Support auto-detection of input devices via fbink_input (#11807)

* Kobo: Drop a bunch of if ladder crap and switch to auto-detection of input devices via fbink_input
* Kindle: Drop an even larger bundle of crap to do the same ;p. (re: #11392)
* ExternalKeyboard: Switch to fbink_input to whitelist keyboards instead of the manual parsing of caps via its FindKeyboard class
* Input: Extended open/close wrappers to handle logging & tracking of dupe open/close calls.

frontend/device/input.lua

@@ -195,6 +195,10 @@ local Input = {
     setClipboardText = function(text)
         _internal_clipboard_text = text or ""
     end,
+
+    -- open'ed input devices hashmap (key: path, value: fd number)
+    -- Must be a class member, both because Input is a singleton and that state is process-wide anyway.
+    opened_devices = {},
 }
 
 function Input:new(o)
@@ -295,14 +299,74 @@ function Input:disableRotationMap()
 end
 
 --[[--
-Wrapper for FFI input open.
+Wrapper for our Lua/C input module's open.
 
 Note that we adhere to the "." syntax here for compatibility.
 
-@todo Clean up separation FFI/this.
+The `name` argument is optional, and used for logging purposes only.
 --]]
-function Input.open(device, is_emu_events)
-    return input.open(device, is_emu_events and 1 or 0)
+function Input.open(path, name)
+    -- Make sure we don't open the same device twice.
+    if not Input.opened_devices[path] then
+        local fd = input.open(path)
+        if fd then
+            Input.opened_devices[path] = fd
+            if name then
+                logger.dbg("Opened fd", fd, "for input device", name, "@", path)
+            else
+                logger.dbg("Opened fd", fd, "for input device @", path)
+            end
+        end
+        -- No need to log failures, input will have raised an error already,
+        -- and we want to make those fatal, so we don't protect this call.
+        return fd
+    end
+end
+
+--[[--
+Wrapper for our Lua/C input module's close.
+
+Note that we adhere to the "." syntax here for compatibility.
+--]]
+function Input.close(path)
+    -- Make sure we actually know about this device
+    local fd = Input.opened_devices[path]
+    if fd then
+        local ok, err = input.close(fd)
+        if ok or err == C.ENODEV then
+            -- Either the call succeeded,
+            -- or the backend had already caught an ENODEV in waitForInput and closed the fd internally.
+            -- (Because the EvdevInputRemove Event comes from an UsbDevicePlugOut uevent forwarded as an... *input* EV_KEY event ;)).
+            -- Regardless, that device is gone, so clear its spot in the hashmap.
+            Input.opened_devices[path] = nil
+        end
+    else
+        logger.warn("Tried to close an unknown input device @", path)
+    end
+end
+
+--[[--
+Wrapper for our Lua/C input module's closeAll.
+
+Note that we adhere to the "." syntax here for compatibility.
+--]]
+function Input.teardown()
+    input.closeAll()
+    Input.opened_devices = {}
+end
+
+-- Wrappers for the custom FFI implementations with no concept of paths or fd
+if input.is_ffi then
+    -- Pass args as-is. None of 'em actually *take* arguments, but some may be invoked as methods...
+    function Input.open(...)
+        return input.open(...)
+    end
+    function Input.close(...)
+        return input.close(...)
+    end
+    function Input.teardown(...)
+        return input.closeAll(...)
+    end
 end
 
 --[[--