Input: adc-joystick - add polled input device support

Add polled input device support to the adc-joystick driver. This is
useful for devices which do not have hardware capable triggers on
their SARADC. Code modified from adc-joystick.c changes made by Maya
Matuszczyk.

Signed-off-by: Maya Matuszczyk <[e-mail]>
Signed-off-by: Chris Morgan <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/joystick/adc-joystick.c

···
 	struct adc_joystick_axis *axes;
 	struct iio_channel *chans;
 	int num_chans;
+	bool polled;
 };
+
+static void adc_joystick_poll(struct input_dev *input)
+{
+	struct adc_joystick *joy = input_get_drvdata(input);
+	int i, val, ret;
+
+	for (i = 0; i < joy->num_chans; i++) {
+		ret = iio_read_channel_raw(&joy->chans[i], &val);
+		if (ret < 0)
+			return;
+		input_report_abs(input, joy->axes[i].code, val);
+	}
+	input_sync(input);
+}
 
 static int adc_joystick_handle(const void *data, void *private)
 {
···
 	int error;
 	int bits;
 	int i;
+	unsigned int poll_interval;
 
 	joy = devm_kzalloc(dev, sizeof(*joy), GFP_KERNEL);
 	if (!joy)
···
 		return error;
 	}
 
-	/* Count how many channels we got. NULL terminated. */
+	error = device_property_read_u32(dev, "poll-interval", &poll_interval);
+	if (error) {
+		/* -EINVAL means the property is absent. */
+		if (error != -EINVAL)
+			return error;
+	} else if (poll_interval == 0) {
+		dev_err(dev, "Unable to get poll-interval\n");
+		return -EINVAL;
+	} else {
+		joy->polled = true;
+	}
+
+	/*
+	 * Count how many channels we got. NULL terminated.
+	 * Do not check the storage size if using polling.
+	 */
 	for (i = 0; joy->chans[i].indio_dev; i++) {
+		if (joy->polled)
+			continue;
 		bits = joy->chans[i].channel->scan_type.storagebits;
 		if (!bits || bits > 16) {
 			dev_err(dev, "Unsupported channel storage size\n");
···
 	joy->input = input;
 	input->name = pdev->name;
 	input->id.bustype = BUS_HOST;
-	input->open = adc_joystick_open;
-	input->close = adc_joystick_close;
 
 	error = adc_joystick_set_axes(dev, joy);
 	if (error)
 		return error;
 
-	joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle, joy);
-	if (IS_ERR(joy->buffer)) {
-		dev_err(dev, "Unable to allocate callback buffer\n");
-		return PTR_ERR(joy->buffer);
-	}
+	if (joy->polled) {
+		input_setup_polling(input, adc_joystick_poll);
+		input_set_poll_interval(input, poll_interval);
+	} else {
+		input->open = adc_joystick_open;
+		input->close = adc_joystick_close;
 
-	error = devm_add_action_or_reset(dev, adc_joystick_cleanup, joy->buffer);
-	if (error)  {
-		dev_err(dev, "Unable to add action\n");
-		return error;
+		joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle,
+						     joy);
+		if (IS_ERR(joy->buffer)) {
+			dev_err(dev, "Unable to allocate callback buffer\n");
+			return PTR_ERR(joy->buffer);
+		}
+
+		error = devm_add_action_or_reset(dev, adc_joystick_cleanup,
+						 joy->buffer);
+		if (error)  {
+			dev_err(dev, "Unable to add action\n");
+			return error;
+		}
 	}
 
 	input_set_drvdata(input, joy);