i2c: core: Lock address during client device instantiation

commit 8d3cefaf659265aa82b0373a563fdb9d16a2b947 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 7e7b15440832b316c0bb522638553712afb6e634..43da2c21165537196f4106a170a04de3a62efe80 100644 (file)
--- 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 @@ out_err:
        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 c11624a3d9c04a168d0d6b82c5c4f275e931b2d3..ab603b79f23fd3d97ff520cc9ae1d5b75554d6f1 100644 (file)
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -748,6 +748,9 @@ 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)