patch "iio: accel: bmc150: Don't make the remove function of the second" added to staging-next

This is a note to let you know that I've just added the patch titled

iio: accel: bmc150: Don't make the remove function of the second

to my staging git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-next branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release during the merge window.

If you have any questions about this process, please let me know.

From f407e2dca0f559621114eeaf657880d83f237fbd Mon Sep 17 00:00:00 2001
From: Hans de Goede <[email protected]>
Date: Sun, 23 May 2021 19:00:56 +0200
Subject: iio: accel: bmc150: Don't make the remove function of the second
accelerometer unregister itself

On machines with dual accelerometers described in a single ACPI fwnode, the bmc150_accel_probe() instantiates a second i2c-client for the second accelerometer.

A pointer to this manually instantiated second i2c-client is stored inside the iio_dev's private-data through bmc150_set_second_device(), so that the i2c-client can be unregistered from bmc150_accel_remove().

Before this commit bmc150_set_second_device() took only 1 argument so it would store the pointer in private-data of the iio_dev belonging to the manually instantiated i2c-client, leading to the bmc150_accel_remove() call for the second_dev trying to unregister *itself* while it was being removed, leading to a deadlock and rmmod hanging.

Change bmc150_set_second_device() to take 2 arguments: 1. The i2c-client which is instantiating the second i2c-client for the 2nd accelerometer and
2. The second-device pointer itself (which also is an i2c-client).

This will store the second_device pointer in the private data of the iio_dev belonging to the (ACPI instantiated) i2c-client for the first accelerometer and will make bmc150_accel_remove() unregister the second_device i2c-client when called for the first client, avoiding the deadlock.

---
 drivers/iio/accel/bmc150-accel-core.c | 4 ++--
 drivers/iio/accel/bmc150-accel-i2c.c  | 2 +-
 drivers/iio/accel/bmc150-accel.h      | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

index c526d83f14d5..1aec873bee03 100644
@@ -1811,11 +1811,11 @@ struct i2c_client *bmc150_get_second_device(struct i2c_client *client)
 }
 EXPORT_SYMBOL_GPL(bmc150_get_second_device);
 
-void bmc150_set_second_device(struct i2c_client *client)
+void bmc150_set_second_device(struct i2c_client *client, struct i2c_client *second_dev)
 {
 	struct bmc150_accel_data *data = iio_priv(i2c_get_clientdata(client));
 
-	data->second_device = client;
+	data->second_device = second_dev;
 }
 EXPORT_SYMBOL_GPL(bmc150_set_second_device);
 

index 69f709319484..2afaae0294ee 100644
@@ -70,7 +70,7 @@ static int bmc150_accel_probe(struct i2c_client *client,
 
 		second_dev = i2c_acpi_new_device(&client->dev, 1, &board_info);
 		if (!IS_ERR(second_dev))
-			bmc150_set_second_device(second_dev);
+			bmc150_set_second_device(client, second_dev);
 	}
 #endif
 

index 6024f15b9700..e30c1698f6fb 100644
@@ -18,7 +18,7 @@ int bmc150_accel_core_probe(struct device *dev, struct regmap *regmap, int irq,
 			    const char *name, bool block_supported);
 int bmc150_accel_core_remove(struct device *dev);
 struct i2c_client *bmc150_get_second_device(struct i2c_client *second_device);
-void bmc150_set_second_device(struct i2c_client *second_device);
+void bmc150_set_second_device(struct i2c_client *client, struct i2c_client *second_dev);
 extern const struct dev_pm_ops bmc150_accel_pm_ops;
 extern const struct regmap_config bmc150_regmap_conf;
 

2.32.0