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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>
This commit is contained in:
Lars-Peter Clausen 2012-11-05 09:56:00 +00:00 committed by Jonathan Cameron
parent 3c7f0c2b11
commit bd6880477a
2 changed files with 6 additions and 15 deletions
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6
drivers/staging/iio/adc/ad7887.h
View File

@ -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 {

15
drivers/staging/iio/adc/ad7887_ring.c
View File

@ -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;