linux-kernel - [PATCH v1 2/3] driver core: Update device link status properly for device_bind

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Date:   Tue,  2 Mar 2021 13:11:31 -0800
From:   Saravana Kannan <saravanak@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Saravana Kannan <saravanak@...gle.com>,
        Michael Walle <michael@...le.cc>,
        Jon Hunter <jonathanh@...dia.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Guenter Roeck <linux@...ck-us.net>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH v1 2/3] driver core: Update device link status properly for device_bind_driver()

Device link status was not getting updated correctly when
device_bind_driver() is called on a device. This causes a warning[1].
Fix this by updating device links that can be updated and dropping
device links that can't be updated to a sensible state.

[1] - https://lore.kernel.org/lkml/56f7d032-ba5a-a8c7-23de-2969d98c527e@nvidia.com/
Signed-off-by: Saravana Kannan <saravanak@...gle.com>
---
 drivers/base/base.h |  1 +
 drivers/base/core.c | 35 +++++++++++++++++++++++++++++++++++
 drivers/base/dd.c   |  4 +++-
 3 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/drivers/base/base.h b/drivers/base/base.h
index 52b3d7b75c27..1b44ed588f66 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -185,6 +185,7 @@ extern int device_links_read_lock(void);
 extern void device_links_read_unlock(int idx);
 extern int device_links_read_lock_held(void);
 extern int device_links_check_suppliers(struct device *dev);
+extern void device_links_force_bind(struct device *dev);
 extern void device_links_driver_bound(struct device *dev);
 extern void device_links_driver_cleanup(struct device *dev);
 extern void device_links_no_driver(struct device *dev);
diff --git a/drivers/base/core.c b/drivers/base/core.c
index f29839382f81..45c75cc96fdc 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1153,6 +1153,41 @@ static ssize_t waiting_for_supplier_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(waiting_for_supplier);
 
+/**
+ * device_links_force_bind - Prepares device to be force bound
+ * @dev: Consumer device.
+ *
+ * device_bind_driver() force binds a device to a driver without calling any
+ * driver probe functions. So the consumer really isn't going to wait for any
+ * supplier before it's bound to the driver. We still want the device link
+ * states to be sensible when this happens.
+ *
+ * In preparation for device_bind_driver(), this function goes through each
+ * supplier device links and checks if the supplier is bound. If it is, then
+ * the device link status is set to CONSUMER_PROBE. Otherwise, the device link
+ * is dropped. Links without the DL_FLAG_MANAGED flag set are ignored.
+ */
+void device_links_force_bind(struct device *dev)
+{
+	struct device_link *link, *ln;
+
+	device_links_write_lock();
+
+	list_for_each_entry_safe(link, ln, &dev->links.suppliers, c_node) {
+		if (!(link->flags & DL_FLAG_MANAGED))
+			continue;
+
+		if (link->status != DL_STATE_AVAILABLE) {
+			device_link_drop_managed(link);
+			continue;
+		}
+		WRITE_ONCE(link->status, DL_STATE_CONSUMER_PROBE);
+	}
+	dev->links.status = DL_DEV_PROBING;
+
+	device_links_write_unlock();
+}
+
 /**
  * device_links_driver_bound - Update device links after probing its driver.
  * @dev: Device to update the links for.
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index f18963f42e21..eb201c6d5a6a 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -460,8 +460,10 @@ int device_bind_driver(struct device *dev)
 	int ret;
 
 	ret = driver_sysfs_add(dev);
-	if (!ret)
+	if (!ret) {
+		device_links_force_bind(dev);
 		driver_bound(dev);
+	}
 	else if (dev->bus)
 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 					     BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
-- 
2.30.1.766.gb4fecdf3b7-goog