Driver core fixes for 7.1-rc1

- Prevent a device from being probed before device_add() has finished
   initializing it; gate probe with a "ready_to_probe" device flag to
   avoid races with concurrent driver_register() calls
 
 - Fix a kernel-doc warning for DEV_FLAG_COUNT introduced by the above
 
 - Return -ENOTCONN from software_node_get_reference_args() when a
   referenced software node is known but not yet registered, allowing
   callers to defer probe
 
 - In sysfs_group_attrs_change_owner(), also check is_visible_const();
   missed when the const variant was introduced
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Merge tag 'driver-core-7.1-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core

Pull driver core fixes from Danilo Krummrich:

 - Prevent a device from being probed before device_add() has finished
   initializing it; gate probe with a "ready_to_probe" device flag to
   avoid races with concurrent driver_register() calls

 - Fix a kernel-doc warning for DEV_FLAG_COUNT introduced by the above

 - Return -ENOTCONN from software_node_get_reference_args() when a
   referenced software node is known but not yet registered, allowing
   callers to defer probe

 - In sysfs_group_attrs_change_owner(), also check is_visible_const();
   missed when the const variant was introduced

* tag 'driver-core-7.1-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core:
  driver core: Add kernel-doc for DEV_FLAG_COUNT enum value
  sysfs: attribute_group: Respect is_visible_const() when changing owner
  software node: return -ENOTCONN when referenced swnode is not registered yet
  driver core: Don't let a device probe until it's ready

drivers/base/core.c

@@ -3688,6 +3688,21 @@ int device_add(struct device *dev)
 		fw_devlink_link_device(dev);
 	}
 
+	/*
+	 * The moment the device was linked into the bus's "klist_devices" in
+	 * bus_add_device() then it's possible that probe could have been
+	 * attempted in a different thread via userspace loading a driver
+	 * matching the device. "ready_to_probe" being unset would have
+	 * blocked those attempts. Now that all of the above initialization has
+	 * happened, unblock probe. If probe happens through another thread
+	 * after this point but before bus_probe_device() runs then it's fine.
+	 * bus_probe_device() -> device_initial_probe() -> __device_attach()
+	 * will notice (under device_lock) that the device is already bound.
+	 */
+	device_lock(dev);
+	dev_set_ready_to_probe(dev);
+	device_unlock(dev);
+
 	bus_probe_device(dev);
 
 	/*

drivers/base/dd.c

@@ -836,6 +836,26 @@ static int __driver_probe_device(const struct device_driver *drv, struct device
 	if (dev->driver)
 		return -EBUSY;
 
+	/*
+	 * In device_add(), the "struct device" gets linked into the subsystem's
+	 * list of devices and broadcast to userspace (via uevent) before we're
+	 * quite ready to probe. Those open pathways to driver probe before
+	 * we've finished enough of device_add() to reliably support probe.
+	 * Detect this and tell other pathways to try again later. device_add()
+	 * itself will also try to probe immediately after setting
+	 * "ready_to_probe".
+	 */
+	if (!dev_ready_to_probe(dev))
+		return dev_err_probe(dev, -EPROBE_DEFER, "Device not ready to probe\n");
+
+	/*
+	 * Set can_match = true after calling dev_ready_to_probe(), so
+	 * driver_deferred_probe_add() won't actually add the device to the
+	 * deferred probe list when dev_ready_to_probe() returns false.
+	 *
+	 * When dev_ready_to_probe() returns false, it means that device_add()
+	 * will do another probe() attempt for us.
+	 */
 	dev->can_match = true;
 	dev_dbg(dev, "bus: '%s': %s: matched device with driver %s\n",
 		drv->bus->name, __func__, drv->name);

drivers/base/property.c

@@ -602,6 +602,8 @@ EXPORT_SYMBOL_GPL(fwnode_property_match_property_string);
  *	    %-ENOENT when the index is out of bounds, the index has an empty
  *		     reference or the property was not found
  *	    %-EINVAL on parse error
+ *	    %-ENOTCONN when the remote firmware node exists but has not been
+ *		       registered yet
  */
 int fwnode_property_get_reference_args(const struct fwnode_handle *fwnode,
 				       const char *prop, const char *nargs_prop,

drivers/base/swnode.c

@@ -554,7 +554,7 @@ software_node_get_reference_args(const struct fwnode_handle *fwnode,
 		return -EINVAL;
 
 	if (!refnode)
-		return -ENOENT;
+		return -ENOTCONN;
 
 	if (nargs_prop) {
 		error = fwnode_property_read_u32(refnode, nargs_prop, &nargs_prop_val);

fs/sysfs/group.c

@@ -517,8 +517,11 @@ static int sysfs_group_attrs_change_owner(struct kobject *kobj,
 		struct attribute *const *attr;
 
 		for (i = 0, attr = grp->attrs; *attr; i++, attr++) {
-			if (grp->is_visible) {
-				mode = grp->is_visible(kobj, *attr, i);
+			if (grp->is_visible || grp->is_visible_const) {
+				if (grp->is_visible)
+					mode = grp->is_visible(kobj, *attr, i);
+				else
+					mode = grp->is_visible_const(kobj, *attr, i);
 				if (mode & SYSFS_GROUP_INVISIBLE)
 					break;
 				if (!mode)

include/linux/device.h

@@ -504,6 +504,22 @@ struct device_physical_location {
 	bool lid;
 };
 
+/**
+ * enum struct_device_flags - Flags in struct device
+ *
+ * Each flag should have a set of accessor functions created via
+ * __create_dev_flag_accessors() for each access.
+ *
+ * @DEV_FLAG_READY_TO_PROBE: If set then device_add() has finished enough
+ *		initialization that probe could be called.
+ * @DEV_FLAG_COUNT: Number of defined struct_device_flags.
+ */
+enum struct_device_flags {
+	DEV_FLAG_READY_TO_PROBE = 0,
+
+	DEV_FLAG_COUNT
+};
+
 /**
  * struct device - The basic device structure
  * @parent:	The device's "parent" device, the device to which it is attached.
@@ -599,6 +615,7 @@ struct device_physical_location {
  * @dma_skip_sync: DMA sync operations can be skipped for coherent buffers.
  * @dma_iommu: Device is using default IOMMU implementation for DMA and
  *		doesn't rely on dma_ops structure.
+ * @flags:	DEV_FLAG_XXX flags. Use atomic bitfield operations to modify.
  *
  * At the lowest level, every device in a Linux system is represented by an
  * instance of struct device. The device structure contains the information
@@ -721,8 +738,36 @@ struct device {
 #ifdef CONFIG_IOMMU_DMA
 	bool			dma_iommu:1;
 #endif
+
+	DECLARE_BITMAP(flags, DEV_FLAG_COUNT);
 };
 
+#define __create_dev_flag_accessors(accessor_name, flag_name) \
+static inline bool dev_##accessor_name(const struct device *dev) \
+{ \
+	return test_bit(flag_name, dev->flags); \
+} \
+static inline void dev_set_##accessor_name(struct device *dev) \
+{ \
+	set_bit(flag_name, dev->flags); \
+} \
+static inline void dev_clear_##accessor_name(struct device *dev) \
+{ \
+	clear_bit(flag_name, dev->flags); \
+} \
+static inline void dev_assign_##accessor_name(struct device *dev, bool value) \
+{ \
+	assign_bit(flag_name, dev->flags, value); \
+} \
+static inline bool dev_test_and_set_##accessor_name(struct device *dev) \
+{ \
+	return test_and_set_bit(flag_name, dev->flags); \
+}
+
+__create_dev_flag_accessors(ready_to_probe, DEV_FLAG_READY_TO_PROBE);
+
+#undef __create_dev_flag_accessors
+
 /**
  * struct device_link - Device link representation.
  * @supplier: The device on the supplier end of the link.