linux-kernel - [PATCH] PCI: warn on driver probe return value greater than zero

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Message-ID: <20131101193455.18686.92302.stgit@beardog.cce.hp.com>
Date:	Fri, 01 Nov 2013 14:34:55 -0500
From:	"Stephen M. Cameron" <scameron@...rdog.cce.hp.com>
To:	bhelgaas@...gle.com
Cc:	axboe@...nel.dk, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, stephenmcameron@...il.com,
	thenzl@...hat.com, akpm@...ux-foundation.org
Subject: [PATCH] PCI: warn on driver probe return value greater than zero

From: Stephen M. Cameron <scameron@...rdog.cce.hp.com>

Ages ago, drivers could return values greater than zero from
their probe function and this would be regarded as success.
Commit f3ec4f87d607f40497 "PCI: change device runtime PM
settings for probe and remove" slightly altered this in 2010,
and commit 967577b062417b4e4b8e27b "PCI/PM: Keep runtime PM
enabled for unbound PCI devices" in late 2012 altered it more
signficantly, setting pci_dev->driver to NULL if the driver's
probe function returned a value greater than zero, which would
for example prevent the driver's remove function from being
called on rmmod.

Neither of those changes would necessarily make the driver fail
in an obvious way though, and so at least a couple drivers (cciss,
hpsa) fell into this hole since they were returning 1, and this
situation went unnoticed for quite some time.

If a driver's probe function returns a value greater than zero,
issue a warning, but otherwise treat this as success.

Signed-off-by: Stephen M. Cameron <scameron@...rdog.cce.hp.com>
---
 drivers/pci/pci-driver.c |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 98f7b9b..7fbe343 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -264,11 +264,19 @@ static long local_pci_probe(void *_ddi)
 	pm_runtime_get_sync(dev);
 	pci_dev->driver = pci_drv;
 	rc = pci_drv->probe(pci_dev, ddi->id);
-	if (rc) {
+	if (!rc)
+		return rc;
+	if (rc < 0) {
 		pci_dev->driver = NULL;
 		pm_runtime_put_sync(dev);
+		return rc;
 	}
-	return rc;
+	/*
+	 * Probe function should return < 0 for failure, 0 for success
+	 * Treat values > 0 as success, but warn.
+	 */
+	dev_warn(dev, "Driver probe function unexpectedly returned %d\n", rc);
+	return 0;
 }

 static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,

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