netdev - Re: [net-next v4 2/8] net: wwan: core: split port creation and registration

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Message-ID: <af3aba1d-984b-46e1-824f-8cdbd774f89f@gmail.com>
Date: Thu, 8 Jan 2026 02:42:54 +0200
From: Sergey Ryazanov <ryazanov.s.a@...il.com>
To: Slark Xiao <slark_xiao@....com>,
 Sai Krishna Gajula <saikrishnag@...vell.com>
Cc: "loic.poulain@....qualcomm.com" <loic.poulain@....qualcomm.com>,
 "johannes@...solutions.net" <johannes@...solutions.net>,
 "andrew+netdev@...n.ch" <andrew+netdev@...n.ch>,
 "davem@...emloft.net" <davem@...emloft.net>,
 "edumazet@...gle.com" <edumazet@...gle.com>,
 "kuba@...nel.org" <kuba@...nel.org>, "pabeni@...hat.com"
 <pabeni@...hat.com>, "mani@...nel.org" <mani@...nel.org>,
 "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [net-next v4 2/8] net: wwan: core: split port creation and
 registration

On 1/7/26 09:21, Slark Xiao wrote:
> At 2026-01-07 00:49:50, "Sai Krishna Gajula" <saikrishnag@...vell.com> wrote:
>>> -----Original Message-----
>>> From: Slark Xiao <slark_xiao@....com>
>>> Sent: Monday, January 5, 2026 3:50 PM
>>> To: loic.poulain@....qualcomm.com; ryazanov.s.a@...il.com;
>>> johannes@...solutions.net; andrew+netdev@...n.ch;
>>> davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org;
>>> pabeni@...hat.com; mani@...nel.org
>>> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org
>>> Subject: [net-next v4 2/8] net: wwan: core: split port creation and
>>> registration
>>>
>>> From: Sergey Ryazanov <ryazanov. s. a@ gmail. com> Upcoming GNSS (NMEA)
>>> port type support requires exporting it via the GNSS subsystem. On another
>>> hand, we still need to do basic WWAN core work: find or allocate the WWAN
>>> device, make it the
>>> From: Sergey Ryazanov <ryazanov.s.a@...il.com>
>>>
>>> Upcoming GNSS (NMEA) port type support requires exporting it via the GNSS
>>> subsystem. On another hand, we still need to do basic WWAN core
>>> work: find or allocate the WWAN device, make it the port parent, etc. To reuse
>>> as much code as possible, split the port creation function into the registration
>>> of a regular WWAN port device, and basic port struct initialization.
>>>
>>> To be able to use put_device() uniformly, break the device_register() call into
>>> device_initialize() and device_add() and call device initialization earlier.

[skipped]

>>> +	struct wwan_device *wwandev = to_wwan_dev(port->dev.parent);
>>> +	char namefmt[0x20];
>>> +	int minor, err;
>>> +
>>> +	/* A port is exposed as character device, get a minor */
>>> +	minor = ida_alloc_range(&minors, 0, WWAN_MAX_MINORS - 1,
>>> GFP_KERNEL);
>>> +	if (minor < 0)
>>> +		return minor;
>>> +
>>> +	port->dev.class = &wwan_class;
>>> +	port->dev.devt = MKDEV(wwan_major, minor);
>>> +
>>> +	/* allocate unique name based on wwan device id, port type and
>>> number */
>>> +	snprintf(namefmt, sizeof(namefmt), "wwan%u%s%%d", wwandev-
>>>> id,
>>> +		 wwan_port_types[port->type].devsuf);
>>> +
>>> +	/* Serialize ports registration */
>>> +	mutex_lock(&wwan_register_lock);
>>> +
>>> +	__wwan_port_dev_assign_name(port, namefmt);
>>> +	err = device_add(&port->dev);
>>> +
>>> +	mutex_unlock(&wwan_register_lock);
>>> +
>>> +	if (err)
>>> +		return err;
>> Please check, if freeing with ida_free is required before returning err.
>> if (err) {
>>     ida_free(&minors, minor);
>>     return err;
>> }
> Yes, you are right.
> And patch 7/8 modifies this file as well. We need to align with that changes
> since there are some issues(we still allocates the minor even the cdev is
> false). This would lead to the release function can't release the correct
> devt.

Sai, nice catch! It should free the minor number on error exactly like this.

--
Sergey