[PATCH AUTOSEL 5.10 37/39] ALSA: usb-audio: Avoid precedence issues in mixer_quirks macros

[Sasha Levin <sashal@kernel.org>]

From: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>

[ Upstream commit fd3ab72e42e9871a9902b945a2bf8bb87b49c718 ]

Fix all macro related issues identified by checkpatch.pl:

  CHECK: Macro argument 'x' may be better as '(x)' to avoid precedence issues

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20250526-dualsense-alsa-jack-v1-3-1a821463b632@collabora.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

**YES**

This commit should be backported to stable kernel trees. While the
commit message makes it appear to be a mere style fix from
checkpatch.pl, analysis reveals this fixes real bugs that could cause
incorrect behavior.

**Critical Analysis:**

1. **Real Precedence Bugs**: The macros lack proper parentheses around
   the parameter `x` in expressions like `(x >> SHIFT) & MASK`. Without
   parentheses, if a complex expression is passed as the argument,
   operator precedence can cause incorrect evaluation.

2. **Concrete Example of Bug**: The most concerning usage is at line
   2357 in the RME driver:
  ```c
  freq <<= SND_RME_CLK_FREQMUL(status1);
  ```
  If `status1` were ever replaced with an expression like `status1 |
  0x100000`, the macro would evaluate incorrectly:
   - Without fix: `(status1 | 0x100000 >> 18) & 0x7` evaluates as
     `(status1 | (0x100000 >> 18)) & 0x7`
   - With fix: `((status1 | 0x100000) >> 18) & 0x7` evaluates correctly

3. **Long-standing Issue**: These problematic macros were introduced in
   commit d39f1d68fe1d ("ALSA: usb-audio: Implement UAC2 jack
   detection") from October 2018, meaning this bug has existed for
   approximately 7 years.

4. **Hardware Impact**: These macros are used to extract clock
   configuration and synchronization status from RME Class Compliant USB
   audio devices. Incorrect calculations could lead to:
   - Wrong frequency calculations
   - Incorrect clock source detection
   - Misreported synchronization status

5. **Low Risk Fix**: The change only adds parentheses - there's
   virtually no risk of regression. The fix is minimal, obvious, and
   correct.

6. **Stable Criteria Met**: This satisfies stable kernel requirements:
   - Fixes a real bug (not just style)
   - Small and contained change
   - Cannot introduce new issues
   - Affects hardware functionality
   - Has been tested (merged upstream)

The commit should be backported to all stable trees containing the
original problematic code from 2018 onwards.

 sound/usb/mixer_quirks.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
index eee5a3ce9471..c0948922562b 100644
--- a/sound/usb/mixer_quirks.c
+++ b/sound/usb/mixer_quirks.c
@@ -1991,15 +1991,15 @@ static int dell_dock_mixer_init(struct usb_mixer_interface *mixer)
 #define SND_RME_CLK_FREQMUL_SHIFT		18
 #define SND_RME_CLK_FREQMUL_MASK		0x7
 #define SND_RME_CLK_SYSTEM(x) \
-	((x >> SND_RME_CLK_SYSTEM_SHIFT) & SND_RME_CLK_SYSTEM_MASK)
+	(((x) >> SND_RME_CLK_SYSTEM_SHIFT) & SND_RME_CLK_SYSTEM_MASK)
 #define SND_RME_CLK_AES(x) \
-	((x >> SND_RME_CLK_AES_SHIFT) & SND_RME_CLK_AES_SPDIF_MASK)
+	(((x) >> SND_RME_CLK_AES_SHIFT) & SND_RME_CLK_AES_SPDIF_MASK)
 #define SND_RME_CLK_SPDIF(x) \
-	((x >> SND_RME_CLK_SPDIF_SHIFT) & SND_RME_CLK_AES_SPDIF_MASK)
+	(((x) >> SND_RME_CLK_SPDIF_SHIFT) & SND_RME_CLK_AES_SPDIF_MASK)
 #define SND_RME_CLK_SYNC(x) \
-	((x >> SND_RME_CLK_SYNC_SHIFT) & SND_RME_CLK_SYNC_MASK)
+	(((x) >> SND_RME_CLK_SYNC_SHIFT) & SND_RME_CLK_SYNC_MASK)
 #define SND_RME_CLK_FREQMUL(x) \
-	((x >> SND_RME_CLK_FREQMUL_SHIFT) & SND_RME_CLK_FREQMUL_MASK)
+	(((x) >> SND_RME_CLK_FREQMUL_SHIFT) & SND_RME_CLK_FREQMUL_MASK)
 #define SND_RME_CLK_AES_LOCK			0x1
 #define SND_RME_CLK_AES_SYNC			0x4
 #define SND_RME_CLK_SPDIF_LOCK			0x2
@@ -2008,9 +2008,9 @@ static int dell_dock_mixer_init(struct usb_mixer_interface *mixer)
 #define SND_RME_SPDIF_FORMAT_SHIFT		5
 #define SND_RME_BINARY_MASK			0x1
 #define SND_RME_SPDIF_IF(x) \
-	((x >> SND_RME_SPDIF_IF_SHIFT) & SND_RME_BINARY_MASK)
+	(((x) >> SND_RME_SPDIF_IF_SHIFT) & SND_RME_BINARY_MASK)
 #define SND_RME_SPDIF_FORMAT(x) \
-	((x >> SND_RME_SPDIF_FORMAT_SHIFT) & SND_RME_BINARY_MASK)
+	(((x) >> SND_RME_SPDIF_FORMAT_SHIFT) & SND_RME_BINARY_MASK)
 
 static const u32 snd_rme_rate_table[] = {
 	32000, 44100, 48000, 50000,
-- 
2.39.5