linux-kernel - Re: [PATCH] i2c: dev: Fix bus callback return values

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Date:   Thu, 9 Mar 2023 22:11:24 +0100
From:   Wolfram Sang <wsa@...nel.org>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        linux-i2c@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: dev: Fix bus callback return values

On Thu, Mar 09, 2023 at 08:45:46AM +0100, Geert Uytterhoeven wrote:
> The i2cdev_{at,de}tach_adapter() callbacks are used for two purposes:
>   1. As notifier callbacks, when (un)registering I2C adapters created or
>      destroyed after i2c_dev_init(),
>   2. As bus iterator callbacks, for registering already existing
>      adapters from i2c_dev_init(), and for cleanup.
> 
> Unfortunately both use cases expect different return values: the former
> expects NOTIFY_* return codes, while the latter expects zero or error
> codes, and aborts in case of error.
> 
> Hence in case 2, as soon as i2cdev_{at,de}tach_adapter() returns
> (non-zero) NOTIFY_OK, the bus iterator aborts.  This causes (a) only the
> first already existing adapter to be registered, leading to missing
> /dev/i2c-* entries, and (b) a failure to unregister all but the first
> I2C adapter during cleanup.
> 
> Fix this by introducing separate callbacks for the bus iterator,
> wrapping the notifier functions, and always returning succes.
> Any errors inside these callback functions are unlikely to happen, and
> are fatal anyway.
> 
> Fixes: cddf70d0bce71c2a ("i2c: dev: fix notifier return values")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>

Applied to for-current, thanks!


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