Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.31 as permitted sender) client-ip=23.128.96.31;
Message-ID: <3f702187-8abe-b877-80d0-db95a6ec55da@axentia.se>
Date:   Thu, 19 Oct 2023 11:26:14 +0200
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Thunderbird/102.6.0
Subject: Re: [PATCH 2/3] i2c: muxes: i2c-demux-pinctrl: Use
 of_get_i2c_adapter_by_node()
Content-Language: sv-SE
To:     Herve Codina <herve.codina@bootlin.com>,
        Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc:     linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
        Allan Nielsen <allan.nielsen@microchip.com>,
        Horatiu Vultur <horatiu.vultur@microchip.com>,
        Steen Hegelund <steen.hegelund@microchip.com>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>
References: <20231019073533.386563-1-herve.codina@bootlin.com>
 <20231019073533.386563-3-herve.codina@bootlin.com>
From:   Peter Rosin <peda@axentia.se>
In-Reply-To: <20231019073533.386563-3-herve.codina@bootlin.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?WUU0a0ljaDZNTjZVZmFsRmxNaEdScjk4OWpOM0JzSjB3UjRaSUp0NDBIeis4?=
 =?utf-8?B?QXZHZ28rTHg4U1BtekUzeS83QTNUZC8xOVIyN1d6ZXVaMXNydGhlM1NQQ09E?=
 =?utf-8?B?eWVrV1QvTU01WnVJd1hmZkYzS0VMKzlqTWFlSFV6UEs4YmdRQjRMdk5qeWMx?=
 =?utf-8?B?MGQvaDFSYm5Vbm40WVdqdEZLeGJTTzBMZ3BzV0wvNE8wWElFbFZYMFNUVldt?=
 =?utf-8?B?ZEttRUZPNEVkLzFUaGhCY3M4NkczSExhUm4vNDlLb1VmWElCdE1iMVBnY1BV?=
 =?utf-8?B?WEVXYythK2dMaEllSkprMGs5Y3ovT0llQUpRNEVuQ09QVDU0SENmOUV0bWJ3?=
 =?utf-8?B?YnY4WWZrMzlSemJ4bVFoUDV0a09xTGVvRXVJcTNZM000V1FncGdpKytlbElu?=
 =?utf-8?B?a3JsSW1VRHNYcHdtTVdpR25BM2JhWkZCUlQ5WHQ0L1pKbE9jSGxCOG01QlNW?=
 =?utf-8?B?WWlsTHptdEg0VnNwai81QnRmYUJ0VVRCck1sL0NIL2xxQTdnd3hHN2RDTXJo?=
 =?utf-8?B?SlFzODkvVXJOYVNEeHZLR2lLYzlWTHJjNTNpZmxiMCtXb2ljbzYxdHNkMmNL?=
 =?utf-8?B?OVF6QkdXNEs0djcyNUNIcXZ1bTg5di9UNHBSREpCbFpsc1FKTFNCVlVyQk10?=
 =?utf-8?B?dG5wbUQ3QjgwR3g2MjhxNklGTVoxZWZRSzdBdDhDWmtjQjhzdzFUM1V5Rmc0?=
 =?utf-8?B?Ui9XREhxMXJzQ280djZPQVJUS1E5UE5xV0pJZzhEOHNzTEhXaFF5dUI0OGxP?=
 =?utf-8?B?YTZrdVpGOVIybjJ5OElsbktsMzd0SHREREtIbk4wUnNneUxRUEI5V0V3ZHpj?=
 =?utf-8?B?UWhlYkRaSkxjeFg3RXBwVG5JQmMwbDZyQWllY2tyTzZkaUx6RXJzRk1vbVZY?=
 =?utf-8?B?U0RseGdiQWowelg2YzBTc2p2OFhlYlUxRzJYODh4UHFyaDB5V01uUEpoRDM1?=
 =?utf-8?B?T3pyQWF2WTlkSkFvbjh1SmZlSHpFaXp5eVMrSm4wWnQxUDRYN1JxT0tab0My?=
 =?utf-8?B?aUZrMlNXNENlb0tIV0dwb3pnUkd1aUxESVJwNnJVTm16MENkZURmTDNkUGpG?=
 =?utf-8?B?WkN4V2Zzc2VudHN2Q3l3bXF3bkRjaW9UZ1dINVRReFBjbG11MHBQd09xNUhp?=
 =?utf-8?B?S2JzbllCY3FOSUFyQW9TYTBsQ200aDZaOGhFb1I5S1dkSG5yT1NvMGZXR0pB?=
 =?utf-8?B?QW82T3hKT1lreTdHRWticXdPY2cyVTF1Rlhqc0lSYkphSkJxT2Nsejk4VHJI?=
 =?utf-8?B?b2ZGNnRFUU5BbHVpakFxNk9pREVueE05V3RQN3ZlRFVSUFZJR0U3Nno5bVA5?=
 =?utf-8?B?UXNJdnJEK3FBWWRpRGxHUjcxWm5YNTBLYWRRM0g1NDhINTRBR0lURDZjRVdD?=
 =?utf-8?B?K2ppcXlNZmV2WTF2bjJDOTBGWVREYVFhTFBWVUgxTFNEU283T3A5ZzBEY1Jw?=
 =?utf-8?B?aTl0T3J0TUpnWmZPb3ZUVFhjalRHOU1aK283VXo3ZmUxYVpSYXd5SVRFbHVQ?=
 =?utf-8?B?d213dzM1SUJvdU0wQlI2NTBqQ2QvcURjRTY5R3lvZ3hvcGJpQ09UaWY3N1hR?=
 =?utf-8?B?RHBmUU0yK0lRWEtaUFBQTTNVUmhER1p1NER6cmZ2b3VvZUJKOTdqd0pSbTRU?=
 =?utf-8?B?d25UVXl3OXM1YjF5UERSVVN1NGlxNnpmVTNjKzZEYmtjU1Fya1UzdzdvUU1E?=
 =?utf-8?B?SGZ4UlhSTzllMjVXSGd1RlpwNG1RQUJpYjdMdDEwb1F5MC9yM1VLd1pOS0Zv?=
 =?utf-8?B?NlRyVm42TENRYXR6S3VNNDNZVVJLYWxoaktZTVZ0VU1obHpXbXE1RXlQdHZ0?=
 =?utf-8?B?L2ZrMlZrdjViMTNOZm95VENHSDVPaHNjQlhLM0NtMDlaVTBaKytycytSQm9C?=
 =?utf-8?B?L3lCQkFUZG45cnBselNPZkxoYVlWR2krN0FjcWtUNFMwUXhzMllSZ0NVQWtv?=
 =?utf-8?B?L0tJZ2JTRUc4TVdZc0xIRU5MZFVUTW9LbFZsRzZ4UDc5MzhGZDJnSG5TczBi?=
 =?utf-8?B?SThVRVdmUUNWMTcrbGxleG92Q0xmS0ZpS3NkUmZXZVFuNm03U09PMVZsMTY2?=
 =?utf-8?B?U1BGK1owQnpieTR0Tk9MZ1Q1ZFltcy85QzlKbm5HYjFqNGJ6akJlc1FWcito?=
 =?utf-8?Q?ViHVMUMkg/K+4wP/gNbO+BkQF?=
X-OriginatorOrg: axentia.se
X-MS-Exchange-CrossTenant-Network-Message-Id: 669b1634-8a49-4f6c-6b2d-08dbd08571c4
X-MS-Exchange-CrossTenant-AuthSource: AM0PR02MB4436.eurprd02.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Oct 2023 09:26:16.2505
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4ee68585-03e1-4785-942a-df9c1871a234
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: OZRWZnZvXlCgJC362ob6AMPewTeEPnmlugJh9IonBbR9Fqv+1ZSu4C/JDM20gSNW
X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR02MB5854
X-Spam-Status: No, score=-4.2 required=5.0 tests=DKIM_SIGNED,DKIM_VALID,
	DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,
	NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS autolearn=unavailable
	autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on morse.vger.email
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (morse.vger.email [0.0.0.0]); Thu, 19 Oct 2023 02:26:38 -0700 (PDT)

Hi!

2023-10-19 at 09:35, Herve Codina wrote:
> i2c-demux-pinctrl uses the pair of_find_i2c_adapter_by_node() /
> i2c_put_adapter(). These pair alone is not correct to properly lock the
> I2C parent adapter.
> 
> Indeed,	i2c_put_adapter() decrements the module refcount while
> of_find_i2c_adapter_by_node() does not increment it. This leads to an
> overflow over zero of the parent adapter user counter.

Perhaps "... underflow of the parent module refcount."?

> 
> Use the	dedicated function, of_get_i2c_adapter_by_node(), to handle
> correctly the module refcount.
> 
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>

Good find!

Fixes: 50a5ba876908 ("i2c: mux: demux-pinctrl: add driver")
Acked-by: Peter Rosin <peda@axentia.se>

Cheers,
Peter

> ---
>  drivers/i2c/muxes/i2c-demux-pinctrl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/muxes/i2c-demux-pinctrl.c b/drivers/i2c/muxes/i2c-demux-pinctrl.c
> index 22f2280eab7f..9f2e4aa28159 100644
> --- a/drivers/i2c/muxes/i2c-demux-pinctrl.c
> +++ b/drivers/i2c/muxes/i2c-demux-pinctrl.c
> @@ -61,7 +61,7 @@ static int i2c_demux_activate_master(struct i2c_demux_pinctrl_priv *priv, u32 ne
>  	if (ret)
>  		goto err;
>  
> -	adap = of_find_i2c_adapter_by_node(priv->chan[new_chan].parent_np);
> +	adap = of_get_i2c_adapter_by_node(priv->chan[new_chan].parent_np);
>  	if (!adap) {
>  		ret = -ENODEV;
>  		goto err_with_revert;