iio: gts-helper: add helpers to ease searches of gain_sel and new_gain

This helper functions reduce the burden in the drivers that want to
fetch a gain and time selector for a given scale or a new optimal gain.

The former is currently achieved by calling
iio_gts_find_gain_sel_for_scale_using_time() for the current time
selector, and then iterating over the rest of time selectors if the
gain selector was not found.

The latter requires a combination of multiple iio-gts helpers to find
the new gain, look for an optimal gain if there was no exact match, and
set a minimum gain if the optimal gain is not in the range of available
gains.

Provide simpler workflows by means of functions that address common
patterns in the users of the iio-gts helpers.

Acked-by: Matti Vaittinen <[email protected]>
Signed-off-by: Javier Carrasco <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jonathan Cameron <[email protected]>

Author: javiercarrascocruz

drivers/iio/industrialio-gts-helper.c

@@ -915,6 +915,41 @@ int iio_gts_find_gain_sel_for_scale_using_time(struct iio_gts *gts, int time_sel
 }
 EXPORT_SYMBOL_NS_GPL(iio_gts_find_gain_sel_for_scale_using_time, "IIO_GTS_HELPER");
 
+/**
+ * iio_gts_find_gain_time_sel_for_scale - Fetch gain and time selectors for scale
+ * @gts:	Gain time scale descriptor
+ * @scale_int:	Integral part of the scale (typically val1)
+ * @scale_nano:	Fractional part of the scale (nano or ppb)
+ * @gain_sel:	Pointer to value where gain selector is stored.
+ * @time_sel:	Pointer to value where time selector is stored.
+ *
+ * Wrapper around iio_gts_find_gain_for_scale_using_time() to fetch the
+ * gain and time selectors for a given scale.
+ *
+ * Return: 0 on success and -EINVAL on error.
+ */
+int iio_gts_find_gain_time_sel_for_scale(struct iio_gts *gts, int scale_int,
+					 int scale_nano, int *gain_sel,
+					 int *time_sel)
+{
+	int i, ret;
+
+	for (i = 0; i < gts->num_itime; i++) {
+		*time_sel = gts->itime_table[i].sel;
+		ret = iio_gts_find_gain_sel_for_scale_using_time(gts, *time_sel,
+								 scale_int,
+								 scale_nano,
+								 gain_sel);
+		if (ret)
+			continue;
+
+		return 0;
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_NS_GPL(iio_gts_find_gain_time_sel_for_scale, "IIO_GTS_HELPER");
+
 static int iio_gts_get_total_gain(struct iio_gts *gts, int gain, int time)
 {
 	const struct iio_itime_sel_mul *itime;
@@ -1086,6 +1121,48 @@ int iio_gts_find_new_gain_by_old_gain_time(struct iio_gts *gts, int old_gain,
 }
 EXPORT_SYMBOL_NS_GPL(iio_gts_find_new_gain_by_old_gain_time, "IIO_GTS_HELPER");
 
+/**
+ * iio_gts_find_new_gain_by_gain_time_min - compensate for time change
+ * @gts:	Gain time scale descriptor
+ * @old_gain:	Previously set gain
+ * @old_time:	Selector corresponding previously set time
+ * @new_time:	Selector corresponding new time to be set
+ * @new_gain:	Pointer to value where new gain is to be written
+ * @in_range:	Indicate if the @new_gain was in the range of
+ *		supported gains.
+ *
+ * Wrapper around iio_gts_find_new_gain_by_old_gain_time() that tries to
+ * set an optimal value if no exact match was found, defaulting to the
+ * minimum gain to avoid saturations if the optimal value is not in the
+ * range of supported gains.
+ *
+ * Return: 0 on success and a negative value if no gain was found.
+ */
+int iio_gts_find_new_gain_by_gain_time_min(struct iio_gts *gts, int old_gain,
+					   int old_time, int new_time,
+					   int *new_gain, bool *in_range)
+{
+	int ret;
+
+	*in_range = true;
+	ret = iio_gts_find_new_gain_by_old_gain_time(gts, old_gain, old_time,
+						     new_time, new_gain);
+	if (*new_gain < 0)
+		return -EINVAL;
+
+	if (ret) {
+		*new_gain = iio_find_closest_gain_low(gts, *new_gain, in_range);
+		if (*new_gain < 0) {
+			*new_gain = iio_gts_get_min_gain(gts);
+			if (*new_gain < 0)
+				return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(iio_gts_find_new_gain_by_gain_time_min, "IIO_GTS_HELPER");
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Matti Vaittinen <[email protected]>");
 MODULE_DESCRIPTION("IIO light sensor gain-time-scale helpers");

include/linux/iio/iio-gts-helper.h

@@ -188,6 +188,9 @@ int iio_gts_total_gain_to_scale(struct iio_gts *gts, int total_gain,
 int iio_gts_find_gain_sel_for_scale_using_time(struct iio_gts *gts, int time_sel,
 					       int scale_int, int scale_nano,
 					       int *gain_sel);
+int iio_gts_find_gain_time_sel_for_scale(struct iio_gts *gts, int scale_int,
+					 int scale_nano, int *gain_sel,
+					 int *time_sel);
 int iio_gts_get_scale(struct iio_gts *gts, int gain, int time, int *scale_int,
 		      int *scale_nano);
 int iio_gts_find_new_gain_sel_by_old_gain_time(struct iio_gts *gts,
@@ -196,6 +199,9 @@ int iio_gts_find_new_gain_sel_by_old_gain_time(struct iio_gts *gts,
 int iio_gts_find_new_gain_by_old_gain_time(struct iio_gts *gts, int old_gain,
 					   int old_time, int new_time,
 					   int *new_gain);
+int iio_gts_find_new_gain_by_gain_time_min(struct iio_gts *gts, int old_gain,
+					   int old_time, int new_time,
+					   int *new_gain, bool *in_range);
 int iio_gts_avail_times(struct iio_gts *gts,  const int **vals, int *type,
 			int *length);
 int iio_gts_all_avail_scales(struct iio_gts *gts, const int **vals, int *type,