Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

Copyright 2004 Linus Torvalds

Copyright 2004 Pavel Machek 

Copyright 2006 Bob Copeland 

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.

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 CHECKFLAGS 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 CHECKFLAGS="-D__CHECK_ENDIAN__"

These checks are disabled by default as they generate a host of warnings.