| Message ID | 20161216092654.7773-1-o-takashi@sakamocchi.jp (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Oops. This is not a patch for alsa-lib, but for Linux kernel. I'm sorry to confuse you... On Dec 16 2016 18:26, Takashi Sakamoto wrote: > 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 > > CC: Jyri Sarha <jsarha@ti.com> > CC: Jie Qiu <jie.qiu@mediatek.com> > CC: Arnaud Pouliquen <arnaud.pouliquen@st.com> > CC: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> > CC: dri-devel@lists.freedesktop.org > CC: stable@vger.kernel.org > Fixes: 09184118a8ab ("ASoC: hdmi-codec: Add hdmi-codec for external HDMI-encoders") > Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> > --- > 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 530c57b..915c435 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; > }; > > /* Regards Takashi Sakamoto
diff --git a/include/sound/hdmi-codec.h b/include/sound/hdmi-codec.h index 530c57b..915c435 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; }; /*
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 CC: Jyri Sarha <jsarha@ti.com> CC: Jie Qiu <jie.qiu@mediatek.com> CC: Arnaud Pouliquen <arnaud.pouliquen@st.com> CC: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> CC: dri-devel@lists.freedesktop.org CC: stable@vger.kernel.org Fixes: 09184118a8ab ("ASoC: hdmi-codec: Add hdmi-codec for external HDMI-encoders") Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> --- include/sound/hdmi-codec.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)