staging:iio:ad7476: Avoid alloc/free for each sample in buffered mode
The ad7476 driver has only support for 1 channel ADCs. So the upper limit for
the buffer size is the size of one sample plus the size of the timestamp.
Preallocate a buffer large enough to hold this to avoid having to allocate and
free a new buffer for each sample being captured.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/staging/iio/adc/ad7476.h b/drivers/staging/iio/adc/ad7476.h
index 6085fad..c4f1150 100644
--- a/drivers/staging/iio/adc/ad7476.h
+++ b/drivers/staging/iio/adc/ad7476.h
@@ -33,8 +33,11 @@
/*
* DMA (thus cache coherency maintenance) requires the
* transfer buffers to live in their own cache lines.
+ * Make the buffer large enough for one 16 bit sample and one 64 bit
+ * aligned 64 bit timestamp.
*/
- unsigned char data[2] ____cacheline_aligned;
+ unsigned char data[ALIGN(2, sizeof(s64)) + sizeof(s64)]
+ ____cacheline_aligned;
};
enum ad7476_supported_device_ids {
diff --git a/drivers/staging/iio/adc/ad7476_ring.c b/drivers/staging/iio/adc/ad7476_ring.c
index 940681f..3c869b0 100644
--- a/drivers/staging/iio/adc/ad7476_ring.c
+++ b/drivers/staging/iio/adc/ad7476_ring.c
@@ -26,28 +26,20 @@
struct iio_dev *indio_dev = pf->indio_dev;
struct ad7476_state *st = iio_priv(indio_dev);
s64 time_ns;
- __u8 *rxbuf;
int b_sent;
- rxbuf = kzalloc(indio_dev->scan_bytes, GFP_KERNEL);
- if (rxbuf == NULL)
- goto done;
-
- b_sent = spi_read(st->spi, rxbuf,
- st->chip_info->channel[0].scan_type.storagebits / 8);
+ b_sent = spi_sync(st->spi, &st->msg);
if (b_sent < 0)
goto done;
time_ns = iio_get_time_ns();
if (indio_dev->scan_timestamp)
- memcpy(rxbuf + indio_dev->scan_bytes - sizeof(s64),
- &time_ns, sizeof(time_ns));
+ ((s64 *)st->data)[1] = time_ns;
- iio_push_to_buffer(indio_dev->buffer, rxbuf);
+ iio_push_to_buffer(indio_dev->buffer, st->data);
done:
iio_trigger_notify_done(indio_dev->trig);
- kfree(rxbuf);
return IRQ_HANDLED;
}