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From:   "Wang, Alan 1. (NSB - CN/Hangzhou)" <alan.1.wang@nokia-sbell.com>
To:     Wolfram Sang <wsa@the-dreams.de>
CC:     "linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] i2c: core: decrease reference count of device node in
 i2c_unregister_device
Thread-Topic: [PATCH] i2c: core: decrease reference count of device node in
 i2c_unregister_device
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Date:   Wed, 29 Nov 2017 08:06:01 +0000
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Hi Wolfram,

In my understand, the of_node_put(bus) is to of_get_child_by_name((adap->de=
v.of_node, "i2c-bus") or of_node_get(adap->dev.of_node).

What I said is the children of "bus" increased by "info.of_node =3D of_node=
_get(node)" in function of_i2c_register_device.

My description in last mail maybe not properly, I think all the nodes acces=
sed by of_i2c_register_device shall not be decreased, not only the dynamica=
lly added ones.=20

In my case, the SFP devices as i2c clients on one board are connected to th=
e bus through i2c mux.
When plugin the board, all the related nodes are dynamically allocated and =
added into the device tree.
Then the probe function calls of_i2c_register_devices, in which the referen=
ce count increased by " info.of_node =3D of_node_get(node)".
When plug out the board, because the reference count of those nodes are not=
 decreased down to 0, the memory of the nodes and their properties are not =
released.
New memory will be allocated but not released in the next plugin and plug o=
ut looping test.=20

Best Regards,
Lixin Wang

> -----Original Message-----
> From: Wolfram Sang [mailto:wsa@the-dreams.de]
> Sent: Tuesday, November 28, 2017 2:22 AM
> To: Wang, Alan 1. (NSB - CN/Hangzhou) <alan.1.wang@nokia-sbell.com>
> Cc: linux-i2c@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH] i2c: core: decrease reference count of device node i=
n
> i2c_unregister_device
>=20
> On Mon, Nov 27, 2017 at 03:06:55PM +0800, Lixin Wang wrote:
> > Reference count of device node was increased in
> > of_i2c_register_device, but without decreasing it in i2c_unregister_dev=
ice.
>=20
> Huh, there is an of_node_put(bus) in of_i2c_register_device?
>=20
> > Then the dynamically
> > added device node will never be released.
>=20
> Strange. Can you provide your test case, please?


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