iio: adc: max1027: Allow all kind of triggers to be used

There is no reason to limit this driver to its internal trigger. The
only difference being, when using an external trigger, the sample
conversion must be manually started.

Drop the ->validate_trigger() hook in order to allow other triggers to
be bound.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20210921115408.66711-16-miquel.raynal@bootlin.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/max1027.c

@@ -430,17 +430,6 @@ static int max1027_debugfs_reg_access(struct iio_dev *indio_dev,
 	return spi_write(st->spi, val, 1);
 }
 
-static int max1027_validate_trigger(struct iio_dev *indio_dev,
-				    struct iio_trigger *trig)
-{
-	struct max1027_state *st = iio_priv(indio_dev);
-
-	if (st->trig != trig)
-		return -EINVAL;
-
-	return 0;
-}
-
 static int max1027_set_cnvst_trigger_state(struct iio_trigger *trig, bool state)
 {
 	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
@@ -491,8 +480,8 @@ static irqreturn_t max1027_handler(int irq, void *private)
 	struct max1027_state *st = iio_priv(indio_dev);
 
 	/*
-	 * If buffers are disabled (raw read), we just need to unlock the
-	 * waiters which will then handle the data.
+	 * If buffers are disabled (raw read) or when using external triggers,
+	 * we just need to unlock the waiters which will then handle the data.
 	 *
 	 * When using the internal trigger, we must hand-off the choice of the
 	 * handler to the core which will then lookup through the interrupt tree
@@ -515,7 +504,19 @@ static irqreturn_t max1027_trigger_handler(int irq, void *private)
 	struct iio_dev *indio_dev = pf->indio_dev;
 	int ret;
 
+	if (!iio_trigger_using_own(indio_dev)) {
+		ret = max1027_configure_chans_and_start(indio_dev);
+		if (ret)
+			goto out;
+
+		/* This is a threaded handler, it is fine to wait for an IRQ */
+		ret = max1027_wait_eoc(indio_dev);
+		if (ret)
+			goto out;
+	}
+
 	ret = max1027_read_scan(indio_dev);
+out:
 	if (ret)
 		dev_err(&indio_dev->dev,
 			"Cannot read scanned values (%d)\n", ret);
@@ -532,7 +533,6 @@ static const struct iio_trigger_ops max1027_trigger_ops = {
 
 static const struct iio_info max1027_info = {
 	.read_raw = &max1027_read_raw,
-	.validate_trigger = &max1027_validate_trigger,
 	.debugfs_reg_access = &max1027_debugfs_reg_access,
 };