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SubjectRe: [PATCH v2 4/4] iio: accel: adxl345: Add support for triggered buffer
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On 02/05/17 13:23, Eva Rachel Retuya wrote:
> On Mon, May 01, 2017 at 01:42:29AM +0100, Jonathan Cameron wrote:
> [...]
>> Few minor bits inline... I'm a little bit in two minds about the
>> holding up waiting for new data when using another trigger...
>>
>> Jonathan
> [...]
>>> static int adxl345_read_raw(struct iio_dev *indio_dev,
>>> @@ -127,6 +151,10 @@ static int adxl345_read_raw(struct iio_dev *indio_dev,
>>>
>>> switch (mask) {
>>> case IIO_CHAN_INFO_RAW:
>>> + ret = iio_device_claim_direct_mode(indio_dev);
>>> + if (ret)
>>> + return ret;
>>> +
>>> mutex_lock(&data->lock);
>>> ret = adxl345_set_mode(data, ADXL345_POWER_CTL_MEASURE);
>>> if (ret < 0) {
>>> @@ -148,12 +176,14 @@ static int adxl345_read_raw(struct iio_dev *indio_dev,
>>> ret = regmap_bulk_read(data->regmap, chan->address, &regval,
>>> sizeof(regval));
>>> mutex_unlock(&data->lock);
>>> + iio_device_release_direct_mode(indio_dev);
>>> if (ret < 0) {
>>> adxl345_set_mode(data, ADXL345_POWER_CTL_STANDBY);
>>> return ret;
>>> }
>>>
>>> - *val = sign_extend32(le16_to_cpu(regval), 12);
>>> + *val = sign_extend32(le16_to_cpu(regval),
>>> + chan->scan_type.realbits - 1)
>> This change isn't really needed, but I suppose it does little harm...
>>
>>> adxl345_set_mode(data, ADXL345_POWER_CTL_STANDBY);
>>>
>>> return IIO_VAL_INT;
>>> @@ -186,6 +216,64 @@ static irqreturn_t adxl345_irq(int irq, void *p)
>>> return IRQ_NONE;
>>> }
>>>
>>> +static irqreturn_t adxl345_trigger_handler(int irq, void *p)
>>> +{
>>> + struct iio_poll_func *pf = p;
>>> + struct iio_dev *indio_dev = pf->indio_dev;
>>> + struct adxl345_data *data = iio_priv(indio_dev);
>>> + int ret;
>>> +
>>> + mutex_lock(&data->lock);
>>> + /* Make sure data is ready when using external trigger */
>> I 'think' this is only really relevant for the very first one.
>> After that general rule of thumb is that if an external trigger
>> is too quick - bad luck you'll get repeated data.
>>
>> One of the reasons we would want to use another trigger is to
>> support capture in parallel from several sensors - if we 'hold'
>> like this we'll get out of sync.
>>
>> As such I wonder if a better strategy would be to 'hold' for the
>> first reading in the buffer enable - thus guaranteeing valid
>> data before we start. After that we wouldn't need to check this
>> here.
>>
>
> Thanks for the explanation. If we are to go with this one, where to put
> it, preenable or postenable? I'm assuming the latter but would like to
> confirm.

postenable. It could in theory be effected by a future use of the
update_scan_mode callback so should be after that.

J
>
>> What do others think?
>>
>
> Any other inputs are greatly appreciated.
>
> Eva
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