[alsa-devel] Applied "ASoC: hdmi-codec: use unsigned type to structure members with bit-field" to the asoc tree

[Mark Brown]

The patch

   ASoC: hdmi-codec: use unsigned type to structure members with bit-field

has been applied to the asoc tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From 9e4d59ada4d602e78eee9fb5f898ce61fdddb446 Mon Sep 17 00:00:00 2001
From: Takashi Sakamoto <o-takashi at sakamocchi.jp>
Date: Fri, 16 Dec 2016 18:26:54 +0900
Subject: [PATCH] ASoC: hdmi-codec: use unsigned type to structure members with
 bit-field

This is a fix for Linux 4.10-rc1.

In C language specification, a bit-field is interpreted as a signed or
unsigned integer type consisting of the specified number of bits.

In GCC manual, the range of a signed bit field of N bits is from
-(2^N) / 2 to ((2^N) / 2) - 1
https://www.gnu.org/software/gnu-c-manual/gnu-c-manual.html#Bit-Fields

Therefore, when defined as 1 bit-field with signed type, variables can
represents -1 and 0.

The snd-soc-hdmi-codec module includes a structure which has signed type
members with bit-fields. Codes of this module assign 0 and 1 to the
members. This seems to result in implementation-dependent behaviours.

As of v4.10-rc1 merge window, outside of sound subsystem, this structure
is referred by below GPU modules.
 - tda998x
 - sti-drm
 - mediatek-drm-hdmi
 - msm

As long as I review their codes relevant to the structure, the structure
members are used just for condition statements and printk formats.
My proposal of change is a bit intrusive to the printk formats but this
may be acceptable.

Totally, it's reasonable to use unsigned type for the structure members.
This bug is detected by Sparse, static code analyzer with below warnings.

./include/sound/hdmi-codec.h:39:26: error: dubious one-bit signed bitfield
./include/sound/hdmi-codec.h:40:28: error: dubious one-bit signed bitfield
./include/sound/hdmi-codec.h:41:29: error: dubious one-bit signed bitfield
./include/sound/hdmi-codec.h:42:31: error: dubious one-bit signed bitfield

Fixes: 09184118a8ab ("ASoC: hdmi-codec: Add hdmi-codec for external HDMI-encoders")
Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
Acked-by: Arnaud Pouliquen <arnaud.pouliquen at st.com>
Signed-off-by: Mark Brown <broonie at kernel.org>
CC: stable at vger.kernel.org
---
 include/sound/hdmi-codec.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/sound/hdmi-codec.h b/include/sound/hdmi-codec.h
index 530c57bdefa0..915c4357945c 100644
--- a/include/sound/hdmi-codec.h
+++ b/include/sound/hdmi-codec.h
@@ -36,10 +36,10 @@ struct hdmi_codec_daifmt {
 		HDMI_AC97,
 		HDMI_SPDIF,
 	} fmt;
-	int bit_clk_inv:1;
-	int frame_clk_inv:1;
-	int bit_clk_master:1;
-	int frame_clk_master:1;
+	unsigned int bit_clk_inv:1;
+	unsigned int frame_clk_inv:1;
+	unsigned int bit_clk_master:1;
+	unsigned int frame_clk_master:1;
 };
 
 /*
-- 
2.11.0