Speed up can327_is_valid_rx_char() with a LUT

diff --git a/module/can327.c b/module/can327.c
index 0ff377ab319710dd3b967ed8f4a951af7be869f0..aba198651476e1fe79f30ecdf4398e773e0d2c8d 100644 (file)
--- a/module/can327.c
+++ b/module/can327.c
@@ -896,20 +896,30 @@ static const struct net_device_ops can327_netdev_ops = {
        .ndo_change_mtu = can_change_mtu,
 };
 
-static bool can327_is_valid_rx_char(char c)
+static bool can327_is_valid_rx_char(u8 c)
 {
-       return (isdigit(c) ||
-               isupper(c) ||
-               c == ELM327_DUMMY_CHAR ||
-               c == ELM327_READY_CHAR ||
-               c == '<' ||
-               c == 'a' ||
-               c == 'b' ||
-               c == 'v' ||
-               c == '.' ||
-               c == '?' ||
-               c == '\r' ||
-               c == ' ');
+       static const bool lut_char_is_valid['z'] = {
+               ['\r'] = true,
+               [' '] = true,
+               ['.'] = true,
+               ['0'] = true, true, true, true, true,
+               ['5'] = true, true, true, true, true,
+               ['<'] = true,
+               [ELM327_READY_CHAR] = true,
+               ['?'] = true,
+               ['A'] = true, true, true, true, true, true, true,
+               ['H'] = true, true, true, true, true, true, true,
+               ['O'] = true, true, true, true, true, true, true,
+               ['V'] = true, true, true, true, true,
+               ['a'] = true,
+               ['b'] = true,
+               ['v'] = true,
+               [ELM327_DUMMY_CHAR] = true,
+       };
+       BUILD_BUG_ON(ELM327_DUMMY_CHAR >= 'z');
+
+       return (c < ARRAY_SIZE(lut_char_is_valid) &&
+               lut_char_is_valid[c]);
 }
 
 /* Handle incoming ELM327 ASCII data.