linux-kernel - [PATCH] ALSA: opti9xx: shut up gcc-10 range warning

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Message-Id: <20200429190216.85919-1-arnd@arndb.de>
Date:   Wed, 29 Apr 2020 21:02:03 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
Cc:     Arnd Bergmann <arnd@...db.de>, Takashi Iwai <tiwai@...e.de>,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: [PATCH] ALSA: opti9xx: shut up gcc-10 range warning

gcc-10 points out a few instances of suspicious integer arithmetic
leading to value truncation:

sound/isa/opti9xx/opti92x-ad1848.c: In function 'snd_opti9xx_configure':
sound/isa/opti9xx/opti92x-ad1848.c:322:43: error: overflow in conversion from 'int' to 'unsigned char' changes value from '(int)snd_opti9xx_read(chip, 3) & -256 | 240' to '240' [-Werror=overflow]
  322 |   (snd_opti9xx_read(chip, reg) & ~(mask)) | ((value) & (mask)))
      |   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
sound/isa/opti9xx/opti92x-ad1848.c:351:3: note: in expansion of macro 'snd_opti9xx_write_mask'
  351 |   snd_opti9xx_write_mask(chip, OPTi9XX_MC_REG(3), 0xf0, 0xff);
      |   ^~~~~~~~~~~~~~~~~~~~~~
sound/isa/opti9xx/miro.c: In function 'snd_miro_configure':
sound/isa/opti9xx/miro.c:873:40: error: overflow in conversion from 'int' to 'unsigned char' changes value from '(int)snd_miro_read(chip, 3) & -256 | 240' to '240' [-Werror=overflow]
  873 |   (snd_miro_read(chip, reg) & ~(mask)) | ((value) & (mask)))
      |   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
sound/isa/opti9xx/miro.c:1010:3: note: in expansion of macro 'snd_miro_write_mask'
 1010 |   snd_miro_write_mask(chip, OPTi9XX_MC_REG(3), 0xf0, 0xff);
      |   ^~~~~~~~~~~~~~~~~~~

These are all harmless here as only the low 8 bit are passed down
anyway. Change the macros to inline functions to make the code
more readable and also avoid the warning.

Strictly speaking those functions also need locking to make the
read/write pair atomic, but it seems unlikely that anyone would
still run into that issue.

Fixes: 1841f613fd2e ("[ALSA] Add snd-miro driver")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 sound/isa/opti9xx/miro.c           | 9 ++++++---
 sound/isa/opti9xx/opti92x-ad1848.c | 9 ++++++---
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/sound/isa/opti9xx/miro.c b/sound/isa/opti9xx/miro.c
index e764816a8f7a..b039429e6871 100644
--- a/sound/isa/opti9xx/miro.c
+++ b/sound/isa/opti9xx/miro.c
@@ -867,10 +867,13 @@ static void snd_miro_write(struct snd_miro *chip, unsigned char reg,
 	spin_unlock_irqrestore(&chip->lock, flags);
 }
 
+static inline void snd_miro_write_mask(struct snd_miro *chip,
+		unsigned char reg, unsigned char value, unsigned char mask)
+{
+	unsigned char oldval = snd_miro_read(chip, reg);
 
-#define snd_miro_write_mask(chip, reg, value, mask)	\
-	snd_miro_write(chip, reg,			\
-		(snd_miro_read(chip, reg) & ~(mask)) | ((value) & (mask)))
+	snd_miro_write(chip, reg, (oldval & ~mask) | (value & mask));
+}
 
 /*
  *  Proc Interface
diff --git a/sound/isa/opti9xx/opti92x-ad1848.c b/sound/isa/opti9xx/opti92x-ad1848.c
index d06b29693c85..0e6d20e49158 100644
--- a/sound/isa/opti9xx/opti92x-ad1848.c
+++ b/sound/isa/opti9xx/opti92x-ad1848.c
@@ -317,10 +317,13 @@ static void snd_opti9xx_write(struct snd_opti9xx *chip, unsigned char reg,
 }
 
 
-#define snd_opti9xx_write_mask(chip, reg, value, mask)	\
-	snd_opti9xx_write(chip, reg,			\
-		(snd_opti9xx_read(chip, reg) & ~(mask)) | ((value) & (mask)))
+static inline void snd_opti9xx_write_mask(struct snd_opti9xx *chip,
+		unsigned char reg, unsigned char value, unsigned char mask)
+{
+	unsigned char oldval = snd_opti9xx_read(chip, reg);
 
+	snd_opti9xx_write(chip, reg, (oldval & ~mask) | (value & mask));
+}
 
 static int snd_opti9xx_configure(struct snd_opti9xx *chip,
 					   long port,
-- 
2.26.0