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, but no functional change.
[0] https://lore.kernel.org/linux-i2c/9479fe4e-eb0c-407e-84c0-bd60c15baf74@xxxxxx/T/#m12706546e8e2414d8f1a0dc61c53393f731685cc
Fixes: caba40ec3531 ("eeprom: at24: Probe for DDR3 thermal sensor in the SPD case")
Cc: stable@xxxxxxxxxxxxxxx
Tested-by: Krzysztof Piotr Oledzki <ole@xxxxxx>
Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
---
drivers/i2c/i2c-core-base.c | 28 ++++++++++++++++++++++++++++
include/linux/i2c.h | 3 +++
2 files changed, 31 insertions(+)
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index b63f75e44..39892b6f8 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) && !(flags & I2C_CLIENT_SLAVE) &&
+ 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) && !(flags & I2C_CLIENT_SLAVE))
+ 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 07e33bbc9..e555d0cf8 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)
--
2.46.0
