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

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Date:   Fri, 9 Sep 2016 22:40:37 +0200
From:   Peter Rosin <peda@...ntia.se>
To:     <jim_baxter@...tor.com>, <linux-i2c@...r.kernel.org>
CC:     Peter Korsgaard <peter.korsgaard@...co.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 0/2] i2c: Stop i2c modules being unloaded while in use.

On 2016-09-07 22:05, jim_baxter@...tor.com wrote:
> From: Jim Baxter <jim_baxter@...tor.com>
> 
> This patchset adds a new i2c_mux_add_reparented_adapter API to the i2c
> that allows owning modules to use module_get/module_put and stop the
> i2c bus module being removed whilst in use.
> 
> This was tested on an ARM i.MX6 Sabre board with the pca953x gpio module.
> 
> Joshua Frkuska (2):
>   i2c-mux: add i2c_mux_add_reparented_adapter api
>   i2c-mux-gpio: call i2c_add_reparented_mux_adapter

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?

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?

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?

CHeers,
Peter