Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   alexis.lothore@bootlin.com
To:     mdf@kernel.org, hao.wu@intel.com, yilun.xu@intel.com,
        trix@redhat.com, russell.h.weight@intel.com,
        linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     thomas.petazzoni@bootlin.com, nicolas.carrier@orolia.com
Subject: [PATCH] fpga: bridge: properly initialize bridge device before populating children
Date:   Tue,  4 Apr 2023 15:31:02 +0200
Message-Id: <20230404133102.2837535-2-alexis.lothore@bootlin.com>
In-Reply-To: <20230404133102.2837535-1-alexis.lothore@bootlin.com>
References: <20230404133102.2837535-1-alexis.lothore@bootlin.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Alexis Lothoré <alexis.lothore@bootlin.com>

The current code path can lead to warnings because of uninitialized device,
which contains, as a consequence, uninitialized kobject. The uninitialized
device is passed to of_platform_populate, which will at some point, while
creating child device, try to get a reference on uninitialized parent,
resulting in the following warning:

kobject: '(null)' ((ptrval)): is not initialized, yet kobject_get() is
being called.

The warning is observed after migrating a kernel 5.10.x to 6.1.x.
Reverting commit 0d70af3c2530 ("fpga: bridge: Use standard dev_release for
class driver") seems to remove the warning.
This commit aggregates device_initialize() and device_add() into
device_register() but this new call is done AFTER of_platform_populate

Fixes: 0d70af3c2530 ("fpga: bridge: Use standard dev_release for class driver")
Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
---
 drivers/fpga/fpga-bridge.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/fpga/fpga-bridge.c b/drivers/fpga/fpga-bridge.c
index 727704431f61..13918c8c839e 100644
--- a/drivers/fpga/fpga-bridge.c
+++ b/drivers/fpga/fpga-bridge.c
@@ -360,7 +360,6 @@ fpga_bridge_register(struct device *parent, const char *name,
 	bridge->dev.parent = parent;
 	bridge->dev.of_node = parent->of_node;
 	bridge->dev.id = id;
-	of_platform_populate(bridge->dev.of_node, NULL, NULL, &bridge->dev);
 
 	ret = dev_set_name(&bridge->dev, "br%d", id);
 	if (ret)
@@ -372,6 +371,8 @@ fpga_bridge_register(struct device *parent, const char *name,
 		return ERR_PTR(ret);
 	}
 
+	of_platform_populate(bridge->dev.of_node, NULL, NULL, &bridge->dev);
+
 	return bridge;
 
 error_device:
-- 
2.40.0