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Subject[PATCH 3/4] iio: light: vl6180: Cleanup als_gain lookup, avoid register readback
Date
Instead of manually iterating the array of allowed gain values, use
find_closest. Storing the current gain setting avoids accessing the
hardware on each query.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
---
drivers/iio/light/vl6180.c | 85 ++++++++++++++++++++++++----------------------
1 file changed, 44 insertions(+), 41 deletions(-)

diff --git a/drivers/iio/light/vl6180.c b/drivers/iio/light/vl6180.c
index ae768c832d66..fcd8ef511bdc 100644
--- a/drivers/iio/light/vl6180.c
+++ b/drivers/iio/light/vl6180.c
@@ -24,6 +24,7 @@
#include <linux/err.h>
#include <linux/of.h>
#include <linux/delay.h>
+#include <linux/util_macros.h>

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
@@ -86,6 +87,7 @@
struct vl6180_data {
struct i2c_client *client;
struct mutex lock;
+ unsigned int als_gain_milli;
unsigned int als_it_ms;
};

@@ -276,19 +278,17 @@ static const struct iio_chan_spec vl6180_channels[] = {
};

/*
- * Columns 3 & 4 represent the same value in decimal and hex notations.
- * Kept in order to avoid the datatype conversion while reading the
- * hardware_gain.
+ * Available Ambient Light Sensor gain settings, 1/1000th, and
+ * corresponding setting for the VL6180_ALS_GAIN register
*/
-static const int vl6180_als_gain[8][4] = {
- { 1, 0, 70, VL6180_ALS_GAIN_1 },
- { 1, 250000, 69, VL6180_ALS_GAIN_1_25 },
- { 1, 670000, 68, VL6180_ALS_GAIN_1_67 },
- { 2, 500000, 67, VL6180_ALS_GAIN_2_5 },
- { 5, 0, 66, VL6180_ALS_GAIN_5 },
- { 10, 0, 65, VL6180_ALS_GAIN_10 },
- { 20, 0, 64, VL6180_ALS_GAIN_20 },
- { 40, 0, 71, VL6180_ALS_GAIN_40 }
+static const int vl6180_als_gain_tab[8] = {
+ 1000, 1250, 1670, 2500, 5000, 10000, 20000, 40000
+};
+static const u8 vl6180_als_gain_tab_bits[8] = {
+ VL6180_ALS_GAIN_1, VL6180_ALS_GAIN_1_25,
+ VL6180_ALS_GAIN_1_67, VL6180_ALS_GAIN_2_5,
+ VL6180_ALS_GAIN_5, VL6180_ALS_GAIN_10,
+ VL6180_ALS_GAIN_20, VL6180_ALS_GAIN_40
};

static int vl6180_read_raw(struct iio_dev *indio_dev,
@@ -296,7 +296,7 @@ static int vl6180_read_raw(struct iio_dev *indio_dev,
int *val, int *val2, long mask)
{
struct vl6180_data *data = iio_priv(indio_dev);
- int ret, i;
+ int ret;

switch (mask) {
case IIO_CHAN_INFO_RAW:
@@ -328,17 +328,11 @@ static int vl6180_read_raw(struct iio_dev *indio_dev,

return IIO_VAL_INT_PLUS_MICRO;
case IIO_CHAN_INFO_HARDWAREGAIN:
- ret = vl6180_read_byte(data->client, VL6180_ALS_GAIN);
- if (ret < 0)
- return -EINVAL;
- for (i = 0; i < ARRAY_SIZE(vl6180_als_gain); i++) {
- if (ret == vl6180_als_gain[i][2]) {
- *val = vl6180_als_gain[i][0];
- *val2 = vl6180_als_gain[i][1];
- }
- }
+ *val = data->als_gain_milli;
+ *val2 = 1000;
+
+ return IIO_VAL_FRACTIONAL;

- return IIO_VAL_INT_PLUS_MICRO;
default:
return -EINVAL;
}
@@ -364,25 +358,33 @@ static int vl6180_hold(struct vl6180_data *data, bool hold)

static int vl6180_set_als_gain(struct vl6180_data *data, int val, int val2)
{
- int i, ret;
-
- for (i = 0; i < ARRAY_SIZE(vl6180_als_gain); i++) {
- if (val == vl6180_als_gain[i][0] &&
- val2 == vl6180_als_gain[i][1]) {
- mutex_lock(&data->lock);
- ret = vl6180_hold(data, true);
- if (ret < 0)
- goto fail;
- ret = vl6180_write_byte(data->client, VL6180_ALS_GAIN,
- vl6180_als_gain[i][3]);
-fail:
- vl6180_hold(data, false);
- mutex_unlock(&data->lock);
- return ret;
- }
- }
+ int i, ret, gain;
+
+ if (val < 1 || val > 40)
+ return -EINVAL;
+
+ gain = (val * 1000000 + val2)/1000;
+ if (gain < 1 || gain > 40000)
+ return -EINVAL;
+
+ i = find_closest(gain, vl6180_als_gain_tab,
+ ARRAY_SIZE(vl6180_als_gain_tab));
+
+ mutex_lock(&data->lock);
+ ret = vl6180_hold(data, true);
+ if (ret < 0)
+ goto fail;

- return -EINVAL;
+ ret = vl6180_write_byte(data->client, VL6180_ALS_GAIN,
+ vl6180_als_gain_tab_bits[i]);
+
+ if (ret >= 0)
+ data->als_gain_milli = vl6180_als_gain_tab[i];
+
+fail:
+ vl6180_hold(data, false);
+ mutex_unlock(&data->lock);
+ return ret;
}

static int vl6180_set_it(struct vl6180_data *data, int val, int val2)
@@ -480,6 +482,7 @@ static int vl6180_init(struct vl6180_data *data)
return ret;

/* ALS gain: 1 */
+ data->als_gain_milli = 1000;
ret = vl6180_write_byte(client, VL6180_ALS_GAIN, VL6180_ALS_GAIN_1);
if (ret < 0)
return ret;
--
2.14.1
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