[PATCH v3 3/4] i2c: Replace list-based mechanism for handling userspace-created clients

[Heiner Kallweit <hkallweit1@gmail.com>]

Similar to the list of auto-detected clients, we can also replace the
list of userspace-created clients with flagging such client devices.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
v3:
- protect client unregistration with core_lock mutex
---
 drivers/i2c/i2c-core-base.c | 61 +++++++++++++++----------------------
 include/linux/i2c.h         |  1 +
 2 files changed, 25 insertions(+), 37 deletions(-)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 42c62839d..15397cfaa 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1293,14 +1293,12 @@ new_device_store(struct device *dev, struct device_attribute *attr,
 		info.flags |= I2C_CLIENT_SLAVE;
 	}
 
+	info.flags |= I2C_CLIENT_USER;
+
 	client = i2c_new_client_device(adap, &info);
 	if (IS_ERR(client))
 		return PTR_ERR(client);
 
-	/* Keep track of the added device */
-	mutex_lock(&adap->userspace_clients_lock);
-	list_add_tail(&client->detected, &adap->userspace_clients);
-	mutex_unlock(&adap->userspace_clients_lock);
 	dev_info(dev, "%s: Instantiated device %s at 0x%02hx\n", "new_device",
 		 info.type, info.addr);
 
@@ -1308,6 +1306,15 @@ new_device_store(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_WO(new_device);
 
+static int __i2c_find_user_addr(struct device *dev, void *addrp)
+{
+	struct i2c_client *client = i2c_verify_client(dev);
+	unsigned short addr = *(unsigned short *)addrp;
+
+	return client && client->flags & I2C_CLIENT_USER &&
+	       i2c_encode_flags_to_addr(client) == addr;
+}
+
 /*
  * And of course let the users delete the devices they instantiated, if
  * they got it wrong. This interface can only be used to delete devices
@@ -1322,7 +1329,8 @@ delete_device_store(struct device *dev, struct device_attribute *attr,
 		    const char *buf, size_t count)
 {
 	struct i2c_adapter *adap = to_i2c_adapter(dev);
-	struct i2c_client *client, *next;
+	struct i2c_client *client;
+	struct device *child_dev;
 	unsigned short addr;
 	char end;
 	int res;
@@ -1338,28 +1346,20 @@ delete_device_store(struct device *dev, struct device_attribute *attr,
 		return -EINVAL;
 	}
 
+	mutex_lock (&core_lock);
 	/* Make sure the device was added through sysfs */
-	res = -ENOENT;
-	mutex_lock_nested(&adap->userspace_clients_lock,
-			  i2c_adapter_depth(adap));
-	list_for_each_entry_safe(client, next, &adap->userspace_clients,
-				 detected) {
-		if (i2c_encode_flags_to_addr(client) == addr) {
-			dev_info(dev, "%s: Deleting device %s at 0x%02hx\n",
-				 "delete_device", client->name, client->addr);
-
-			list_del(&client->detected);
-			i2c_unregister_device(client);
-			res = count;
-			break;
-		}
+	child_dev = device_find_child(&adap->dev, &addr, __i2c_find_user_addr);
+	if (!child_dev) {
+		mutex_unlock (&core_lock);
+		dev_err(dev, "Can't find userspace-created device at %#x\n", addr);
+		return -ENOENT;
 	}
-	mutex_unlock(&adap->userspace_clients_lock);
+	client = i2c_verify_client(child_dev);
+	i2c_unregister_device(client);
+	put_device(child_dev);
+	mutex_unlock (&core_lock);
 
-	if (res < 0)
-		dev_err(dev, "%s: Can't find device in list\n",
-			"delete_device");
-	return res;
+	return count;
 }
 static DEVICE_ATTR_IGNORE_LOCKDEP(delete_device, S_IWUSR, NULL,
 				  delete_device_store);
@@ -1722,7 +1722,6 @@ static int __unregister_dummy(struct device *dev, void *dummy)
 void i2c_del_adapter(struct i2c_adapter *adap)
 {
 	struct i2c_adapter *found;
-	struct i2c_client *client, *next;
 
 	/* First make sure that this adapter was ever added */
 	mutex_lock(&core_lock);
@@ -1735,18 +1734,6 @@ void i2c_del_adapter(struct i2c_adapter *adap)
 
 	i2c_acpi_remove_space_handler(adap);
 
-	/* Remove devices instantiated from sysfs */
-	mutex_lock_nested(&adap->userspace_clients_lock,
-			  i2c_adapter_depth(adap));
-	list_for_each_entry_safe(client, next, &adap->userspace_clients,
-				 detected) {
-		dev_dbg(&adap->dev, "Removing %s at 0x%x\n", client->name,
-			client->addr);
-		list_del(&client->detected);
-		i2c_unregister_device(client);
-	}
-	mutex_unlock(&adap->userspace_clients_lock);
-
 	/* Detach any active clients. This can't fail, thus we do not
 	 * check the returned value. This is a two-pass process, because
 	 * we can't remove the dummy devices during the first pass: they
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index c4c8e841a..376136b18 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -333,6 +333,7 @@ struct i2c_client {
 #define I2C_CLIENT_HOST_NOTIFY	0x40	/* We want to use I2C host notify */
 #define I2C_CLIENT_WAKE		0x80	/* for board_info; true iff can wake */
 #define I2C_CLIENT_AUTO		0x100	/* for board_info; auto-detected */
+#define I2C_CLIENT_USER		0x200	/* for board_info; userspace-created */
 #define I2C_CLIENT_SCCB		0x9000	/* Use Omnivision SCCB protocol */
 					/* Must match I2C_M_STOP|IGNORE_NAK */
 
-- 
2.47.0