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diff --git a/hsm-gpio/Hsm/GPIO/Lib.hsc b/hsm-gpio/Hsm/GPIO/Lib.hsc
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+{-# LANGUAGE CPP #-}
+{-# LANGUAGE ForeignFunctionInterface #-}
+
+-- This module provides C bindings to the `gpiod` library for direct GPIO pin
+-- control. It includes bindings only for the C functions that are currently
+-- used. In the future, creating a complete set of bindings for the entire
+-- `gpiod` library as an external package would be a valuable contribution to
+-- Hackage.
+
+module Hsm.GPIO.Lib
+  ( chipOpen
+  , chipClose
+  , input
+  , output
+  , LineValue
+  , active
+  , inactive
+  , lineSettingsNew
+  , lineSettingsFree
+  , lineSettingsSetDirection
+  , lineSettingsSetOutputValue
+  , lineConfigNew
+  , lineConfigFree
+  , lineConfigAddLineSettings
+  , requestConfigNew
+  , requestConfigFree
+  , requestConfigSetConsumer
+  , requestLines
+  , LineRequest
+  , lineRequestRelease
+  , lineRequestSetValue
+  , lineRequestSetValues
+  ) where
+
+#include <gpiod.h>
+
+import Foreign.C.String (CString)
+import Foreign.C.Types (CInt(CInt), CSize(CSize), CUInt(CUInt))
+import Foreign.Ptr (Ptr)
+import Foreign.Storable (Storable)
+
+data Chip
+
+foreign import ccall unsafe "gpiod.h gpiod_chip_open"
+  chipOpen :: CString -> IO (Ptr Chip)
+
+foreign import ccall unsafe "gpiod.h gpiod_chip_close"
+  chipClose :: Ptr Chip -> IO ()
+
+data LineSettings
+
+newtype LineDirection =
+  LineDirection CInt
+  deriving (Show)
+
+#{enum LineDirection, LineDirection
+  , input = GPIOD_LINE_DIRECTION_INPUT
+  , output = GPIOD_LINE_DIRECTION_OUTPUT
+}
+
+newtype LineValue =
+  LineValue CInt
+  deriving (Show, Storable)
+
+#{enum LineValue, LineValue
+  , active = GPIOD_LINE_VALUE_ACTIVE
+  , inactive = GPIOD_LINE_VALUE_INACTIVE
+}
+
+foreign import ccall unsafe "gpiod.h gpiod_line_settings_new"
+  lineSettingsNew :: IO (Ptr LineSettings)
+
+foreign import ccall unsafe "gpiod.h gpiod_line_settings_free"
+  lineSettingsFree :: Ptr LineSettings -> IO ()
+
+foreign import ccall unsafe "gpiod.h gpiod_line_settings_set_direction"
+  lineSettingsSetDirection :: Ptr LineSettings -> LineDirection -> IO CInt
+
+foreign import ccall unsafe "gpiod.h gpiod_line_settings_set_output_value"
+  lineSettingsSetOutputValue :: Ptr LineSettings -> LineValue -> IO CInt
+
+data LineConfig
+
+foreign import ccall unsafe "gpiod.h gpiod_line_config_new"
+  lineConfigNew :: IO (Ptr LineConfig)
+
+foreign import ccall unsafe "gpiod.h gpiod_line_config_free"
+  lineConfigFree :: Ptr LineConfig -> IO ()
+
+foreign import ccall unsafe "gpiod.d gpiod_line_config_add_line_settings"
+  lineConfigAddLineSettings :: Ptr LineConfig -> Ptr CUInt -> CSize -> Ptr LineSettings -> IO CInt
+
+data RequestConfig
+
+foreign import ccall unsafe "gpiod.h gpiod_request_config_new"
+  requestConfigNew :: IO (Ptr RequestConfig)
+
+foreign import ccall unsafe "gpiod.h gpiod_request_config_free"
+  requestConfigFree :: Ptr RequestConfig -> IO ()
+
+foreign import ccall unsafe "gpiod.h gpiod_request_config_set_consumer"
+  requestConfigSetConsumer :: Ptr RequestConfig -> CString -> IO ()
+
+data LineRequest
+
+foreign import ccall unsafe "gpiod.h gpiod_chip_request_lines"
+  requestLines :: Ptr Chip -> Ptr RequestConfig -> Ptr LineConfig -> IO (Ptr LineRequest)
+
+foreign import ccall unsafe "gpiod.h gpiod_line_request_release"
+  lineRequestRelease :: Ptr LineRequest -> IO ()
+
+foreign import ccall unsafe "gpiod.h gpiod_line_request_set_value"
+  lineRequestSetValue :: Ptr LineRequest -> CUInt -> LineValue -> IO CInt
+
+foreign import ccall unsafe "gpiod.h gpiod_line_request_set_values"
+  lineRequestSetValues :: Ptr LineRequest -> Ptr LineValue -> IO CInt