[PATCH 6.18 154/333] Revert "usb: gadget: u_ether: add gether_opts for config caching"

Greg Kroah-Hartman
2026-03-17T17:16:08Z

From: Kuen-Han Tsai <khtsai@google.com>

commit 3131c1aff7cdffb96239f06f98e16188cbc2083f upstream.

This reverts commit e065c6a7e46c2ee9c677fdbf50035323d2de1215.

This commit is being reverted as part of a series-wide revert.

By deferring the net_device allocation to the bind() phase, a single
function instance will spawn multiple network devices if it is symlinked
to multiple USB configurations.

This causes regressions for userspace tools (like the postmarketOS DHCP
daemon) that rely on reading the interface name (e.g., "usb0") from
configfs. Currently, configfs returns the template "usb%d", causing the
userspace network setup to fail.

Crucially, because this patch breaks the 1:1 mapping between the
function instance and the network device, this naming issue cannot
simply be patched. Configfs only exposes a single 'ifname' attribute per
instance, making it impossible to accurately report the actual interface
name when multiple underlying network devices can exist for that single
instance.

All configurations tied to the same function instance are meant to share
a single network device. Revert this change to restore the 1:1 mapping
by allocating the network device at the instance level (alloc_inst).

Reported-by: David Heidelberg <david@ixit.cz>
Closes: https://lore.kernel.org/linux-usb/70b558ea-a12e-4170-9b8e-c951131249af@ixit.cz/
Fixes: 56a512a9b410 ("usb: gadget: f_ncm: align net_device lifecycle with bind/unbind")
Cc: stable <stable@kernel.org>
Signed-off-by: Kuen-Han Tsai <khtsai@google.com>
Link: https://patch.msgid.link/20260309-f-ncm-revert-v2-6-ea2afbc7d9b2@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/function/u_ether.c | 30 ----
drivers/usb/gadget/function/u_ether.h | 28 ---
drivers/usb/gadget/function/u_ether_configfs.h | 176 -------------------------
3 files changed, 234 deletions(-)

--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -1039,36 +1039,6 @@ int gether_set_ifname(struct net_device
}
EXPORT_SYMBOL_GPL(gether_set_ifname);

-void gether_setup_opts_default(struct gether_opts *opts, const char *name)
-{
- opts->qmult = QMULT_DEFAULT;
- snprintf(opts->name, sizeof(opts->name), "%s%%d", name);
- eth_random_addr(opts->dev_mac);
- opts->addr_assign_type = NET_ADDR_RANDOM;
- eth_random_addr(opts->host_mac);
-}
-EXPORT_SYMBOL_GPL(gether_setup_opts_default);
-
-void gether_apply_opts(struct net_device *net, struct gether_opts *opts)
-{
- struct eth_dev *dev = netdev_priv(net);
-
- dev->qmult = opts->qmult;
-
- if (opts->ifname_set) {
- strscpy(net->name, opts->name, sizeof(net->name));
- dev->ifname_set = true;
- }
-
- memcpy(dev->host_mac, opts->host_mac, sizeof(dev->host_mac));
-
- if (opts->addr_assign_type == NET_ADDR_SET) {
- memcpy(dev->dev_mac, opts->dev_mac, sizeof(dev->dev_mac));
- net->addr_assign_type = opts->addr_assign_type;
- }
-}
-EXPORT_SYMBOL_GPL(gether_apply_opts);
-
void gether_suspend(struct gether *link)
{
struct eth_dev *dev = link->ioport;
--- a/drivers/usb/gadget/function/u_ether.h
+++ b/drivers/usb/gadget/function/u_ether.h
@@ -38,31 +38,6 @@

struct eth_dev;

-/**
- * struct gether_opts - Options for Ethernet gadget function instances
- * @name: Pattern for the network interface name (e.g., "usb%d").
- * Used to generate the net device name.
- * @qmult: Queue length multiplier for high/super speed.
- * @host_mac: The MAC address to be used by the host side.
- * @dev_mac: The MAC address to be used by the device side.
- * @ifname_set: True if the interface name pattern has been set by userspace.
- * @addr_assign_type: The method used for assigning the device MAC address
- * (e.g., NET_ADDR_RANDOM, NET_ADDR_SET).
- *
- * This structure caches network-related settings provided through configfs
- * before the net_device is fully instantiated. This allows for early
- * configuration while deferring net_device allocation until the function
- * is bound.
- */
-struct gether_opts {
- char name[IFNAMSIZ];
- unsigned int qmult;
- u8 host_mac[ETH_ALEN];
- u8 dev_mac[ETH_ALEN];
- bool ifname_set;
- unsigned char addr_assign_type;
-};
-
/*
* This represents the USB side of an "ethernet" link, managed by a USB
* function which provides control and (maybe) framing. Two functions
@@ -284,9 +259,6 @@ int gether_set_ifname(struct net_device

void gether_cleanup(struct eth_dev *dev);

-void gether_setup_opts_default(struct gether_opts *opts, const char *name);
-void gether_apply_opts(struct net_device *net, struct gether_opts *opts);
-
void gether_suspend(struct gether *link);
void gether_resume(struct gether *link);

--- a/drivers/usb/gadget/function/u_ether_configfs.h
+++ b/drivers/usb/gadget/function/u_ether_configfs.h
@@ -13,12 +13,6 @@
#ifndef __U_ETHER_CONFIGFS_H
#define __U_ETHER_CONFIGFS_H

-#include <linux/cleanup.h>
-#include <linux/if_ether.h>
-#include <linux/mutex.h>
-#include <linux/netdevice.h>
-#include <linux/rtnetlink.h>
-
#define USB_ETHERNET_CONFIGFS_ITEM(_f_) \
static void _f_##_attr_release(struct config_item *item) \
{ \
@@ -203,174 +197,4 @@ out: \
\
CONFIGFS_ATTR(_f_##_opts_, _n_)

-#define USB_ETHER_OPTS_ITEM(_f_) \
- static void _f_##_attr_release(struct config_item *item) \
- { \
- struct f_##_f_##_opts *opts = to_f_##_f_##_opts(item); \
- \
- usb_put_function_instance(&opts->func_inst); \
- } \
- \
- static struct configfs_item_operations _f_##_item_ops = { \
- .release = _f_##_attr_release, \
- }
-
-#define USB_ETHER_OPTS_ATTR_DEV_ADDR(_f_) \
- static ssize_t _f_##_opts_dev_addr_show(struct config_item *item, \
- char *page) \
- { \
- struct f_##_f_##_opts *opts = to_f_##_f_##_opts(item); \
- \
- guard(mutex)(&opts->lock); \
- return sysfs_emit(page, "%pM\n", opts->net_opts.dev_mac); \
- } \
- \
- static ssize_t _f_##_opts_dev_addr_store(struct config_item *item, \
- const char *page, size_t len) \
- { \
- struct f_##_f_##_opts *opts = to_f_##_f_##_opts(item); \
- u8 new_addr[ETH_ALEN]; \
- const char *p = page; \
- \
- guard(mutex)(&opts->lock); \
- if (opts->refcnt) \
- return -EBUSY; \
- \
- for (int i = 0; i < ETH_ALEN; i++) { \
- unsigned char num; \
- if ((*p == '.') || (*p == ':')) \
- p++; \
- num = hex_to_bin(*p++) << 4; \
- num |= hex_to_bin(*p++); \
- new_addr[i] = num; \
- } \
- if (!is_valid_ether_addr(new_addr)) \
- return -EINVAL; \
- memcpy(opts->net_opts.dev_mac, new_addr, ETH_ALEN); \
- opts->net_opts.addr_assign_type = NET_ADDR_SET; \
- return len; \
- } \
- \
- CONFIGFS_ATTR(_f_##_opts_, dev_addr)
-
-#define USB_ETHER_OPTS_ATTR_HOST_ADDR(_f_) \
- static ssize_t _f_##_opts_host_addr_show(struct config_item *item, \
- char *page) \
- { \
- struct f_##_f_##_opts *opts = to_f_##_f_##_opts(item); \
- \
- guard(mutex)(&opts->lock); \
- return sysfs_emit(page, "%pM\n", opts->net_opts.host_mac); \
- } \
- \
- static ssize_t _f_##_opts_host_addr_store(struct config_item *item, \
- const char *page, size_t len) \
- { \
- struct f_##_f_##_opts *opts = to_f_##_f_##_opts(item); \
- u8 new_addr[ETH_ALEN]; \
- const char *p = page; \
- \
- guard(mutex)(&opts->lock); \
- if (opts->refcnt) \
- return -EBUSY; \
- \
- for (int i = 0; i < ETH_ALEN; i++) { \
- unsigned char num; \
- if ((*p == '.') || (*p == ':')) \
- p++; \
- num = hex_to_bin(*p++) << 4; \
- num |= hex_to_bin(*p++); \
- new_addr[i] = num; \
- } \
- if (!is_valid_ether_addr(new_addr)) \
- return -EINVAL; \
- memcpy(opts->net_opts.host_mac, new_addr, ETH_ALEN); \
- return len; \
- } \
- \
- CONFIGFS_ATTR(_f_##_opts_, host_addr)
-
-#define USB_ETHER_OPTS_ATTR_QMULT(_f_) \
- static ssize_t _f_##_opts_qmult_show(struct config_item *item, \
- char *page) \
- { \
- struct f_##_f_##_opts *opts = to_f_##_f_##_opts(item); \
- \
- guard(mutex)(&opts->lock); \
- return sysfs_emit(page, "%u\n", opts->net_opts.qmult); \
- } \
- \
- static ssize_t _f_##_opts_qmult_store(struct config_item *item, \
- const char *page, size_t len) \
- { \
- struct f_##_f_##_opts *opts = to_f_##_f_##_opts(item); \
- u32 val; \
- int ret; \
- \
- guard(mutex)(&opts->lock); \
- if (opts->refcnt) \
- return -EBUSY; \
- \
- ret = kstrtou32(page, 0, &val); \
- if (ret) \
- return ret; \
- \
- opts->net_opts.qmult = val; \
- return len; \
- } \
- \
- CONFIGFS_ATTR(_f_##_opts_, qmult)
-
-#define USB_ETHER_OPTS_ATTR_IFNAME(_f_) \
- static ssize_t _f_##_opts_ifname_show(struct config_item *item, \
- char *page) \
- { \
- struct f_##_f_##_opts *opts = to_f_##_f_##_opts(item); \
- const char *name; \
- \
- guard(mutex)(&opts->lock); \
- rtnl_lock(); \
- if (opts->net_opts.ifname_set) \
- name = opts->net_opts.name; \
- else if (opts->net) \
- name = netdev_name(opts->net); \
- else \
- name = "(inactive net_device)"; \
- rtnl_unlock(); \
- return sysfs_emit(page, "%s\n", name); \
- } \
- \
- static ssize_t _f_##_opts_ifname_store(struct config_item *item, \
- const char *page, size_t len) \
- { \
- struct f_##_f_##_opts *opts = to_f_##_f_##_opts(item); \
- char tmp[IFNAMSIZ]; \
- const char *p; \
- size_t c_len = len; \
- \
- if (c_len > 0 && page[c_len - 1] == '\n') \
- c_len--; \
- \
- if (c_len >= sizeof(tmp)) \
- return -E2BIG; \
- \
- strscpy(tmp, page, c_len + 1); \
- if (!dev_valid_name(tmp)) \
- return -EINVAL; \
- \
- /* Require exactly one %d */ \
- p = strchr(tmp, '%'); \
- if (!p || p[1] != 'd' || strchr(p + 2, '%')) \
- return -EINVAL; \
- \
- guard(mutex)(&opts->lock); \
- if (opts->refcnt) \
- return -EBUSY; \
- strscpy(opts->net_opts.name, tmp, sizeof(opts->net_opts.name)); \
- opts->net_opts.ifname_set = true; \
- return len; \
- } \
- \
- CONFIGFS_ATTR(_f_##_opts_, ifname)
-
#endif /* __U_ETHER_CONFIGFS_H */