mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-23 20:53:53 +08:00
20375bf825
Simply added explanation from Al Viro in the following mail: http://lkml.indiana.edu/hypermail/linux/kernel/0802.2/3164.html Cc: Al Viro <viro@ftp.linux.org.uk> Cc: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
91 lines
3.1 KiB
Plaintext
91 lines
3.1 KiB
Plaintext
Copyright 2004 Linus Torvalds
|
|
Copyright 2004 Pavel Machek <pavel@suse.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.
|
|
|
|
|
|
Getting sparse
|
|
~~~~~~~~~~~~~~
|
|
|
|
You can get latest released versions from the Sparse homepage at
|
|
http://www.kernel.org/pub/linux/kernel/people/josh/sparse/
|
|
|
|
Alternatively, you can get snapshots of the latest development version
|
|
of sparse using git to clone..
|
|
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/josh/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.
|