On 09/07/2012 02:44 PM, Lars-Peter Clausen wrote:
> 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@xxxxxxxxxx>
> ---
> drivers/staging/iio/adc/ad7476.h | 5 ++++-
> drivers/staging/iio/adc/ad7476_ring.c | 13 +++----------
> 2 files changed, 7 insertions(+), 11 deletions(-)
>
> 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 @@ 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 {
> diff --git a/drivers/staging/iio/adc/ad7476_ring.c b/drivers/staging/iio/adc/ad7476_ring.c
> index 940681f..185cfde 100644
> --- a/drivers/staging/iio/adc/ad7476_ring.c
> +++ b/drivers/staging/iio/adc/ad7476_ring.c
> @@ -26,14 +26,9 @@ 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,
> + b_sent = spi_read(st->spi, st->data,
> st->chip_info->channel[0].scan_type.storagebits / 8);
I just noticed this can even more be simplified by using the prepared SPI
message. Unfortunately this will require regeneration of a few more patches.
I'll resend the whole series next week, after it had some exposure to review.
> if (b_sent < 0)
> goto done;
> @@ -41,13 +36,11 @@ static irqreturn_t ad7476_trigger_handler(int irq, void *p)
> 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;
> }
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