Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst
index 4e7c0a1..ada573b 100644
--- a/Documentation/process/coding-style.rst
+++ b/Documentation/process/coding-style.rst
@@ -56,7 +56,7 @@
case 'K':
case 'k':
mem <<= 10;
- /* fall through */
+ fallthrough;
default:
break;
}
@@ -443,6 +443,9 @@
Although this is not required by the C language, it is preferred in Linux
because it is a simple way to add valuable information for the reader.
+Do not use the ``extern`` keyword with function prototypes as this makes
+lines longer and isn't strictly necessary.
+
7) Centralized exiting of functions
-----------------------------------
@@ -592,26 +595,43 @@
(* (max steps 1)
c-basic-offset)))
- (add-hook 'c-mode-common-hook
- (lambda ()
- ;; Add kernel style
- (c-add-style
- "linux-tabs-only"
- '("linux" (c-offsets-alist
- (arglist-cont-nonempty
- c-lineup-gcc-asm-reg
- c-lineup-arglist-tabs-only))))))
+ (dir-locals-set-class-variables
+ 'linux-kernel
+ '((c-mode . (
+ (c-basic-offset . 8)
+ (c-label-minimum-indentation . 0)
+ (c-offsets-alist . (
+ (arglist-close . c-lineup-arglist-tabs-only)
+ (arglist-cont-nonempty .
+ (c-lineup-gcc-asm-reg c-lineup-arglist-tabs-only))
+ (arglist-intro . +)
+ (brace-list-intro . +)
+ (c . c-lineup-C-comments)
+ (case-label . 0)
+ (comment-intro . c-lineup-comment)
+ (cpp-define-intro . +)
+ (cpp-macro . -1000)
+ (cpp-macro-cont . +)
+ (defun-block-intro . +)
+ (else-clause . 0)
+ (func-decl-cont . +)
+ (inclass . +)
+ (inher-cont . c-lineup-multi-inher)
+ (knr-argdecl-intro . 0)
+ (label . -1000)
+ (statement . 0)
+ (statement-block-intro . +)
+ (statement-case-intro . +)
+ (statement-cont . +)
+ (substatement . +)
+ ))
+ (indent-tabs-mode . t)
+ (show-trailing-whitespace . t)
+ ))))
- (add-hook 'c-mode-hook
- (lambda ()
- (let ((filename (buffer-file-name)))
- ;; Enable kernel mode for the appropriate files
- (when (and filename
- (string-match (expand-file-name "~/src/linux-trees")
- filename))
- (setq indent-tabs-mode t)
- (setq show-trailing-whitespace t)
- (c-set-style "linux-tabs-only")))))
+ (dir-locals-set-directory-class
+ (expand-file-name "~/src/linux-trees")
+ 'linux-kernel)
This will make emacs go better with the kernel coding style for C
files below ``~/src/linux-trees``.
@@ -666,7 +686,7 @@
...
For full documentation on the configuration files, see the file
-Documentation/kbuild/kconfig-language.txt.
+Documentation/kbuild/kconfig-language.rst.
11) Data structures
@@ -823,7 +843,8 @@
The kernel provides the following general purpose memory allocators:
kmalloc(), kzalloc(), kmalloc_array(), kcalloc(), vmalloc(), and
vzalloc(). Please refer to the API documentation for further information
-about them.
+about them. :ref:`Documentation/core-api/memory-allocation.rst
+<memory_allocation>`
The preferred form for passing a size of a struct is the following:
@@ -854,6 +875,9 @@
Both forms check for overflow on the allocation size n * sizeof(...),
and return NULL if that occurred.
+These generic allocation functions all emit a stack dump on failure when used
+without __GFP_NOWARN so there is no use in emitting an additional failure
+message when NULL is returned.
15) The inline disease
----------------------
@@ -918,7 +942,37 @@
NULL or the ERR_PTR mechanism to report failure.
-17) Don't re-invent the kernel macros
+17) Using bool
+--------------
+
+The Linux kernel bool type is an alias for the C99 _Bool type. bool values can
+only evaluate to 0 or 1, and implicit or explicit conversion to bool
+automatically converts the value to true or false. When using bool types the
+!! construction is not needed, which eliminates a class of bugs.
+
+When working with bool values the true and false definitions should be used
+instead of 1 and 0.
+
+bool function return types and stack variables are always fine to use whenever
+appropriate. Use of bool is encouraged to improve readability and is often a
+better option than 'int' for storing boolean values.
+
+Do not use bool if cache line layout or size of the value matters, as its size
+and alignment varies based on the compiled architecture. Structures that are
+optimized for alignment and size should not use bool.
+
+If a structure has many true/false values, consider consolidating them into a
+bitfield with 1 bit members, or using an appropriate fixed width type, such as
+u8.
+
+Similarly for function arguments, many true/false values can be consolidated
+into a single bitwise 'flags' argument and 'flags' can often be a more
+readable alternative if the call-sites have naked true/false constants.
+
+Otherwise limited use of bool in structures and arguments can improve
+readability.
+
+18) Don't re-invent the kernel macros
-------------------------------------
The header file include/linux/kernel.h contains a number of macros that
@@ -941,7 +995,7 @@
defined that you shouldn't reproduce in your code.
-18) Editor modelines and other cruft
+19) Editor modelines and other cruft
------------------------------------
Some editors can interpret configuration information embedded in source files,
@@ -975,7 +1029,7 @@
work correctly.
-19) Inline assembly
+20) Inline assembly
-------------------
In architecture-specific code, you may need to use inline assembly to interface
@@ -1007,7 +1061,7 @@
: /* outputs */ : /* inputs */ : /* clobbers */);
-20) Conditional Compilation
+21) Conditional Compilation
---------------------------
Wherever possible, don't use preprocessor conditionals (#if, #ifdef) in .c
@@ -1075,5 +1129,5 @@
WG14 is the international standardization working group for the programming
language C, URL: http://www.open-std.org/JTC1/SC22/WG14/
-Kernel process/coding-style.rst, by greg@kroah.com at OLS 2002:
+Kernel :ref:`process/coding-style.rst <codingstyle>`, by greg@kroah.com at OLS 2002:
http://www.kroah.com/linux/talks/ols_2002_kernel_codingstyle_talk/html/