[openwrt/openwrt] kernel: add option for USB FunctionFS gadget

[LEDE Commits]

hauke pushed a commit to openwrt/openwrt.git, branch openwrt-25.12:
https://git.openwrt.org/8bf13dcb36940f2d656ea8d24cbdf4320bee5e72

commit 8bf13dcb36940f2d656ea8d24cbdf4320bee5e72
Author: Dominic Germain <dominic at germain.cc>
AuthorDate: Fri Dec 19 09:46:57 2025 -0500

    kernel: add option for USB FunctionFS gadget
    
    Add menuconfig option 'kmod-usb-gadget-fs' for the USB FunctionFS gadget
    module
    
    OpenWRT is perfect for USB gadgets that are network-enabled, since it
    provides everything needed to easily manage the device. Having support
    for the FunctionFS gadget enables the use of any custom USB devices
    that does not have a specific module, like Media Transfer Protocol.
    
    Signed-off-by: Dominic Germain <dominic at germain.cc>
    Link: https://github.com/openwrt/openwrt/pull/21207
    Signed-off-by: Hauke Mehrtens <hauke at hauke-m.de>
    (cherry picked from commit 22a69dfa4a9a04833aaac62b9f0a7814571b9e07)
---
 package/kernel/linux/modules/usb.mk | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/package/kernel/linux/modules/usb.mk b/package/kernel/linux/modules/usb.mk
index d484c3a8f8..7d99933725 100644
--- a/package/kernel/linux/modules/usb.mk
+++ b/package/kernel/linux/modules/usb.mk
@@ -154,6 +154,24 @@ endef
 
 $(eval $(call KernelPackage,usb-gadget-hid))
 
+define KernelPackage/usb-gadget-fs
+  TITLE:=USB FunctionFS Gadget Support
+  KCONFIG:=CONFIG_USB_FUNCTIONFS \
+    CONFIG_USB_FUNCTIONFS_ETH=n \
+    CONFIG_USB_FUNCTIONFS_RNDIS=n
+  FILES:= \
+	  $(LINUX_DIR)/drivers/usb/gadget/legacy/g_ffs.ko \
+	  $(LINUX_DIR)/drivers/usb/gadget/function/usb_f_fs.ko
+  AUTOLOAD:=$(call AutoLoad,52,usb_f_fs)
+  $(call AddDepends/usbgadget,+kmod-usb-lib-composite +kmod-dma-buf)
+endef
+
+define KernelPackage/usb-gadget-fs/description
+  Kernel support for USB FunctionFS Gadget.
+endef
+
+$(eval $(call KernelPackage,usb-gadget-fs))
+
 define KernelPackage/usb-gadget-ehci-debug
   TITLE:=USB EHCI debug port Gadget support
   KCONFIG:=\