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The net_device is allocated during function instance creation and
registered during the bind phase with the gadget device as its sysfs
parent. When the function unbinds, the parent device is destroyed, but
the net_device survives, resulting in dangling sysfs symlinks:
console:/ # ls -l /sys/class/net/usb0
lrwxrwxrwx ... /sys/class/net/usb0 ->
/sys/devices/platform/.../gadget.0/net/usb0
console:/ # ls -l /sys/devices/platform/.../gadget.0/net/usb0
ls: .../gadget.0/net/usb0: No such file or directory
Use device_move() to reparent the net_device between the gadget device
tree and /sys/devices/virtual across bind and unbind cycles. During the
final unbind, calling device_move(NULL) moves the net_device to the
virtual device tree before the gadget device is destroyed. On rebinding,
device_move() reparents the device back under the new gadget, ensuring
proper sysfs topology and power management ordering.
To maintain compatibility with legacy composite drivers (e.g., multi.c),
the borrowed_net flag is used to indicate whether the network device is
shared and pre-registered during the legacy driver's bind phase.
Fixes: f466c63538 ("usb: gadget: f_rndis: convert to new function interface with backward compatibility")
Cc: stable@vger.kernel.org
Signed-off-by: Kuen-Han Tsai <khtsai@google.com>
Link: https://patch.msgid.link/20260320-usb-net-lifecycle-v1-7-4886b578161b@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
62 lines
1.8 KiB
C
62 lines
1.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* u_rndis.h
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*
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* Utility definitions for the subset function
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*
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* Copyright (c) 2013 Samsung Electronics Co., Ltd.
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* http://www.samsung.com
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*
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* Author: Andrzej Pietrasiewicz <andrzejtp2010@gmail.com>
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*/
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#ifndef U_RNDIS_H
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#define U_RNDIS_H
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#include <linux/usb/composite.h>
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/**
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* struct f_rndis_opts - RNDIS function options
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* @func_inst: USB function instance.
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* @vendor_id: Vendor ID.
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* @manufacturer: Manufacturer string.
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* @net: The net_device associated with the RNDIS function.
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* @bind_count: Tracks the number of configurations the RNDIS function is
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* bound to, preventing double-registration of the @net device.
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* @borrowed_net: True if the net_device is shared and pre-registered during
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* the legacy composite driver's bind phase (e.g., multi.c).
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* If false, the RNDIS function will register the net_device
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* during its own bind phase.
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* @rndis_interf_group: ConfigFS group for RNDIS interface.
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* @rndis_os_desc: USB OS descriptor for RNDIS.
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* @rndis_ext_compat_id: Extended compatibility ID.
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* @class: USB class.
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* @subclass: USB subclass.
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* @protocol: USB protocol.
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* @lock: Protects the data from concurrent access by configfs read/write
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* and create symlink/remove symlink operations.
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* @refcnt: Reference counter for the function instance.
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*/
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struct f_rndis_opts {
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struct usb_function_instance func_inst;
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u32 vendor_id;
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const char *manufacturer;
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struct net_device *net;
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int bind_count;
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bool borrowed_net;
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struct config_group *rndis_interf_group;
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struct usb_os_desc rndis_os_desc;
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char rndis_ext_compat_id[16];
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u8 class;
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u8 subclass;
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u8 protocol;
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struct mutex lock;
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int refcnt;
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};
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void rndis_borrow_net(struct usb_function_instance *f, struct net_device *net);
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#endif /* U_RNDIS_H */
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