Re: [PATCH] [RFC] i2c: Don't wait for device release in i2c_del_adapter

[Jean Delvare <jdelvare-l3A5Bk7waGM@public.gmane.org>]

On Wed, 14 Jan 2015 15:54:52 +0200, Pantelis Antoniou wrote:
> On Jan 14, 2015, at 15:49 , Jean Delvare <jdelvare-l3A5Bk7waGM@public.gmane.org> wrote:
> > That being said, nobody complained about this in 11 years, so I would
> > be surprised if it was plain wrong. I'd rather question the test code.
> > Where is it?
> 
> No-one has apparently tested removing an i2c mux device on a running system
> before.

I did that. On my system the i2c-i801 driver instantiates an
i2c-mux-gpio device. Unloading the i2c-i801 driver removes that device
and it works fine. Note however that I am not able to unload module
i2c-i801 immediately, I have to unload module i2c-mux-gpio first, as
the latter holds a reference to the former. This is because
i2c-mux-gpio calls i2c_get_adapter() on the parent I2C bus segment at
probing time.

I see that i2c-mux-pinctrl does the same, but i2c-mux-pca954x and
i2c-mux-pca9541 do not. This might be an issue. I doubt this is related
to your problem though, as these are module references and not device
references.

Were you able to figure out who is holding a reference to your
i2c_adapter? This would help us understand who is doing something wrong
here, i2c-core or your test code.

-- 
Jean Delvare
SUSE L3 Support