iio: Fix error handling in iio_trigger_attach_poll_func

commit 99543823 upstream.

When attaching a pollfunc iio_trigger_attach_poll_func will allocate a
virtual irq and call the driver's set_trigger_state function. Fix error
handling to undo previous steps if any fails.

In particular this fixes handling errors from a driver's
set_trigger_state function. When using triggered buffers a failure to
enable the trigger used to make the buffer unusable.
Signed-off-by: Crestez Dan Leonard <leonard.crestez@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/staging/iio/industrialio-trigger.c

@@ -218,22 +218,35 @@ static int iio_trigger_attach_poll_func(struct iio_trigger *trig,
 
 	/* Prevent the module being removed whilst attached to a trigger */
 	__module_get(pf->indio_dev->info->driver_module);
+
+	/* Get irq number */
 	pf->irq = iio_trigger_get_irq(trig);
+	if (pf->irq < 0)
+		goto out_put_module;
+
+	/* Request irq */
 	ret = request_threaded_irq(pf->irq, pf->h, pf->thread,
 				   pf->type, pf->name,
 				   pf);
-	if (ret < 0) {
-		module_put(pf->indio_dev->info->driver_module);
-		return ret;
-	}
+	if (ret < 0)
+		goto out_put_irq;
 
+	/* Enable trigger in driver */
 	if (trig->ops && trig->ops->set_trigger_state && notinuse) {
 		ret = trig->ops->set_trigger_state(trig, true);
 		if (ret < 0)
-			module_put(pf->indio_dev->info->driver_module);
+			goto out_free_irq;
 	}
 
 	return ret;
+
+out_free_irq:
+	free_irq(pf->irq, pf);
+out_put_irq:
+	iio_trigger_put_irq(trig, pf->irq);
+out_put_module:
+	module_put(pf->indio_dev->info->driver_module);
+	return ret;
 }
 
 static int iio_trigger_dettach_poll_func(struct iio_trigger *trig,