FAILED: patch "[PATCH] i2c: core: Lock address during client device instantiation" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 8d3cefaf659265aa82b0373a563fdb9d16a2b947
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024100713-creatable-lapped-c0b3@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

8d3cefaf6592 ("i2c: core: Lock address during client device instantiation")
73febd775bdb ("i2c: create debugfs entry per adapter")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8d3cefaf659265aa82b0373a563fdb9d16a2b947 Mon Sep 17 00:00:00 2001
From: Heiner Kallweit <hkallweit1@gmail.com>
Date: Thu, 15 Aug 2024 21:44:50 +0200
Subject: [PATCH] i2c: core: Lock address during client device instantiation

Krzysztof reported an issue [0] which is caused by parallel attempts to
instantiate the same I2C client device. This can happen if driver
supports auto-detection, but certain devices are also instantiated
explicitly.
The original change isn't actually wrong, it just revealed that I2C core
isn't prepared yet to handle this scenario.
Calls to i2c_new_client_device() can be nested, therefore we can't use a
simple mutex here. Parallel instantiation of devices at different addresses
is ok, so we just have to prevent parallel instantiation at the same address.
We can use a bitmap with one bit per 7-bit I2C client address, and atomic
bit operations to set/check/clear bits.
Now a parallel attempt to instantiate a device at the same address will
result in -EBUSY being returned, avoiding the "sysfs: cannot create duplicate
filename" splash.

Note: This patch version includes small cosmetic changes to the Tested-by
      version, only functional change is that address locking is supported
      for slave addresses too.

[0] https://lore.kernel.org/linux-i2c/9479fe4e-eb0c-407e-84c0-bd60c15baf74@ans.pl/T/#m12706546e8e2414d8f1a0dc61c53393f731685cc

Fixes: caba40ec3531 ("eeprom: at24: Probe for DDR3 thermal sensor in the SPD case")
Cc: stable@vger.kernel.org
Tested-by: Krzysztof Piotr Oledzki <ole@ans.pl>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index b63f75e44296..e39e8d792d03 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -915,6 +915,27 @@ int i2c_dev_irq_from_resources(const struct resource *resources,
 	return 0;
 }
 
+/*
+ * Serialize device instantiation in case it can be instantiated explicitly
+ * and by auto-detection
+ */
+static int i2c_lock_addr(struct i2c_adapter *adap, unsigned short addr,
+			 unsigned short flags)
+{
+	if (!(flags & I2C_CLIENT_TEN) &&
+	    test_and_set_bit(addr, adap->addrs_in_instantiation))
+		return -EBUSY;
+
+	return 0;
+}
+
+static void i2c_unlock_addr(struct i2c_adapter *adap, unsigned short addr,
+			    unsigned short flags)
+{
+	if (!(flags & I2C_CLIENT_TEN))
+		clear_bit(addr, adap->addrs_in_instantiation);
+}
+
 /**
  * i2c_new_client_device - instantiate an i2c device
  * @adap: the adapter managing the device
@@ -962,6 +983,10 @@ i2c_new_client_device(struct i2c_adapter *adap, struct i2c_board_info const *inf
 		goto out_err_silent;
 	}
 
+	status = i2c_lock_addr(adap, client->addr, client->flags);
+	if (status)
+		goto out_err_silent;
+
 	/* Check for address business */
 	status = i2c_check_addr_busy(adap, i2c_encode_flags_to_addr(client));
 	if (status)
@@ -993,6 +1018,8 @@ i2c_new_client_device(struct i2c_adapter *adap, struct i2c_board_info const *inf
 	dev_dbg(&adap->dev, "client [%s] registered with bus id %s\n",
 		client->name, dev_name(&client->dev));
 
+	i2c_unlock_addr(adap, client->addr, client->flags);
+
 	return client;
 
 out_remove_swnode:
@@ -1004,6 +1031,7 @@ i2c_new_client_device(struct i2c_adapter *adap, struct i2c_board_info const *inf
 	dev_err(&adap->dev,
 		"Failed to register i2c client %s at 0x%02x (%d)\n",
 		client->name, client->addr, status);
+	i2c_unlock_addr(adap, client->addr, client->flags);
 out_err_silent:
 	if (need_put)
 		put_device(&client->dev);
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 7eedd0c662da..8d79440cd8ce 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -761,6 +761,9 @@ struct i2c_adapter {
 	struct regulator *bus_regulator;
 
 	struct dentry *debugfs;
+
+	/* 7bit address space */
+	DECLARE_BITMAP(addrs_in_instantiation, 1 << 7);
 };
 #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)