio/temperature/maxim_thermocouple.c
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@ -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));
}