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Commit 93e33d70 authored by Lars-Peter Clausen's avatar Lars-Peter Clausen Committed by Jonathan Cameron
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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: default avatarLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
parent fcc7800b

drivers/staging/iio/adc/ad7476.h

+4 −1
Original line number Diff line number Diff line
@@ -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 {

drivers/staging/iio/adc/ad7476_ring.c

+3 −11
Original line number Diff line number Diff line
@@ -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;

}