linux-kernel - [PATCH] counter: microchip-tcb-capture: Add watch validation support

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Message-ID: <20250515-counter-tcb-v1-1-e547061ed80f@microchip.com>
Date: Thu, 15 May 2025 10:28:25 +0530
From: Dharma Balasubiramani <dharma.b@...rochip.com>
To: Kamel Bouhara <kamel.bouhara@...tlin.com>, William Breathitt Gray
	<wbg@...nel.org>
CC: <linux-arm-kernel@...ts.infradead.org>, <linux-iio@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Dharma Balasubiramani
	<dharma.b@...rochip.com>
Subject: [PATCH] counter: microchip-tcb-capture: Add watch validation
 support

Introduce a watch validation callback to restrict supported event and
channel combinations. This allows userspace to receive notifications only
for valid event types and sources. Specifically, enable the following
supported events on channels RA, RB, and RC:

  - COUNTER_EVENT_CAPTURE
  - COUNTER_EVENT_CHANGE_OF_STATE
  - COUNTER_EVENT_OVERFLOW
  - COUNTER_EVENT_THRESHOLD

Signed-off-by: Dharma Balasubiramani <dharma.b@...rochip.com>
---
 drivers/counter/microchip-tcb-capture.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/drivers/counter/microchip-tcb-capture.c b/drivers/counter/microchip-tcb-capture.c
index 1de3c50b9804..179ff5595143 100644
--- a/drivers/counter/microchip-tcb-capture.c
+++ b/drivers/counter/microchip-tcb-capture.c
@@ -337,6 +337,27 @@ static struct counter_comp mchp_tc_count_ext[] = {
 	COUNTER_COMP_COMPARE(mchp_tc_count_compare_read, mchp_tc_count_compare_write),
 };
 
+static int mchp_tc_watch_validate(struct counter_device *counter,
+				  const struct counter_watch *watch)
+{
+	switch (watch->channel) {
+	case COUNTER_MCHP_EVCHN_RA:
+	case COUNTER_MCHP_EVCHN_RB:
+	case COUNTER_MCHP_EVCHN_RC:
+		switch (watch->event) {
+		case COUNTER_EVENT_CAPTURE:
+		case COUNTER_EVENT_CHANGE_OF_STATE:
+		case COUNTER_EVENT_OVERFLOW:
+		case COUNTER_EVENT_THRESHOLD:
+			return 0;
+		default:
+			return -EINVAL;
+		}
+	default:
+		return -EINVAL;
+	}
+}
+
 static struct counter_count mchp_tc_counts[] = {
 	{
 		.id = 0,
@@ -351,12 +372,13 @@ static struct counter_count mchp_tc_counts[] = {
 };
 
 static const struct counter_ops mchp_tc_ops = {
-	.signal_read    = mchp_tc_count_signal_read,
+	.action_read    = mchp_tc_count_action_read,
+	.action_write   = mchp_tc_count_action_write,
 	.count_read     = mchp_tc_count_read,
 	.function_read  = mchp_tc_count_function_read,
 	.function_write = mchp_tc_count_function_write,
-	.action_read    = mchp_tc_count_action_read,
-	.action_write   = mchp_tc_count_action_write
+	.signal_read    = mchp_tc_count_signal_read,
+	.watch_validate = mchp_tc_watch_validate,
 };
 
 static const struct atmel_tcb_config tcb_rm9200_config = {

---
base-commit: 9f35e33144ae5377d6a8de86dd3bd4d995c6ac65
change-id: 20250515-counter-tcb-b6ae1945210b

Best regards,
-- 
Dharma Balasubiramani <dharma.b@...rochip.com>