iio: trigger: Print an error if there is no available irq

If there are more trigger consumers than
CONFIG_IIO_CONSUMERS_PER_TRIGGER, iio_trigger_attach_poll_func will
silently fail. Add an error message to inform the user that
CONFIG_IIO_CONSUMERS_PER_TRIGGER limit might be exceeded.
Signed-off-by: Mathieu Othacehe <m.othacehe@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-trigger.c

@@ -254,8 +254,11 @@ static int iio_trigger_attach_poll_func(struct iio_trigger *trig,
 
 	/* Get irq number */
 	pf->irq = iio_trigger_get_irq(trig);
-	if (pf->irq < 0)
+	if (pf->irq < 0) {
+		pr_err("Could not find an available irq for trigger %s, CONFIG_IIO_CONSUMERS_PER_TRIGGER=%d limit might be exceeded\n",
+			trig->name, CONFIG_IIO_CONSUMERS_PER_TRIGGER);
 		goto out_put_module;
+	}
 
 	/* Request irq */
 	ret = request_threaded_irq(pf->irq, pf->h, pf->thread,