From 10078d83ce910ddfee311964766c5042c38d3763 Mon Sep 17 00:00:00 2001
From: Paul Oliver <contact@pauloliver.dev>
Date: Sat, 13 Dec 2025 22:20:41 +0100
Subject: Adds battery monitoring service via INA226/I2C

---
 hsm-battery/Hsm/Battery/FFI.hsc | 58 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 hsm-battery/Hsm/Battery/FFI.hsc

(limited to 'hsm-battery/Hsm/Battery/FFI.hsc')

diff --git a/hsm-battery/Hsm/Battery/FFI.hsc b/hsm-battery/Hsm/Battery/FFI.hsc
new file mode 100644
index 0000000..3ccb5c1
--- /dev/null
+++ b/hsm-battery/Hsm/Battery/FFI.hsc
@@ -0,0 +1,58 @@
+{-# LANGUAGE CApiFFI #-}
+{-# LANGUAGE DeriveAnyClass #-}
+
+module Hsm.Battery.FFI
+  ( I2CMsg (..)
+  , I2CRdWrIoctlData (..)
+  , i2cRdWr
+  , i2cMRd
+  , i2cMNoStart
+  , ioctl
+  )
+where
+
+import Data.Word (Word16, Word32, Word8)
+import Foreign.C.Types (CInt (CInt))
+import Foreign.CStorable (CStorable, cAlignment, cPeek, cPoke, cSizeOf)
+import Foreign.Ptr (Ptr)
+import Foreign.Storable (Storable (..))
+import GHC.Generics (Generic)
+import System.Posix.Types (Fd (Fd))
+
+data I2CMsg = I2CMsg
+  { addr :: Word16
+  , flags :: Word16
+  , len :: Word16
+  , buf :: Ptr Word8
+  }
+  deriving (CStorable, Generic, Show)
+
+instance Storable I2CMsg where
+  sizeOf = cSizeOf
+  alignment = cAlignment
+  poke = cPoke
+  peek = cPeek
+
+data I2CRdWrIoctlData = I2CRdWrIoctlData
+  { msgs :: Ptr I2CMsg
+  , nmsgs :: Word32
+  }
+  deriving (CStorable, Generic, Show)
+
+instance Storable I2CRdWrIoctlData where
+  sizeOf = cSizeOf
+  alignment = cAlignment
+  poke = cPoke
+  peek = cPeek
+
+foreign import capi safe "linux/i2c-dev.h value I2C_RDWR"
+  i2cRdWr :: Int
+
+foreign import capi safe "linux/i2c.h value I2C_M_RD"
+  i2cMRd :: Int
+
+foreign import capi safe "linux/i2c.h value I2C_M_NOSTART"
+  i2cMNoStart :: Int
+
+foreign import capi safe "sys/ioctl.h"
+  ioctl :: Fd -> Int -> Ptr a -> IO Int
-- 
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