Revision e7e11d8ba807d451857b5c68abe249c7fc2b980f authored by Alexander Stein on 29 May 2012, 22:07:30 UTC, committed by Linus Torvalds on 29 May 2012, 23:22:32 UTC
When issuing the following command: for I in 0 1 2 3 4 5 6 7; do echo 0 > /sys/class/leds/pca955x\:${I}/brightness; done It is possible that all the pca955x_read_ls calls are done sequentially before any pca955x_write_ls call is done. This updates the LS only to the last LED update in its set. Fix this by using a global lock for the pca995x device during pca955x_led_work. Also used a struct for shared data betreen all LEDs. [akpm@linux-foundation.org: revert unintentional rename of pca955x_ledsel()] Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com> Cc: Richard Purdie <rpurdie@rpsys.net> Cc: Bryan Wu <bryan.wu@canonical.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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sparse.txt
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.
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.
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