Re: [PATCH v2] i2c: core: Lock address during client device instantiation

[Wolfram Sang <wsa+renesas@sang-engineering.com>]

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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!


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