| Message ID | 32a2d535-d7c8-47da-a42f-b41d3fae972f@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] i2c: core: Lock address during client device instantiation | expand |
Hi Heiner, On Thu, Aug 15, 2024 at 09:44:50PM +0200, Heiner Kallweit wrote: > > +/* > + * 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; Why don't you add a list of client devices to the adapter structure instead of using bitmap? Then you could handle cases with 10 bit addresses as well. I know that there is already a list of children in the driver core, but it is populated too late for what we need. Thanks.
On Thu, Aug 15, 2024 at 09:44:50PM +0200, Heiner Kallweit wrote: > 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> Applied to for-next, thanks!
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c index b63f75e44..e39e8d792 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 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)
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> --- v2: - fixed comment style - use address locking for slave addresses too --- drivers/i2c/i2c-core-base.c | 28 ++++++++++++++++++++++++++++ include/linux/i2c.h | 3 +++ 2 files changed, 31 insertions(+)