linux-kernel - [PATCH] iio: trigger: Add validation to reject devices requiring top half

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Message-ID: <20250503190044.32511-1-gye976@gmail.com>
Date: Sun,  4 May 2025 04:00:43 +0900
From: Gyeyoung Baek <gye976@...il.com>
To: Jonathan Cameron <jic23@...nel.org>,
	David Lechner <dlechner@...libre.com>,
	Nuno Sá <nuno.sa@...log.com>,
	Andy Shevchenko <andy@...nel.org>
Cc: Gyeyoung Baek <gye976@...il.com>,
	linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] iio: trigger: Add validation to reject devices requiring top half

Some device drivers implement top-half handler,
which is not compatible with threaded handler trigger.
This patch adds a validation function to reject such devices,
allowing only iio_pollfunc_store_time().

Signed-off-by: Gyeyoung Baek <gye976@...il.com>
---
 drivers/iio/trigger/iio-trig-loop.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/drivers/iio/trigger/iio-trig-loop.c b/drivers/iio/trigger/iio-trig-loop.c
index 7aaed0611899..a37615567a6c 100644
--- a/drivers/iio/trigger/iio-trig-loop.c
+++ b/drivers/iio/trigger/iio-trig-loop.c
@@ -7,18 +7,12 @@
  *
  * Note this is still rather experimental and may eat babies.
  *
- * Todo
- * * Protect against connection of devices that 'need' the top half
- *   handler.
- * * Work out how to run top half handlers in this context if it is
- *   safe to do so (timestamp grabbing for example)
- *
  * Tested against a max1363. Used about 33% cpu for the thread and 20%
  * for generic_buffer piping to /dev/null. Watermark set at 64 on a 128
  * element kfifo buffer.
  */
 
-#include <linux/kernel.h>
+#include <linux/errno.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
@@ -27,8 +21,10 @@
 #include <linux/freezer.h>
 
 #include <linux/iio/iio.h>
-#include <linux/iio/trigger.h>
 #include <linux/iio/sw_trigger.h>
+#include <linux/iio/trigger.h>
+
+#include "linux/iio/trigger_consumer.h"
 
 struct iio_loop_info {
 	struct iio_sw_trigger swt;
@@ -71,8 +67,25 @@ static int iio_loop_trigger_set_state(struct iio_trigger *trig, bool state)
 	return 0;
 }
 
+/*
+ * Protect against connection of devices that 'need' the top half
+ * handler.
+ */
+static int iio_loop_trigger_validate_device(struct iio_trigger *trig,
+						struct iio_dev *indio_dev)
+{
+	struct iio_poll_func *pf = indio_dev->pollfunc;
+
+	/* Only iio timestamp grabbing is allowed. */
+	if (pf->h && pf->h != iio_pollfunc_store_time)
+		return -EINVAL;
+
+	return 0;
+}
+
 static const struct iio_trigger_ops iio_loop_trigger_ops = {
 	.set_trigger_state = iio_loop_trigger_set_state,
+	.validate_device = iio_loop_trigger_validate_device,
 };
 
 static struct iio_sw_trigger *iio_trig_loop_probe(const char *name)
-- 
2.43.0