afb3478162
When building with Clang + -Wtautological-constant-compare, several of
the ivtv and cx18 drivers warn along the lines of:
drivers/media/pci/cx18/cx18-driver.c:1005:21: warning: converting the
result of '<<' to a boolean always evaluates to true
[-Wtautological-constant-compare]
cx18_call_hw(cx, CX18_HW_GPIO_RESET_CTRL,
^
drivers/media/pci/cx18/cx18-cards.h:18:37: note: expanded from macro
'CX18_HW_GPIO_RESET_CTRL'
#define CX18_HW_GPIO_RESET_CTRL (1 << 6)
^
1 warning generated.
This warning happens because the shift operation is implicitly converted
to a boolean in v4l2_device_mask_call_all before being negated. This can
be solved by just comparing the mask result to 0 explicitly so that
there is no boolean conversion. The ultimate goal is to enable
-Wtautological-compare globally because there are several subwarnings
that would be helpful to have.
For visual consistency and avoidance of these warnings in the future,
all of the implicitly boolean conversions in the v4l2_device macros
are converted to explicit ones as well.
Link: https://github.com/ClangBuiltLinux/linux/issues/752
Reviewed-by: Ezequiel Garcia <ezequiel@collabora.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.