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111 lines
3.3 KiB
Lua
111 lines
3.3 KiB
Lua
local bit = require("bit")
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local ffi = require("ffi")
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local lfs = require("libs/libkoreader-lfs")
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-- Constants from the linux kernel input-event-codes.h
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local KEY_UP = 103
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local BTN_DPAD_UP = 0x220
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local FindKeyboard = {}
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local function count_set_bits(n)
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-- Brian Kernighan's algorithm
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local count = 0
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while n ~= 0 do
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count = count + 1
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n = bit.band(n, n - 1)
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end
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return count
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end
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local function capabilities_str_to_long_bitmap_array(str)
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-- The format for capabilities is at include/linux/mod_devicetable.h.
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-- They are long's split by spaces. See linux/drivers/input/input.c::input_print_bitmap.
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local long_bitmap_arr = {}
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for c in str:gmatch "([0-9a-fA-F]+)" do
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local long_bitmap = tonumber(c, 16)
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table.insert(long_bitmap_arr, 1, long_bitmap)
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end
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return long_bitmap_arr
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end
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local function count_set_bits_in_array(arr)
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local count = 0
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for __, number in ipairs(arr) do
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local count_in_number = count_set_bits(number)
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count = count + count_in_number
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end
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return count
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end
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local function is_capabilities_bit_set(long_bitmap_arr, bit_offset)
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local long_bitsize = ffi.sizeof("long") * 8
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local arr_index = math.floor(bit_offset / long_bitsize)
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local long_mask = bit.lshift(1, bit_offset % long_bitsize)
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local long_bitmap = long_bitmap_arr[arr_index + 1] -- Array index starts from 1 in Lua
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if long_bitmap then
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return bit.band(long_bitmap, long_mask) ~= 0
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else
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return false
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end
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end
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local function read_key_capabilities(sys_event_path)
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local key_path = sys_event_path .. "/device/capabilities/key"
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local file = io.open(key_path, "r")
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if not file then
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-- This should not happen - the kernel creates key capabilities file for all devices.
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return nil
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end
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local keys_bitmap_str = file:read("l")
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file:close()
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return capabilities_str_to_long_bitmap_array(keys_bitmap_str)
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end
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local function analyze_key_capabilities(long_bitmap_arr)
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-- The heuristic is that a keyboard has at least as many keys as there are alphabet letters and some more.
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local keyboard_min_number_keys = 64
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local keys_count = count_set_bits_in_array(long_bitmap_arr)
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local is_keyboard = keys_count >= keyboard_min_number_keys
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local has_dpad = is_capabilities_bit_set(long_bitmap_arr, KEY_UP) or
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is_capabilities_bit_set(long_bitmap_arr, BTN_DPAD_UP)
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return {
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is_keyboard = is_keyboard,
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has_dpad = has_dpad,
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}
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end
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function FindKeyboard:check(event_file_name)
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local capabilities_long_bitmap_arr = read_key_capabilities("/sys/class/input/" .. event_file_name)
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if capabilities_long_bitmap_arr then
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local keyboard_info = analyze_key_capabilities(capabilities_long_bitmap_arr)
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if keyboard_info.is_keyboard then
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return {
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event_path = "/dev/input/" .. event_file_name,
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has_dpad = keyboard_info.has_dpad
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}
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end
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end
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return nil
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end
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function FindKeyboard:find()
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local keyboards = {}
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for event_file_name in lfs.dir("/sys/class/input/") do
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if event_file_name:match("event.*") then
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local kb = self:check(event_file_name)
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if kb then
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table.insert(keyboards, kb)
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end
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end
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end
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return keyboards
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end
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return FindKeyboard
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