staging:iio:ad7887: Preallocate sample buffer

We know that the sample buffer will at most need to hold two 16 bit samples and
the 64 bit aligned 64 bit timestamp. Preallocate a buffer large enough to hold
this instead of allocating and freeing it each time a sample is read.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/staging/iio/adc/ad7887.h b/drivers/staging/iio/adc/ad7887.h
index 2e09e54fc9c535c3d61371ba1495a2e5e69ea772..71e50925e066fefb800ced2996e53c6c36398652 100644 (file)
--- a/drivers/staging/iio/adc/ad7887.h
+++ b/drivers/staging/iio/adc/ad7887.h
@@ -72,9 +72,11 @@ struct ad7887_state {
        /*
         * DMA (thus cache coherency maintenance) requires the
         * transfer buffers to live in their own cache lines.
+        * Buffer needs to be large enough to hold two 16 bit samples and a
+        * 64 bit aligned 64 bit timestamp.
         */
-
-       unsigned char                   data[4] ____cacheline_aligned;
+       unsigned char data[ALIGN(4, sizeof(s64)) + sizeof(s64)]
+               ____cacheline_aligned;
 };
 
 enum ad7887_supported_device_ids {

diff --git a/drivers/staging/iio/adc/ad7887_ring.c b/drivers/staging/iio/adc/ad7887_ring.c
index b39923bbeedccf49e7364ed94b32c3ebbbdaf1ce..f11925e62cdcfcbc17fbd4982284e1d76ad6e008 100644 (file)
--- a/drivers/staging/iio/adc/ad7887_ring.c
+++ b/drivers/staging/iio/adc/ad7887_ring.c
@@ -73,31 +73,20 @@ static irqreturn_t ad7887_trigger_handler(int irq, void *p)
        struct iio_dev *indio_dev = pf->indio_dev;
        struct ad7887_state *st = iio_priv(indio_dev);
        s64 time_ns;
-       __u8 *buf;
        int b_sent;
 
-       unsigned int bytes = bitmap_weight(indio_dev->active_scan_mask,
-                                          indio_dev->masklength) *
-               st->chip_info->channel[0].scan_type.storagebits / 8;
-
-       buf = kzalloc(indio_dev->scan_bytes, GFP_KERNEL);
-       if (buf == NULL)
-               goto done;
-
        b_sent = spi_sync(st->spi, st->ring_msg);
        if (b_sent)
                goto done;
 
        time_ns = iio_get_time_ns();
 
-       memcpy(buf, st->data, bytes);
        if (indio_dev->scan_timestamp)
-               memcpy(buf + indio_dev->scan_bytes - sizeof(s64),
+               memcpy(st->data + indio_dev->scan_bytes - sizeof(s64),
                       &time_ns, sizeof(time_ns));
 
-       iio_push_to_buffer(indio_dev->buffer, buf);
+       iio_push_to_buffer(indio_dev->buffer, st->data);
 done:
-       kfree(buf);
        iio_trigger_notify_done(indio_dev->trig);
 
        return IRQ_HANDLED;