driver core: Make state_synced device attribute writeable

If the file is written to and sync_state() hasn't been called for the
device yet, then call sync_state() for the device independent of the
state of its consumers.

This is useful for supplier devices that have one or more consumers that
don't have a driver but the consumers are in a state that don't use the
resources supplied by the supplier device.

This gives finer grained control than using the
fw_devlink.sync_state=timeout kernel commandline parameter.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20230304005355.746421-3-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-devices-state_synced

@@ -21,4 +21,9 @@ Description:
 		at the time the kernel starts are not affected or limited in
 		any way by sync_state() callbacks.
 
+		Writing "1" to this file will force a call to the device's
+		sync_state() function if it hasn't been called already. The
+		sync_state() call happens independent of the state of the
+		consumer devices.
+
 

drivers/base/base.h

@@ -164,6 +164,14 @@ static inline int driver_match_device(struct device_driver *drv,
 	return drv->bus->match ? drv->bus->match(dev, drv) : 1;
 }
 
+static inline void dev_sync_state(struct device *dev)
+{
+	if (dev->bus->sync_state)
+		dev->bus->sync_state(dev);
+	else if (dev->driver && dev->driver->sync_state)
+		dev->driver->sync_state(dev);
+}
+
 extern int driver_add_groups(struct device_driver *drv,
 			     const struct attribute_group **groups);
 extern void driver_remove_groups(struct device_driver *drv,

drivers/base/core.c

@@ -1160,10 +1160,7 @@ static void device_links_flush_sync_list(struct list_head *list,
 		if (dev != dont_lock_dev)
 			device_lock(dev);
 
-		if (dev->bus->sync_state)
-			dev->bus->sync_state(dev);
-		else if (dev->driver && dev->driver->sync_state)
-			dev->driver->sync_state(dev);
+		dev_sync_state(dev);
 
 		if (dev != dont_lock_dev)
 			device_unlock(dev);

drivers/base/dd.c

@@ -510,6 +510,27 @@ EXPORT_SYMBOL_GPL(device_bind_driver);
 static atomic_t probe_count = ATOMIC_INIT(0);
 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 
+static ssize_t state_synced_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	int ret = 0;
+
+	if (strcmp("1", buf))
+		return -EINVAL;
+
+	device_lock(dev);
+	if (!dev->state_synced) {
+		dev->state_synced = true;
+		dev_sync_state(dev);
+	} else {
+		ret = -EINVAL;
+	}
+	device_unlock(dev);
+
+	return ret ? ret : count;
+}
+
 static ssize_t state_synced_show(struct device *dev,
 				 struct device_attribute *attr, char *buf)
 {
@@ -521,7 +542,7 @@ static ssize_t state_synced_show(struct device *dev,
 
 	return sysfs_emit(buf, "%u\n", val);
 }
-static DEVICE_ATTR_RO(state_synced);
+static DEVICE_ATTR_RW(state_synced);
 
 static void device_unbind_cleanup(struct device *dev)
 {