On 09/07/2012 05:37 PM, Lars-Peter Clausen wrote:
> 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.
Sensible move...
>>
>> 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.
Hmm. Guess that would be a marginal improvement. Actually from code
readability I'd be tempted to drop the prepared SPI message and
just do the spi_read as you have it here where that message is currently used.
Obviously it'll have some overhead though so up to you which way you go.
>
>> 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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