docs: add sparse howto

docs: add sparse howto

[Pavel Machek]

Hi!

Installing / using sparse is not exactly trivial, this should make
setting it up easier. Please apply, 
								Pavel

Adapted From: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Pavel Machek <pavel@suse.cz>

--- clean/Documentation/sparse.txt	2004-10-16 23:48:08.000000000 +0200
+++ linux/Documentation/sparse.txt	2004-10-24 22:44:47.000000000 +0200
@@ -0,0 +1,72 @@
+Copyright 2004 Linus Torvalds
+Copyright 2004 Pavel Machek <pavel@suse.cz>
+
+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.
+
+Modify top-level Makefile to say
+
+CHECK           = sparse -Wbitwise
+
+or you don't get any checking at all.
+
+
+Where to get sparse
+~~~~~~~~~~~~~~~~~~~
+
+With BK, you can just get it from
+
+        bk://sparse.bkbits.net/sparse
+
+and DaveJ has tar-balls at
+
+	http://www.codemonkey.org.uk/projects/bitkeeper/sparse/
+
+
+Once you have it, just do
+
+        make
+        make install
+
+as your regular user, and it will install sparse in your ~/bin directory.
+After that, doing a kernel make with "make C=1" will run sparse on all the
+C files that get recompiled, or with "make C=2" will run sparse on the
+files whether they need to be recompiled or not (ie the latter is fast way
+to check the whole tree if you have already built it).

-- 
People were complaining that M$ turns users into beta-testers...
...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!

Re: docs: add sparse howto

[Jesper Juhl]

On Sat, 25 Dec 2004, Pavel Machek wrote:

> Hi!
> 
> Installing / using sparse is not exactly trivial, this should make
> setting it up easier. Please apply, 
> 								Pavel

/If/ that patch gets accepted may I suggest this companion?   :)

Add sparse.txt to Documentation/00-INDEX

Signed-off-by: Jesper Juhl <juhl-lkml@dif.dk>

diff -u linux-2.6.10-rc3-bk16-orig/Documentation/00-INDEX linux-2.6.10-rc3-bk16/Documentation/00-INDEX
--- linux-2.6.10-rc3-bk16-orig/Documentation/00-INDEX	2004-12-06 22:24:13.000000000 +0100
+++ linux-2.6.10-rc3-bk16/Documentation/00-INDEX	2004-12-25 22:42:34.000000000 +0100
@@ -254,6 +254,8 @@
 	- directory with info on sound card support.
 sparc/
 	- directory with info on using Linux on Sparc architecture.
+sparse.txt
+	- documentation on installing and using the 'sparse' source checker.
 specialix.txt
 	- info on hardware/driver for specialix IO8+ multiport serial card.
 spinlocks.txt

Re: docs: add sparse howto

[Randy.Dunlap]

Pavel Machek wrote:
> Hi!
> 
> Installing / using sparse is not exactly trivial, this should make
> setting it up easier. Please apply, 
> 								Pavel
> 
> Adapted From: Linus Torvalds <torvalds@osdl.org>
> Signed-off-by: Pavel Machek <pavel@suse.cz>

Hm, good luck, I've sent this one in several times (all dropped :(

http://www.xenotime.net/linux/doc/sparse_howto.txt

-- 
~Randy