iio: make stm32 trigger driver use INDIO_HARDWARE_TRIGGERED mode

Add validate function to be use to use the correct trigger.
Add an attribute to configure device mode like for quadrature and
enable modes

Signed-off-by: Benjamin Gaignard <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

Documentation/ABI/testing/sysfs-bus-iio-timer-stm32

···
 			Counting is enabled on rising edge of the connected
 			trigger, and remains enabled for the duration of this
 			selected mode.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_count_trigger_mode_available
+KernelVersion:	4.13
+Contact:	[e-mail]
+Description:
+		Reading returns the list possible trigger modes.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_count0_trigger_mode
+KernelVersion:	4.13
+Contact:	[e-mail]
+Description:
+		Configure the device counter trigger mode
+		counting direction is set by in_count0_count_direction
+		attribute and the counter is clocked by the connected trigger
+		rising edges.

drivers/iio/trigger/stm32-timer-trigger.c

···
 	return -EINVAL;
 }
 
+static int stm32_counter_validate_trigger(struct iio_dev *indio_dev,
+					  struct iio_trigger *trig)
+{
+	struct stm32_timer_trigger *priv = iio_priv(indio_dev);
+	const char * const *cur = priv->valids;
+	unsigned int i = 0;
+
+	if (!is_stm32_timer_trigger(trig))
+		return -EINVAL;
+
+	while (cur && *cur) {
+		if (!strncmp(trig->name, *cur, strlen(trig->name))) {
+			regmap_update_bits(priv->regmap,
+					   TIM_SMCR, TIM_SMCR_TS,
+					   i << TIM_SMCR_TS_SHIFT);
+			return 0;
+		}
+		cur++;
+		i++;
+	}
+
+	return -EINVAL;
+}
+
 static const struct iio_info stm32_trigger_info = {
 	.driver_module = THIS_MODULE,
+	.validate_trigger = stm32_counter_validate_trigger,
 	.read_raw = stm32_counter_read_raw,
 	.write_raw = stm32_counter_write_raw
+};
+
+static const char *const stm32_trigger_modes[] = {
+	"trigger",
+};
+
+static int stm32_set_trigger_mode(struct iio_dev *indio_dev,
+				  const struct iio_chan_spec *chan,
+				  unsigned int mode)
+{
+	struct stm32_timer_trigger *priv = iio_priv(indio_dev);
+
+	regmap_update_bits(priv->regmap, TIM_SMCR, TIM_SMCR_SMS, TIM_SMCR_SMS);
+
+	return 0;
+}
+
+static int stm32_get_trigger_mode(struct iio_dev *indio_dev,
+				  const struct iio_chan_spec *chan)
+{
+	struct stm32_timer_trigger *priv = iio_priv(indio_dev);
+	u32 smcr;
+
+	regmap_read(priv->regmap, TIM_SMCR, &smcr);
+
+	return smcr == TIM_SMCR_SMS ? 0 : -EINVAL;
+}
+
+static const struct iio_enum stm32_trigger_mode_enum = {
+	.items = stm32_trigger_modes,
+	.num_items = ARRAY_SIZE(stm32_trigger_modes),
+	.set = stm32_set_trigger_mode,
+	.get = stm32_get_trigger_mode
 };
 
 static const char *const stm32_enable_modes[] = {
···
 	IIO_ENUM_AVAILABLE("quadrature_mode", &stm32_quadrature_mode_enum),
 	IIO_ENUM("enable_mode", IIO_SEPARATE, &stm32_enable_mode_enum),
 	IIO_ENUM_AVAILABLE("enable_mode", &stm32_enable_mode_enum),
+	IIO_ENUM("trigger_mode", IIO_SEPARATE, &stm32_trigger_mode_enum),
+	IIO_ENUM_AVAILABLE("trigger_mode", &stm32_trigger_mode_enum),
 	{}
 };
 
···
 	indio_dev->name = dev_name(dev);
 	indio_dev->dev.parent = dev;
 	indio_dev->info = &stm32_trigger_info;
+	indio_dev->modes = INDIO_HARDWARE_TRIGGERED;
 	indio_dev->num_channels = 1;
 	indio_dev->channels = &stm32_trigger_channel;
 	indio_dev->dev.of_node = dev->of_node;