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Based on kernel version 4.8. Page generated on 2016-10-06 23:19 EST.

1	Copyright 2004 Linus Torvalds
2	Copyright 2004 Pavel Machek <pavel@ucw.cz>
3	Copyright 2006 Bob Copeland <me@bobcopeland.com>
5	Using sparse for typechecking
6	~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
8	"__bitwise" is a type attribute, so you have to do something like this:
10	        typedef int __bitwise pm_request_t;
12	        enum pm_request {
13	                PM_SUSPEND = (__force pm_request_t) 1,
14	                PM_RESUME = (__force pm_request_t) 2
15	        };
17	which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is
18	there because sparse will complain about casting to/from a bitwise type,
19	but in this case we really _do_ want to force the conversion). And because
20	the enum values are all the same type, now "enum pm_request" will be that
21	type too.
23	And with gcc, all the __bitwise/__force stuff goes away, and it all ends
24	up looking just like integers to gcc.
26	Quite frankly, you don't need the enum there. The above all really just
27	boils down to one special "int __bitwise" type.
29	So the simpler way is to just do
31	        typedef int __bitwise pm_request_t;
33	        #define PM_SUSPEND ((__force pm_request_t) 1)
34	        #define PM_RESUME ((__force pm_request_t) 2)
36	and you now have all the infrastructure needed for strict typechecking.
38	One small note: the constant integer "0" is special. You can use a
39	constant zero as a bitwise integer type without sparse ever complaining.
40	This is because "bitwise" (as the name implies) was designed for making
41	sure that bitwise types don't get mixed up (little-endian vs big-endian
42	vs cpu-endian vs whatever), and there the constant "0" really _is_
43	special.
45	__bitwise__ - to be used for relatively compact stuff (gfp_t, etc.) that
46	is mostly warning-free and is supposed to stay that way.  Warnings will
47	be generated without __CHECK_ENDIAN__.
49	__bitwise - noisy stuff; in particular, __le*/__be* are that.  We really
50	don't want to drown in noise unless we'd explicitly asked for it.
52	Using sparse for lock checking
53	~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
55	The following macros are undefined for gcc and defined during a sparse
56	run to use the "context" tracking feature of sparse, applied to
57	locking.  These annotations tell sparse when a lock is held, with
58	regard to the annotated function's entry and exit.
60	__must_hold - The specified lock is held on function entry and exit.
62	__acquires - The specified lock is held on function exit, but not entry.
64	__releases - The specified lock is held on function entry, but not exit.
66	If the function enters and exits without the lock held, acquiring and
67	releasing the lock inside the function in a balanced way, no
68	annotation is needed.  The tree annotations above are for cases where
69	sparse would otherwise report a context imbalance.
71	Getting sparse
72	~~~~~~~~~~~~~~
74	You can get latest released versions from the Sparse homepage at
75	https://sparse.wiki.kernel.org/index.php/Main_Page
77	Alternatively, you can get snapshots of the latest development version
78	of sparse using git to clone..
80	        git://git.kernel.org/pub/scm/devel/sparse/sparse.git
82	DaveJ has hourly generated tarballs of the git tree available at..
84	        http://www.codemonkey.org.uk/projects/git-snapshots/sparse/
87	Once you have it, just do
89	        make
90	        make install
92	as a regular user, and it will install sparse in your ~/bin directory.
94	Using sparse
95	~~~~~~~~~~~~
97	Do a kernel make with "make C=1" to run sparse on all the C files that get
98	recompiled, or use "make C=2" to run sparse on the files whether they need to
99	be recompiled or not.  The latter is a fast way to check the whole tree if you
100	have already built it.
102	The optional make variable CF can be used to pass arguments to sparse.  The
103	build system passes -Wbitwise to sparse automatically.  To perform endianness
104	checks, you may define __CHECK_ENDIAN__:
106	        make C=2 CF="-D__CHECK_ENDIAN__"
108	These checks are disabled by default as they generate a host of warnings.
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