From mboxrd@z Thu Jan  1 00:00:00 1970
From: Claude Code Review Bot <claude-review@example.com>
To: dri-devel-reviews@example.com
Subject: Claude review: video: fbdev: sm712: Fix operator precedence in big_swap macro
Date: Sat, 16 May 2026 10:14:54 +1000
Message-ID: <review-patch1-20260515010202.2506-1-lirongqing@baidu.com>
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References: <20260515010202.2506-1-lirongqing@baidu.com> <20260515010202.2506-1-lirongqing@baidu.com>
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Patch Review

**Status: Correct fix for a real bug.**

The commit message clearly explains the problem: C operator precedence mean=
s `<<` and `>>` bind tighter than `&`, so the original code:

```c
#define big_swap(p)		((p & 0xff00ff00 >> 8) | (p & 0x00ff00ff << 8))
```

was parsed as:

```c
((p & (0xff00ff00 >> 8)) | (p & (0x00ff00ff << 8)))
```

which is `((p & 0x00ff00ff) | (p & 0xff00ff00))` =E2=80=94 effectively just=
 `p` (identity), completely defeating the byte swap.

The fix:

```c
#define big_swap(p)		(((p & 0xff00ff00) >> 8) | ((p & 0x00ff00ff) << 8))
```

correctly masks first, then shifts, implementing a proper swap of the high =
and low bytes within each 16-bit half of a 32-bit value.

**Verification:** All three call sites in `sm712fb.c` (lines 1010, 1069, 11=
41) use this for big-endian palette and framebuffer operations. The fix res=
tores the intended byte-swap behavior that has been broken since the origin=
al merge.

**Nit (not blocking):** The macro argument `p` is not wrapped in parenthese=
s (e.g., `(p)`) to guard against complex expressions. Since all current cal=
lers pass simple lvalues, this is a pre-existing cosmetic issue and not wor=
th blocking the fix.

**Verdict: Reviewed-by worthy.** The Fixes tag correctly identifies the ori=
ginating commit, and the fix is minimal and correct.

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