linux-kernel - [PATCH v6 2/2] staging: rtl8723bs: Use % 4096u instead of & 0xfff

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Message-Id: <27ff98a2d721a19cb09ea5c0d39c7d1616f8a629.1744061673.git.abrahamadekunle50@gmail.com>
Date: Mon,  7 Apr 2025 21:53:52 +0000
From: Abraham Samuel Adekunle <abrahamadekunle50@...il.com>
To: outreachy@...ts.linux.dev,
	gregkh@...uxfoundation.org,
	julia.lawall@...ia.fr
Cc: linux-staging@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	david.laight.linux@...il.com,
	andy@...nel.org,
	dan.carpenter@...aro.org,
	Abraham Samuel Adekunle <abrahamadekunle50@...il.com>
Subject: [PATCH v6 2/2] staging: rtl8723bs: Use % 4096u instead of & 0xfff

The sequence number is constrained to a range of [0, 4095], which
is a total of 4096 values. The bitmask operation using `& 0xfff` is
used to perform this wrap-around. While this is functionally correct,
it obscures the intended semantic of a 4096-based wrap.

Using a modulo operation `% 4096u` makes the wrap-around logic
explicit and easier to understand. It clearly signals that the
sequence number cycles through a range of 4096 values.
It also makes the code robust against potential changes of the 4096
upper limit, especially when it becomes a non power of 2 value while
the AND(&) works solely for power of 2 values.

The use of `% 4096u` also guarantees that the modulo operation is
performed with unsigned arithmetic, preventing potential issues with
the signed types.

Suggested-by: Andy Shevchenko <andy@...nel.org>
Suggested-by: David Laight <david.laight.linux@...il.com>
Signed-off-by: Abraham Samuel Adekunle <abrahamadekunle50@...il.com>
---
 drivers/staging/rtl8723bs/core/rtw_xmit.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/rtl8723bs/core/rtw_xmit.c b/drivers/staging/rtl8723bs/core/rtw_xmit.c
index c41de6fd897b..5cfb6d1e9dae 100644
--- a/drivers/staging/rtl8723bs/core/rtw_xmit.c
+++ b/drivers/staging/rtl8723bs/core/rtw_xmit.c
@@ -943,7 +943,7 @@ s32 rtw_make_wlanhdr(struct adapter *padapter, u8 *hdr, struct pkt_attrib *pattr
 
 			if (psta) {
 				psta->sta_xmitpriv.txseq_tid[pattrib->priority]++;
-				psta->sta_xmitpriv.txseq_tid[pattrib->priority] &= 0xFFF;
+				psta->sta_xmitpriv.txseq_tid[pattrib->priority] %= 4096u;
 				pattrib->seqnum = psta->sta_xmitpriv.txseq_tid[pattrib->priority];
 
 				SetSeqNum(hdr, pattrib->seqnum);
@@ -963,11 +963,11 @@ s32 rtw_make_wlanhdr(struct adapter *padapter, u8 *hdr, struct pkt_attrib *pattr
 					if (SN_LESS(pattrib->seqnum, tx_seq)) {
 						pattrib->ampdu_en = false;/* AGG BK */
 					} else if (SN_EQUAL(pattrib->seqnum, tx_seq)) {
-						psta->BA_starting_seqctrl[pattrib->priority & 0x0f] = (tx_seq + 1) & 0xfff;
+						psta->BA_starting_seqctrl[pattrib->priority & 0x0f] = (tx_seq + 1) % 4096u;
 
 						pattrib->ampdu_en = true;/* AGG EN */
 					} else {
-						psta->BA_starting_seqctrl[pattrib->priority & 0x0f] = (pattrib->seqnum + 1) & 0xfff;
+						psta->BA_starting_seqctrl[pattrib->priority & 0x0f] = (pattrib->seqnum + 1) % 4096u;
 						pattrib->ampdu_en = true;/* AGG EN */
 					}
 				}
-- 
2.34.1