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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>
This commit is contained in:
Lars-Peter Clausen 2012-09-10 09:34:00 +01:00 committed by Jonathan Cameron
parent fcc7800b65
commit 93e33d7030
2 changed files with 7 additions and 12 deletions
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5
drivers/staging/iio/adc/ad7476.h
View File

@ -33,8 +33,11 @@ struct ad7476_state {
/*
* 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 {

14
drivers/staging/iio/adc/ad7476_ring.c
View File

@ -26,28 +26,20 @@ static irqreturn_t ad7476_trigger_handler(int irq, void *p)
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;
}