linux-kernel - [PATCH 2/2] extcon: Fix extcon_cable_get_state() from getting old state after notification

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Date:	Mon, 6 Jul 2015 17:46:58 +0300
From:	Roger Quadros <rogerq@...com>
To:	<cw00.choi@...sung.com>
CC:	<linux-omap@...r.kernel.org>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Roger Quadros <rogerq@...com>
Subject: [PATCH 2/2] extcon: Fix extcon_cable_get_state() from getting old state after notification

Currently the extcon code notifiers the interested listeners
before it updates the extcon state with the new state.
This will cause the listeners that use extcon_cable_get_state()
to get the stale state and loose the new state.

Fix this by first changing the extcon state variable and then
notifying listeners.

Signed-off-by: Roger Quadros <rogerq@...com>
---
 drivers/extcon/extcon.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c
index 868c6e2..26d1e1e 100644
--- a/drivers/extcon/extcon.c
+++ b/drivers/extcon/extcon.c
@@ -275,19 +275,25 @@ int extcon_update_state(struct extcon_dev *edev, u32 mask, u32 state)
 	spin_lock_irqsave(&edev->lock, flags);
 
 	if (edev->state != ((edev->state & ~mask) | (state & mask))) {
+		u32 old_state;
+
 		if (check_mutually_exclusive(edev, (edev->state & ~mask) |
 						   (state & mask))) {
 			spin_unlock_irqrestore(&edev->lock, flags);
 			return -EPERM;
 		}
 
+		old_state = edev->state;
+		edev->state &= ~mask;
+		edev->state |= state & mask;
+
 		for (index = 0; index < edev->max_supported; index++) {
-			if (is_extcon_changed(edev->state, state, index, &attached))
-				raw_notifier_call_chain(&edev->nh[index], attached, edev);
+			if (is_extcon_changed(old_state, edev->state, index,
+					      &attached))
+				raw_notifier_call_chain(&edev->nh[index],
+							attached, edev);
 		}
 
-		edev->state &= ~mask;
-		edev->state |= state & mask;
 
 		/* This could be in interrupt handler */
 		prop_buf = (char *)get_zeroed_page(GFP_ATOMIC);
-- 
2.1.4

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