netdev - [PATCH net-next v1 2/2] ethtool: refactor bit-shifts

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Message-Id: <20221207231728.2331166-3-jesse.brandeburg@intel.com>
Date:   Wed,  7 Dec 2022 15:17:28 -0800
From:   Jesse Brandeburg <jesse.brandeburg@...el.com>
To:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com
Cc:     netdev@...r.kernel.org, mkubecek@...e.cz,
        Jesse Brandeburg <jesse.brandeburg@...el.com>
Subject: [PATCH net-next v1 2/2] ethtool: refactor bit-shifts

While coding up the BIT() conversions for ethtool, some ugly conversions
and code were noticed and we can fix them with a little GENMASK and a
small refactor to use local variables to simplify some bitset.c code.

These changes should have no functional effect.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@...el.com>
---
 net/ethtool/bitset.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/net/ethtool/bitset.c b/net/ethtool/bitset.c
index 0515d6604b3b..ac289f335582 100644
--- a/net/ethtool/bitset.c
+++ b/net/ethtool/bitset.c
@@ -14,12 +14,12 @@
 
 static u32 ethnl_lower_bits(unsigned int n)
 {
-	return ~(u32)0 >> (32 - n % 32);
+	return GENMASK((n % 32), 0);
 }
 
 static u32 ethnl_upper_bits(unsigned int n)
 {
-	return ~(u32)0 << (n % 32);
+	return GENMASK(31, (n % 32));
 }
 
 /**
@@ -452,8 +452,8 @@ ethnl_update_bitset32_verbose(u32 *bitmap, unsigned int nbits,
 		ethnl_bitmap32_clear(bitmap, 0, nbits, mod);
 
 	nla_for_each_nested(bit_attr, tb[ETHTOOL_A_BITSET_BITS], rem) {
+		unsigned int idx, bitmap_idx, mod_idx;
 		bool old_val, new_val;
-		unsigned int idx;
 
 		if (nla_type(bit_attr) != ETHTOOL_A_BITSET_BITS_BIT) {
 			NL_SET_ERR_MSG_ATTR(extack, bit_attr,
@@ -464,12 +464,14 @@ ethnl_update_bitset32_verbose(u32 *bitmap, unsigned int nbits,
 				      names, extack);
 		if (ret < 0)
 			return ret;
-		old_val = bitmap[idx / 32] & ((u32)1 << (idx % 32));
+		bitmap_idx = idx / 32;
+		mod_idx = idx % 32;
+		old_val = bitmap[bitmap_idx] & BIT(mod_idx);
 		if (new_val != old_val) {
 			if (new_val)
-				bitmap[idx / 32] |= ((u32)1 << (idx % 32));
+				bitmap[bitmap_idx] |= BIT(mod_idx);
 			else
-				bitmap[idx / 32] &= ~((u32)1 << (idx % 32));
+				bitmap[bitmap_idx] &= ~BIT(mod_idx);
 			*mod = true;
 		}
 	}
-- 
2.31.1