Re: [PATCH v1 0/2] i2c: Stop i2c modules being unloaded while in use.

From	"Baxter, Jim" <jim_baxter@mentor.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v1 0/2] i2c: Stop i2c modules being unloaded while in use.
Date	2016-09-13 19:00 +0200
Message-ID	<sgZdU-4vC-21@gated-at.bofh.it> (permalink)
References	<seRkt-4qy-3@gated-at.bofh.it> <sgZdU-4vC-23@gated-at.bofh.it>
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Hi Peter,

> nitpick: Patch subjects for the second patch is wrong.
>
> "reparented" is a bit dual when dealing with i2c adapter trees.
> i2c_mux_add_owned_adapter is perhaps clearer?

Agreed, I will update that.

>
>
> Aside from that, I'm not using modules much and need some enlightenment
> as to why the i2c_del_mux_adapter() call in i2c_mux_gpio_remove() is not
> sufficient and what exactly the problem is? Why would someone/something
> unload the i2c-mux module prematurely?

It is not a normal operation to remove the i2c gpio mux, however systemd
could unload modules out of order if users are restarting services
incorrectly and cause unintended side-effects. This change would stop an
i2c-mux that maybe controlling a voltage regulator from being unloaded
and disabling power to parts of the system unexpectedly.

>
>
> Would it be an alternative to make i2c-mux a proper kernel object of
> some kind? I mean, why do not all other mux users also need to modify
> the owner? Why is i2c-mux-gpio special?
>

i2c-mux-gpio is not special, the code inserted by
[PATCH v1 1/2] i2c-mux: add i2c_mux_add_reparented_adapter api could be
used by other muxes if required.

Best regards
Jim

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Re: [PATCH v1 0/2] i2c: Stop i2c modules being unloaded while in use. "Baxter, Jim" <jim_baxter@mentor.com> - 2016-09-13 19:00 +0200

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