--- /dev/null
+.. Copyright 2004 Linus Torvalds
+.. Copyright 2004 Pavel Machek <pavel@ucw.cz>
+.. Copyright 2006 Bob Copeland <me@bobcopeland.com>
+
+Sparse
+======
+
+Sparse is a semantic checker for C programs; it can be used to find a
+number of potential problems with kernel code. See
+https://lwn.net/Articles/689907/ for an overview of sparse; this document
+contains some kernel-specific sparse information.
+
+
+Using sparse for typechecking
+-----------------------------
+
+"__bitwise" is a type attribute, so you have to do something like this::
+
+ typedef int __bitwise pm_request_t;
+
+ enum pm_request {
+ PM_SUSPEND = (__force pm_request_t) 1,
+ PM_RESUME = (__force pm_request_t) 2
+ };
+
+which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is
+there because sparse will complain about casting to/from a bitwise type,
+but in this case we really _do_ want to force the conversion). And because
+the enum values are all the same type, now "enum pm_request" will be that
+type too.
+
+And with gcc, all the "__bitwise"/"__force stuff" goes away, and it all
+ends up looking just like integers to gcc.
+
+Quite frankly, you don't need the enum there. The above all really just
+boils down to one special "int __bitwise" type.
+
+So the simpler way is to just do::
+
+ typedef int __bitwise pm_request_t;
+
+ #define PM_SUSPEND ((__force pm_request_t) 1)
+ #define PM_RESUME ((__force pm_request_t) 2)
+
+and you now have all the infrastructure needed for strict typechecking.
+
+One small note: the constant integer "0" is special. You can use a
+constant zero as a bitwise integer type without sparse ever complaining.
+This is because "bitwise" (as the name implies) was designed for making
+sure that bitwise types don't get mixed up (little-endian vs big-endian
+vs cpu-endian vs whatever), and there the constant "0" really _is_
+special.
+
+__bitwise__ - to be used for relatively compact stuff (gfp_t, etc.) that
+is mostly warning-free and is supposed to stay that way. Warnings will
+be generated without __CHECK_ENDIAN__.
+
+__bitwise - noisy stuff; in particular, __le*/__be* are that. We really
+don't want to drown in noise unless we'd explicitly asked for it.
+
+Using sparse for lock checking
+------------------------------
+
+The following macros are undefined for gcc and defined during a sparse
+run to use the "context" tracking feature of sparse, applied to
+locking. These annotations tell sparse when a lock is held, with
+regard to the annotated function's entry and exit.
+
+__must_hold - The specified lock is held on function entry and exit.
+
+__acquires - The specified lock is held on function exit, but not entry.
+
+__releases - The specified lock is held on function entry, but not exit.
+
+If the function enters and exits without the lock held, acquiring and
+releasing the lock inside the function in a balanced way, no
+annotation is needed. The tree annotations above are for cases where
+sparse would otherwise report a context imbalance.
+
+Getting sparse
+--------------
+
+You can get latest released versions from the Sparse homepage at
+https://sparse.wiki.kernel.org/index.php/Main_Page
+
+Alternatively, you can get snapshots of the latest development version
+of sparse using git to clone::
+
+ git://git.kernel.org/pub/scm/devel/sparse/sparse.git
+
+DaveJ has hourly generated tarballs of the git tree available at::
+
+ http://www.codemonkey.org.uk/projects/git-snapshots/sparse/
+
+
+Once you have it, just do::
+
+ make
+ make install
+
+as a regular user, and it will install sparse in your ~/bin directory.
+
+Using sparse
+------------
+
+Do a kernel make with "make C=1" to run sparse on all the C files that get
+recompiled, or use "make C=2" to run sparse on the files whether they need to
+be recompiled or not. The latter is a fast way to check the whole tree if you
+have already built it.
+
+The optional make variable CF can be used to pass arguments to sparse. The
+build system passes -Wbitwise to sparse automatically. To perform endianness
+checks, you may define __CHECK_ENDIAN__::
+
+ make C=2 CF="-D__CHECK_ENDIAN__"
+
+These checks are disabled by default as they generate a host of warnings.
+++ /dev/null
-Copyright 2004 Linus Torvalds
-Copyright 2004 Pavel Machek <pavel@ucw.cz>
-Copyright 2006 Bob Copeland <me@bobcopeland.com>
-
-Using sparse for typechecking
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-"__bitwise" is a type attribute, so you have to do something like this:
-
- typedef int __bitwise pm_request_t;
-
- enum pm_request {
- PM_SUSPEND = (__force pm_request_t) 1,
- PM_RESUME = (__force pm_request_t) 2
- };
-
-which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is
-there because sparse will complain about casting to/from a bitwise type,
-but in this case we really _do_ want to force the conversion). And because
-the enum values are all the same type, now "enum pm_request" will be that
-type too.
-
-And with gcc, all the __bitwise/__force stuff goes away, and it all ends
-up looking just like integers to gcc.
-
-Quite frankly, you don't need the enum there. The above all really just
-boils down to one special "int __bitwise" type.
-
-So the simpler way is to just do
-
- typedef int __bitwise pm_request_t;
-
- #define PM_SUSPEND ((__force pm_request_t) 1)
- #define PM_RESUME ((__force pm_request_t) 2)
-
-and you now have all the infrastructure needed for strict typechecking.
-
-One small note: the constant integer "0" is special. You can use a
-constant zero as a bitwise integer type without sparse ever complaining.
-This is because "bitwise" (as the name implies) was designed for making
-sure that bitwise types don't get mixed up (little-endian vs big-endian
-vs cpu-endian vs whatever), and there the constant "0" really _is_
-special.
-
-__bitwise__ - to be used for relatively compact stuff (gfp_t, etc.) that
-is mostly warning-free and is supposed to stay that way. Warnings will
-be generated without __CHECK_ENDIAN__.
-
-__bitwise - noisy stuff; in particular, __le*/__be* are that. We really
-don't want to drown in noise unless we'd explicitly asked for it.
-
-Using sparse for lock checking
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The following macros are undefined for gcc and defined during a sparse
-run to use the "context" tracking feature of sparse, applied to
-locking. These annotations tell sparse when a lock is held, with
-regard to the annotated function's entry and exit.
-
-__must_hold - The specified lock is held on function entry and exit.
-
-__acquires - The specified lock is held on function exit, but not entry.
-
-__releases - The specified lock is held on function entry, but not exit.
-
-If the function enters and exits without the lock held, acquiring and
-releasing the lock inside the function in a balanced way, no
-annotation is needed. The tree annotations above are for cases where
-sparse would otherwise report a context imbalance.
-
-Getting sparse
-~~~~~~~~~~~~~~
-
-You can get latest released versions from the Sparse homepage at
-https://sparse.wiki.kernel.org/index.php/Main_Page
-
-Alternatively, you can get snapshots of the latest development version
-of sparse using git to clone..
-
- git://git.kernel.org/pub/scm/devel/sparse/sparse.git
-
-DaveJ has hourly generated tarballs of the git tree available at..
-
- http://www.codemonkey.org.uk/projects/git-snapshots/sparse/
-
-
-Once you have it, just do
-
- make
- make install
-
-as a regular user, and it will install sparse in your ~/bin directory.
-
-Using sparse
-~~~~~~~~~~~~
-
-Do a kernel make with "make C=1" to run sparse on all the C files that get
-recompiled, or use "make C=2" to run sparse on the files whether they need to
-be recompiled or not. The latter is a fast way to check the whole tree if you
-have already built it.
-
-The optional make variable CF can be used to pass arguments to sparse. The
-build system passes -Wbitwise to sparse automatically. To perform endianness
-checks, you may define __CHECK_ENDIAN__:
-
- make C=2 CF="-D__CHECK_ENDIAN__"
-
-These checks are disabled by default as they generate a host of warnings.
projects / cascardo / linux.git / commitdiff