package: new package for usb gadget setup

Setting up usb gadgets using g_* kernel modules are considered a
legacy approach, but the usb_gadget configfs is a bit annoying
to use directly.
The usb_gadget configfs works by creating magic directories
and writing to magic files under /sys/kernel/config/usbgadget.
This new package is an init script to setup usb_gadget configfs
using uci. In the config file, gadget/configuration/function
sections create corresponding directories. UCI options are magic
files available in the configfs and strings/0x409 directories,
grabbed with a 'find' command. UDC option in gadget writes
the UDC file under the 'gadget' directory to attach the
generated gadget config.

It's also possible to apply pre-made config templates under
/usr/share/usbgadget. The templates use the same UCI config
format, with the 'gadget' entry named 'g1'. Currently, there
are templates for CDC-ACM and CDC-NCM gadgets written based
on existing g_*.ko module code.

Certain SBCs come with only a USB device port (e.g. Raspberry Pi
Zero). With this script, it's now possible to perform initial
setup on them by adding a default NCM gadget.

Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
This commit is contained in:
Chuanhong Guo 2023-11-19 20:56:52 +08:00
parent b799dd3c70
commit b196a9f6ce
5 changed files with 236 additions and 0 deletions

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include $(TOPDIR)/rules.mk
PKG_NAME:=usbgadget
PKG_RELEASE:=1
PKG_LICENSE:=BSD-2-Clause
PKG_MAINTAINER:=Chuanhong Guo <gch981213@gmail.com>
include $(INCLUDE_DIR)/package.mk
define Package/$(PKG_NAME)
SECTION:=utils
CATEGORY:=Utilities
DEPENDS:=@USB_GADGET_SUPPORT +kmod-usb-gadget +kmod-usb-lib-composite
TITLE:=init script to create USB gadgets
endef
define Build/Compile
endef
define Package/$(PKG_NAME)/install
$(INSTALL_DIR) $(1)/etc/config $(1)/etc/init.d
$(INSTALL_CONF) ./files/usbgadget.conf $(1)/etc/config/usbgadget
$(INSTALL_BIN) ./files/usbgadget.init $(1)/etc/init.d/usbgadget
endef
$(eval $(call BuildPackage,$(PKG_NAME)))
# 1: short name
# 2: description
# 3: dependencies on other packages
define GadgetPreset
define Package/$(PKG_NAME)-$(1)
SECTION:=utils
CATEGORY:=Utilities
TITLE+= $(2) gadget preset
DEPENDS+= $(3)
endef
define Package/$(PKG_NAME)-$(1)/description
This package contains the USB gadget preset for $(3).
endef
define Package/$(PKG_NAME)-$(1)/install
$(INSTALL_DIR) $$(1)/usr/share/usbgadget
$(INSTALL_CONF) ./files/presets/$(1) $$(1)/usr/share/usbgadget
endef
$$(eval $$(call BuildPackage,$(PKG_NAME)-$(1)))
endef
$(eval $(call GadgetPreset,ncm,CDC-NCM,+kmod-usb-gadget-ncm))
$(eval $(call GadgetPreset,acm,CDC-ACM,+kmod-usb-gadget-serial))

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config gadget 'g1'
option idVendor '0x0525'
option idProduct '0xa4a7'
option bDeviceClass '2'
option product 'Gadget Serial v2.4'
config configuration 'cfg1'
option configuration 'ACM'
option gadget 'g1'
config function 'acm1'
option function 'acm'
option configuration 'cfg1'

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config gadget 'g1'
option idVendor '0x0525'
option idProduct '0xa4a1'
option bDeviceClass '2'
option product 'NCM Gadget'
config configuration 'cfg1'
option configuration 'NCM'
option gadget 'g1'
config function 'ncm1'
option function 'ncm'
option configuration 'cfg1'

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# apply a preset under /usr/share/usbgadget
config preset
option name 'ncm'
# specify a UDC to enable this gadget:
# option UDC 'musb-hdrc.2.auto'
# or create a custom gadget here following the content of presets:
#config gadget 'g1'
# option idVendor ...
# ...
# and add an UDC under the gadget section to enable it:
# option UDC 'musb-hdrc.2.auto'

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#!/bin/sh /etc/rc.common
START=19
GADGET_FS=/sys/kernel/config/usb_gadget
GADGET_PRESETS_DIR=/usr/share/usbgadget
GADGET_PREFIX=owrt_
log() {
logger -t usbgadget "$@"
}
apply_configs() {
local fs_path="$1"
local cfg="$2"
for param in $(find "$fs_path" -maxdepth 1 -type f -exec basename '{}' ';'); do
[ "$param" = "UDC" ] && continue
config_get val "$cfg" "$param"
[ -n "$val" ] && echo "$val" > "${fs_path}/${param}"
done
}
setup_gadget() {
local cfg="$1"
local gadget_path="${GADGET_FS}/${GADGET_PREFIX}${cfg}"
local param udc
config_get udc "$cfg" UDC
[ -z "$udc" ] && return
mkdir "$gadget_path" || return
apply_configs "$gadget_path" "$cfg"
local strings_path="${gadget_path}/strings/0x409"
mkdir "$strings_path"
apply_configs "$strings_path" "$cfg"
}
setup_configuration() {
local cfg="$1"
local gadget
config_get gadget "$cfg" gadget
local cfgs_path="${GADGET_FS}/${GADGET_PREFIX}${gadget}/configs"
[ -d "${cfgs_path}" ] || return
local cfg_path="${cfgs_path}/${cfg}.1"
mkdir "$cfg_path" || {
log "failed to create configuration ${cfg}"
return
}
apply_configs "$cfg_path" "$cfg"
local strings_path="${cfg_path}/strings/0x409"
mkdir "$strings_path"
apply_configs "$strings_path" "$cfg"
}
setup_function() {
local cfg="$1"
local usbcfg gadget usbfun
config_get usbcfg "$cfg" configuration
[ -z "$usbcfg" ] && return
config_get usbfun "$cfg" function
[ -z "$usbfun" ] && return
config_get gadget "$usbcfg" gadget
local gadget_path="${GADGET_FS}/${GADGET_PREFIX}${gadget}"
local cfg_path="${gadget_path}/configs/${usbcfg}.1"
[ -d "${cfg_path}" ] || return
local fun_path="${gadget_path}/functions/${usbfun}.${cfg}"
mkdir "$fun_path" || {
log "failed to create function ${usbfun}.${cfg}"
return
}
apply_configs "$fun_path" "$cfg"
ln -s "$fun_path" "$cfg_path"
}
attach_gadget() {
local cfg="$1"
local gadget_path="${GADGET_FS}/${GADGET_PREFIX}${cfg}"
local param udc
config_get udc "$cfg" UDC
[ -z "$udc" ] && return
echo "$udc" > "$gadget_path/UDC"
}
load_gadget() {
config_foreach setup_gadget gadget
config_foreach setup_configuration configuration
config_foreach setup_function function
config_foreach attach_gadget gadget
}
# use subshell for isolated env
apply_preset() (
local preset="$1"
local gadget="$2"
UCI_CONFIG_DIR=$GADGET_PRESETS_DIR config_load "$1"
config_set g1 UDC "$2"
load_gadget
)
load_preset() {
local cfg="$1"
config_get name "$cfg" name
config_get udc "$cfg" UDC
[ -z "$udc" ] && return
apply_preset $name $udc
}
start() {
grep -q /sys/kernel/config /proc/mounts || \
mount -t configfs configfs /sys/kernel/config
[ -d /sys/kernel/config/usb_gadget ] || {
log "usb_gadget support not found."
return 1
}
config_load usbgadget
config_foreach load_preset preset
load_gadget
}
stop() {
for gadget_path in ${GADGET_FS}/${GADGET_PREFIX}* ; do
[ -d "$gadget_path" ] || continue
echo "" > ${gadget_path}/UDC
find ${gadget_path}/configs -maxdepth 2 -type l -exec rm '{}' ';'
rmdir ${gadget_path}/configs/*/strings/*
rmdir ${gadget_path}/configs/*
rmdir ${gadget_path}/functions/*
rmdir ${gadget_path}/strings/*
rmdir $gadget_path
done
}