staging: iio: resolver: ad2s1210: convert fexcit to channel attribute

The ad2s1210 driver has a device-specific attribute `fexcit` for setting
the frequency of the excitation output. This converts it to a channel in
order to use standard IIO ABI.

The excitation frequency is an analog output that generates a sine wave.
Only the frequency is configurable. According to the datasheet, the
specified range of the excitation frequency is from 2 kHz to 20 kHz and
can be set in increments of 250 Hz.
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20231005-ad2s1210-mainline-v4-3-ec00746840fc@baylibre.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/resolver/ad2s1210.c

@@ -227,54 +227,6 @@ static int ad2s1210_set_resolution_gpios(struct ad2s1210_state *st,
 				     bitmap);
 }
 
-static ssize_t ad2s1210_show_fexcit(struct device *dev,
-				    struct device_attribute *attr,
-				    char *buf)
-{
-	struct ad2s1210_state *st = iio_priv(dev_to_iio_dev(dev));
-	unsigned int value;
-	u16 fexcit;
-	int ret;
-
-	mutex_lock(&st->lock);
-	ret = regmap_read(st->regmap, AD2S1210_REG_EXCIT_FREQ, &value);
-	if (ret < 0)
-		goto error_ret;
-
-	fexcit = value * st->clkin_hz / (1 << 15);
-
-	ret = sprintf(buf, "%u\n", fexcit);
-
-error_ret:
-	mutex_unlock(&st->lock);
-	return ret;
-}
-
-static ssize_t ad2s1210_store_fexcit(struct device *dev,
-				     struct device_attribute *attr,
-				     const char *buf, size_t len)
-{
-	struct ad2s1210_state *st = iio_priv(dev_to_iio_dev(dev));
-	u16 fexcit;
-	int ret;
-
-	ret = kstrtou16(buf, 10, &fexcit);
-	if (ret < 0 || fexcit < AD2S1210_MIN_EXCIT || fexcit > AD2S1210_MAX_EXCIT)
-		return -EINVAL;
-
-	mutex_lock(&st->lock);
-	ret = ad2s1210_reinit_excitation_frequency(st, fexcit);
-	if (ret < 0)
-		goto error_ret;
-
-	ret = len;
-
-error_ret:
-	mutex_unlock(&st->lock);
-
-	return ret;
-}
-
 static ssize_t ad2s1210_show_resolution(struct device *dev,
 					struct device_attribute *attr,
 					char *buf)
@@ -478,6 +430,38 @@ static int ad2s1210_set_hysteresis(struct ad2s1210_state *st, int val)
 	return ret;
 }
 
+static int ad2s1210_get_excitation_frequency(struct ad2s1210_state *st, int *val)
+{
+	unsigned int reg_val;
+	int ret;
+
+	mutex_lock(&st->lock);
+	ret = regmap_read(st->regmap, AD2S1210_REG_EXCIT_FREQ, &reg_val);
+	if (ret < 0)
+		goto error_ret;
+
+	*val = reg_val * st->clkin_hz / (1 << 15);
+	ret = IIO_VAL_INT;
+
+error_ret:
+	mutex_unlock(&st->lock);
+	return ret;
+}
+
+static int ad2s1210_set_excitation_frequency(struct ad2s1210_state *st, int val)
+{
+	int ret;
+
+	if (val < AD2S1210_MIN_EXCIT || val > AD2S1210_MAX_EXCIT)
+		return -EINVAL;
+
+	mutex_lock(&st->lock);
+	ret = ad2s1210_reinit_excitation_frequency(st, val);
+	mutex_unlock(&st->lock);
+
+	return ret;
+}
+
 static const int ad2s1210_velocity_scale[] = {
 	17089132, /* 8.192MHz / (2*pi * 2500 / 2^15) */
 	42722830, /* 8.192MHz / (2*pi * 1000 / 2^15) */
@@ -510,6 +494,13 @@ static int ad2s1210_read_raw(struct iio_dev *indio_dev,
 		default:
 			return -EINVAL;
 		}
+	case IIO_CHAN_INFO_FREQUENCY:
+		switch (chan->type) {
+		case IIO_ALTVOLTAGE:
+			return ad2s1210_get_excitation_frequency(st, val);
+		default:
+			return -EINVAL;
+		}
 	case IIO_CHAN_INFO_HYSTERESIS:
 		switch (chan->type) {
 		case IIO_ANGL:
@@ -527,9 +518,24 @@ static int ad2s1210_read_avail(struct iio_dev *indio_dev,
 			       const int **vals, int *type,
 			       int *length, long mask)
 {
+	static const int excitation_frequency_available[] = {
+		AD2S1210_MIN_EXCIT,
+		250, /* step */
+		AD2S1210_MAX_EXCIT,
+	};
+
 	struct ad2s1210_state *st = iio_priv(indio_dev);
 
 	switch (mask) {
+	case IIO_CHAN_INFO_FREQUENCY:
+		switch (chan->type) {
+		case IIO_ALTVOLTAGE:
+			*type = IIO_VAL_INT;
+			*vals = excitation_frequency_available;
+			return IIO_AVAIL_RANGE;
+		default:
+			return -EINVAL;
+		}
 	case IIO_CHAN_INFO_HYSTERESIS:
 		switch (chan->type) {
 		case IIO_ANGL:
@@ -552,6 +558,13 @@ static int ad2s1210_write_raw(struct iio_dev *indio_dev,
 	struct ad2s1210_state *st = iio_priv(indio_dev);
 
 	switch (mask) {
+	case IIO_CHAN_INFO_FREQUENCY:
+		switch (chan->type) {
+		case IIO_ALTVOLTAGE:
+			return ad2s1210_set_excitation_frequency(st, val);
+		default:
+			return -EINVAL;
+		}
 	case IIO_CHAN_INFO_HYSTERESIS:
 		switch (chan->type) {
 		case IIO_ANGL:
@@ -564,8 +577,6 @@ static int ad2s1210_write_raw(struct iio_dev *indio_dev,
 	}
 }
 
-static IIO_DEVICE_ATTR(fexcit, 0644,
-		       ad2s1210_show_fexcit,	ad2s1210_store_fexcit, 0);
 static IIO_DEVICE_ATTR(bits, 0644,
 		       ad2s1210_show_resolution, ad2s1210_store_resolution, 0);
 static IIO_DEVICE_ATTR(fault, 0644,
@@ -609,11 +620,19 @@ static const struct iio_chan_spec ad2s1210_channels[] = {
 		.channel = 0,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
 				      BIT(IIO_CHAN_INFO_SCALE),
-	}
+	}, {
+		/* excitation frequency output */
+		.type = IIO_ALTVOLTAGE,
+		.indexed = 1,
+		.channel = 0,
+		.output = 1,
+		.scan_index = -1,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_FREQUENCY),
+		.info_mask_separate_available = BIT(IIO_CHAN_INFO_FREQUENCY),
+	},
 };
 
 static struct attribute *ad2s1210_attributes[] = {
-	&iio_dev_attr_fexcit.dev_attr.attr,
 	&iio_dev_attr_bits.dev_attr.attr,
 	&iio_dev_attr_fault.dev_attr.attr,
 	&iio_dev_attr_los_thrd.dev_attr.attr,