| Message ID | 1531409786-20180-1-git-send-email-stefan.popa@analog.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Jul 12, 2018 at 6:36 PM, Stefan Popa <stefan.popa@analog.com> wrote: > This patch adds the option for the user to select the sampling frequency. > Also, the user can read the available frequencies and read the currently > set frequency via the read_raw function. The frequency can be set via the > write_raw function. > > When the frequency is set, the bandwidth is also checked and ensured > that it is constrained to at most half of the sampling frequency. > +static int adxl372_find_closest_match(const int *array, > + unsigned int size, int val) > +{ > + int i; > + > + for (i = 0; i < size; i++) { > + if (val <= array[i]) > + return i; > + } > + > + return size - 1; > +} Perhaps it's time to extend bsearch with something called bsearch_closest().
On 07/12/2018 08:25 PM, Andy Shevchenko wrote: > On Thu, Jul 12, 2018 at 6:36 PM, Stefan Popa <stefan.popa@analog.com> wrote: >> This patch adds the option for the user to select the sampling frequency. >> Also, the user can read the available frequencies and read the currently >> set frequency via the read_raw function. The frequency can be set via the >> write_raw function. >> >> When the frequency is set, the bandwidth is also checked and ensured >> that it is constrained to at most half of the sampling frequency. > >> +static int adxl372_find_closest_match(const int *array, >> + unsigned int size, int val) >> +{ >> + int i; >> + >> + for (i = 0; i < size; i++) { >> + if (val <= array[i]) >> + return i; >> + } >> + >> + return size - 1; >> +} > > Perhaps it's time to extend bsearch with something called > bsearch_closest(). > While it makes sense to have a helper function for this the generic bsearch is not a good solution for small arrays. The generated code is probably larger and the function call overhead of calling the cmp function completely outweighs the savings from doing a binary search. bsearch() is good if your array has 100s or 1000s of entries. If it only has 5, not so much. -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/iio/accel/adxl372.c b/drivers/iio/accel/adxl372.c index 645902d..498c740 100644 --- a/drivers/iio/accel/adxl372.c +++ b/drivers/iio/accel/adxl372.c @@ -205,7 +205,8 @@ static const int adxl372_samp_freq_tbl[5] = { .modified = 1, \ .channel2 = IIO_MOD_##axis, \ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \ - .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \ + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) | \ + BIT(IIO_CHAN_INFO_SAMP_FREQ), \ .scan_index = index, \ .scan_type = { \ .sign = 's', \ @@ -291,6 +292,19 @@ static int adxl372_set_odr(struct adxl372_state *st, return ret; } +static int adxl372_find_closest_match(const int *array, + unsigned int size, int val) +{ + int i; + + for (i = 0; i < size; i++) { + if (val <= array[i]) + return i; + } + + return size - 1; +} + static int adxl372_set_bandwidth(struct adxl372_state *st, enum adxl372_bandwidth bw) { @@ -568,6 +582,37 @@ static int adxl372_read_raw(struct iio_dev *indio_dev, *val = 0; *val2 = ADXL372_USCALE; return IIO_VAL_INT_PLUS_MICRO; + case IIO_CHAN_INFO_SAMP_FREQ: + *val = adxl372_samp_freq_tbl[st->odr]; + return IIO_VAL_INT; + } + + return -EINVAL; +} + +static int adxl372_write_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + int val, int val2, long info) +{ + struct adxl372_state *st = iio_priv(indio_dev); + int odr_index, ret; + + switch (info) { + case IIO_CHAN_INFO_SAMP_FREQ: + odr_index = adxl372_find_closest_match(adxl372_samp_freq_tbl, + ARRAY_SIZE(adxl372_samp_freq_tbl), + val); + ret = adxl372_set_odr(st, odr_index); + if (ret < 0) + return ret; + /* + * The maximum bandwidth is constrained to at most half of + * the ODR to ensure that the Nyquist criteria is not violated + */ + if (st->bw > odr_index) + ret = adxl372_set_bandwidth(st, odr_index); + + return ret; default: return -EINVAL; } @@ -722,8 +767,21 @@ static const struct iio_trigger_ops adxl372_trigger_ops = { .set_trigger_state = adxl372_dready_trig_set_state, }; +static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("400 800 1600 3200 6400"); + +static struct attribute *adxl372_attributes[] = { + &iio_const_attr_sampling_frequency_available.dev_attr.attr, + NULL, +}; + +static const struct attribute_group adxl372_attrs_group = { + .attrs = adxl372_attributes, +}; + static const struct iio_info adxl372_info = { + .attrs = &adxl372_attrs_group, .read_raw = adxl372_read_raw, + .write_raw = adxl372_write_raw, .debugfs_reg_access = &adxl372_reg_access, .hwfifo_set_watermark = adxl372_set_watermark, };
This patch adds the option for the user to select the sampling frequency. Also, the user can read the available frequencies and read the currently set frequency via the read_raw function. The frequency can be set via the write_raw function. When the frequency is set, the bandwidth is also checked and ensured that it is constrained to at most half of the sampling frequency. Signed-off-by: Stefan Popa <stefan.popa@analog.com> --- drivers/iio/accel/adxl372.c | 60 ++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 59 insertions(+), 1 deletion(-)