linux-kernel - [PATCH 2/3] driver core: bus: Give error prompt for storing bus attribute drivers

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Message-Id: <20240904-bus_match_unlikely-v1-2-122318285261@quicinc.com>
Date: Wed, 04 Sep 2024 20:56:43 +0800
From: Zijun Hu <zijun_hu@...oud.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Zijun Hu <zijun_hu@...oud.com>, linux-kernel@...r.kernel.org, 
 Zijun Hu <quic_zijuhu@...cinc.com>
Subject: [PATCH 2/3] driver core: bus: Give error prompt for storing bus
 attribute drivers_probe failure

From: Zijun Hu <quic_zijuhu@...cinc.com>

drivers_probe_store() regards bus_rescan_devices_helper()'s returned
value 0 as success when scan drivers for a single device user specify
that is wrong since the following 3 failed cases also return 0:

(1) the device is dead
(2) bus has no driver which match() the device
(3) bus fails to probe() the device with any its driver

Solved by giving error prompt via dev_err() for above failed cases.

Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
---
 drivers/base/bus.c | 33 ++++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index abf090ace833..6b5ea82a44c1 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -40,6 +40,24 @@ static struct kset *bus_kset;
 	struct driver_attribute driver_attr_##_name =		\
 		__ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store)
 
+/*
+ *  Bus scans drivers for a single device, and derives from
+ *  bus_rescan_devices_helper(), but returns scanning result
+ *  as precise as possible.
+ */
+static int __must_check bus_rescan_single_device(struct device *dev)
+{
+	int ret;
+
+	if (dev->parent && dev->bus->need_parent_lock)
+		device_lock(dev->parent);
+	ret = device_attach(dev);
+	if (dev->parent && dev->bus->need_parent_lock)
+		device_unlock(dev->parent);
+
+	return ret;
+}
+
 static int __must_check bus_rescan_devices_helper(struct device *dev,
 						void *data);
 
@@ -311,12 +329,25 @@ static ssize_t drivers_probe_store(const struct bus_type *bus,
 {
 	struct device *dev;
 	int err = -EINVAL;
+	int res;
 
 	dev = bus_find_device_by_name(bus, NULL, buf);
 	if (!dev)
 		return -ENODEV;
-	if (bus_rescan_devices_helper(dev, NULL) == 0)
+
+	res = bus_rescan_single_device(dev);
+	if (res < 0) {
+		/* Propagate error code upwards as precise as possible */
+		err = res;
+	} else if (res > 0) {
 		err = count;
+	} else {
+		/* Which error code to return for this case ? */
+		dev_err(dev, "device '%s' fails to attach a driver\n",
+			dev_name(dev));
+		err = count;
+	}
+
 	put_device(dev);
 	return err;
 }

-- 
2.34.1