linux-kernel - [PATCH] mailbox: check ->last_tx_done for NULL in case of timer-based polling

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Date:   Tue, 21 Mar 2017 16:57:34 +0000
From:   Alexey Klimov <alexey.klimov@....com>
To:     jassisinghbrar@...il.com, linux-kernel@...r.kernel.org
Cc:     sudeep.holla@....com, jaswinder.singh@...aro.org
Subject: [PATCH] mailbox: check ->last_tx_done for NULL in case of timer-based polling

It is allowed by code to register mailbox controller that sets txdone_poll
flag to request timer-based polling with missed ->last_tx_done() method.
If such thing happens and since presence of last_tx_done() is not checked
it will fail in hrtimer callback function txdone_hrtimer() when first
message will be transmitted.

This patch adds check for this method and logging of error on
registration of mailbox controller if it requested timer-based polling.

Signed-off-by: Alexey Klimov <alexey.klimov@....com>
---
 drivers/mailbox/mailbox.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index 4671f8a..59b7221 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -453,6 +453,12 @@ int mbox_controller_register(struct mbox_controller *mbox)
 		txdone = TXDONE_BY_ACK;

 	if (txdone == TXDONE_BY_POLL) {
+
+		if (!mbox->ops->last_tx_done) {
+			dev_err(mbox->dev, "last_tx_done method is absent\n");
+			return -EINVAL;
+		}
+
 		hrtimer_init(&mbox->poll_hrt, CLOCK_MONOTONIC,
 			     HRTIMER_MODE_REL);
 		mbox->poll_hrt.function = txdone_hrtimer;
-- 
1.9.1