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From:   Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org,
        Saravana Kannan <saravanak@google.com>,
        linux-acpi@vger.kernel.org,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Ferry Toth <fntoth@gmail.com>
Subject: [PATCH v1 2/2] device property: Don't clear secondary pointer for shared primary firmware node
Date:   Thu, 22 Oct 2020 21:41:00 +0300
Message-Id: <20201022184100.71659-2-andriy.shevchenko@linux.intel.com>
In-Reply-To: <20201022184100.71659-1-andriy.shevchenko@linux.intel.com>
References: <20201022184100.71659-1-andriy.shevchenko@linux.intel.com>
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It appears that firmware nodes can be shared between devices. In such case
when a (child) device is about to be deleted, its firmware node may be shared
and ACPI_COMPANION_SET(..., NULL) call for it breaks the secondary link
of the shared primary firmware node.

In order to prevent that, check, if the device has a parent and parent's
firmware node is shared with its child, and avoid crashing the link.

Fixes: c15e1bdda436 ("device property: Fix the secondary firmware node handling in set_primary_fwnode()")
Reported-by: Ferry Toth <fntoth@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/base/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 41feab679fa1..78114ddac755 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -4264,6 +4264,7 @@ static inline bool fwnode_is_primary(struct fwnode_handle *fwnode)
  */
 void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
 {
+	struct device *parent = dev->parent;
 	struct fwnode_handle *fn = dev->fwnode;
 
 	if (fwnode) {
@@ -4278,7 +4279,8 @@ void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
 	} else {
 		if (fwnode_is_primary(fn)) {
 			dev->fwnode = fn->secondary;
-			fn->secondary = ERR_PTR(-ENODEV);
+			if (!(parent && fn == parent->fwnode))
+				fn->secondary = ERR_PTR(-ENODEV);
 		} else {
 			dev->fwnode = NULL;
 		}
-- 
2.28.0