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March 2, 2020 22:54
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Configuring an HID device by "manually" interacting with ConfigFS via /sys/kernel/config
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defmodule ElixirKeeb.ManualConfig do | |
@moduledoc """ | |
Manually create a Keyboard HID and writes to its device. | |
""" | |
@usb_gadget_root "/sys/kernel/config/usb_gadget" | |
def configure_device do | |
create_gadget_dir("mygadget") | |
write_to_gadget_file("mygadget/idVendor", "0x1d6b") | |
write_to_gadget_file("mygadget/idProduct", "0x0104") | |
write_to_gadget_file("mygadget/bcdDevice", "0x0100") | |
write_to_gadget_file("mygadget/bcdUSB", "0x0200") | |
create_gadget_dir("mygadget/strings/0x409") | |
write_to_gadget_file("mygadget/strings/0x409/serialnumber", "fedcba9876543210") | |
write_to_gadget_file("mygadget/strings/0x409/manufacturer", "Easter Lejboua") | |
write_to_gadget_file("mygadget/strings/0x409/product", "Lejboua USB device") | |
create_gadget_dir("mygadget/configs/c.1/strings/0x409") | |
write_to_gadget_file("mygadget/configs/c.1/strings/0x409/configuration", "Config 1: HID device") | |
create_gadget_dir("mygadget/functions/hid.usb0") | |
write_to_gadget_file("mygadget/functions/hid.usb0/protocol", "1") | |
write_to_gadget_file("mygadget/functions/hid.usb0/subclass", "1") | |
write_to_gadget_file("mygadget/functions/hid.usb0/report_length", "8") | |
report_desc = "\x05\x01\x09\x06\xa1\x01\x05\x07\x19\xe0\x29\xe7\x15\x00\x25\x01\x75\x01\x95\x08\x81\x02\x95\x01\x75\x08\x81\x03\x95\x05\x75\x01\x05\x08\x19\x01\x29\x05\x91\x02\x95\x01\x75\x03\x91\x03\x95\x06\x75\x08\x15\x00\x25\x65\x05\x07\x19\x00\x29\x65\x81\x00\xc0" | |
write_to_gadget_file("mygadget/functions/hid.usb0/report_desc", report_desc) | |
existing = Path.join(@usb_gadget_root, "mygadget/functions/hid.usb0") | |
new = Path.join(@usb_gadget_root, "mygadget/configs/c.1/hid.usb0") | |
# to remove the device, it's just a matter of | |
# rm'ing the symlink | |
:ok = File.ln_s(existing, new) | |
# we only have one USB device | |
[usb_device] = File.ls!("/sys/class/udc") | |
write_to_gadget_file("mygadget/UDC", usb_device) | |
end | |
@doc """ | |
Works like mkdir -p, if it is passed a hierarchy of folders, | |
say /a/b/c/d/e/f/g/i, it will create them on the USB gadget root, | |
given by @usb_gadget_root | |
""" | |
defp create_gadget_dir(dir) do | |
dir | |
|> String.split("/") | |
|> Enum.reject(&(String.length(&1) == 0)) | |
|> Enum.reduce([], fn (dir, acc) -> | |
to_create = acc | |
|> Enum.reverse() | |
|> Enum.join("/") | |
|> Kernel.<>("/" <> dir) | |
:ok = Path.join(@usb_gadget_root, to_create) | |
|> create_if_not_exists() | |
[dir | acc] | |
end) | |
end | |
defp create_if_not_exists(dir) do | |
case File.exists?(dir) do | |
true -> :ok | |
_ -> File.mkdir(dir) | |
end | |
end | |
defp write_to_gadget_file(path, content) do | |
path_to_write = Path.join(@usb_gadget_root, path) | |
:ok = File.write(path_to_write, content) | |
end | |
end |
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