[PATCH] base/platform: fix panic when probe function is NULL

[martin . wilck]

From: Martin Wilck <Martin.Wilck@xxxxxxxxxxxxxx>

Since b8b2c7d845d5, platform_drv_probe() is called for all platform
devices. If drv->probe is NULL, and dev_pm_domain_attach() fails,
platform_drv_probe() will return the error code from dev_pm_domain_attach().

This causes real_probe() to enter the "probe_failed" path and set
dev->driver to NULL. Before b8b2c7d845d5, real_probe() would assume
success if both dev->bus->probe and drv->probe are missing.

This may cause a panic later. For example, inserting the tpm_tis
driver with parameter "force=1" (i.e. registering tpm_tis as a platform
driver) will panic in tpmm_chip_alloc() because dev->driver is NULL:

     chip->cdev.owner = chip->pdev->driver->owner;

This patch fixes this by returning success in platform_drv_probe() if
"just" dev_pm_domain_attach() had failed. This restores the semantics
of platform_device_register_XXX() if the associated platform driver has
no "probe" function.

Fixes: b8b2c7d845d5 ("base/platform: assert that dev_pm_domain
callbacks are called unconditionally")

Signed-off-by: Martin Wilck <Martin.Wilck@xxxxxxxxxxxxxx>
---
 drivers/base/platform.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 1dd6d3b..c994e76 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -513,10 +513,14 @@ static int platform_drv_probe(struct device *_dev)
 		return ret;
 
 	ret = dev_pm_domain_attach(_dev, true);
-	if (ret != -EPROBE_DEFER && drv->probe) {
-		ret = drv->probe(dev);
-		if (ret)
-			dev_pm_domain_detach(_dev, true);
+	if (ret != -EPROBE_DEFER) {
+		if (drv->probe) {
+			ret = drv->probe(dev);
+			if (ret)
+				dev_pm_domain_detach(_dev, true);
+		} else
+			/* don't fail if just dev_pm_domain_attach failed */
+			ret = 0;
 	}
 
 	if (drv->prevent_deferred_probe && ret == -EPROBE_DEFER) {
-- 
1.8.3.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/