6.6-stable review patch. If anyone has any objections, please let me know.
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From: Heiner Kallweit hkallweit1@gmail.com
[ Upstream commit 8d3cefaf659265aa82b0373a563fdb9d16a2b947 ]
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.p...
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: Sasha Levin sashal@kernel.org --- 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 9d918a7dfddae..943f0021d6a2c 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 033de64d09bba..a3166100f0cce 100644 --- 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)