Add scripts/coccinelle/err_cast.cocci

Add a Coccinelle file to use the ERR_CAST function

Before the release 2.6.25, one had to use ERR_PTR(PTR_ERR(...))  to
convert the pointer type of an error. Since then, the function
ERR_CAST has been available for that purpose.
Signed-off-by: Nicolas Palix <npalix@diku.dk>
Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/coccinelle/err_cast.cocci

+///
+/// Use ERR_CAST inlined function instead of ERR_PTR(PTR_ERR(...))
+///
+// Confidence: High
+// Copyright: (C) 2009, 2010 Nicolas Palix, DIKU.  GPLv2.
+// Copyright: (C) 2009, 2010 Julia Lawall, DIKU.  GPLv2.
+// Copyright: (C) 2009, 2010 Gilles Muller, INRIA/LiP6.  GPLv2.
+// URL: http://coccinelle.lip6.fr/
+// Options:
+//
+// Keywords: ERR_PTR, PTR_ERR, ERR_CAST
+// Version min: 2.6.25
+//
+
+virtual context
+virtual patch
+virtual org
+virtual report
+
+
+@ depends on context && !patch && !org && !report@
+expression x;
+@@
+
+* ERR_PTR(PTR_ERR(x))
+
+@ depends on !context && patch && !org && !report @
+expression x;
+@@
+
+- ERR_PTR(PTR_ERR(x))
++ ERR_CAST(x)
+
+@r depends on !context && !patch && (org || report)@
+expression x;
+position p;
+@@
+
+ ERR_PTR@p(PTR_ERR(x))
+
+@script:python depends on org@
+p << r.p;
+x << r.x;
+@@
+
+msg="WARNING ERR_CAST can be used with %s" % (x)
+msg_safe=msg.replace("[","@(").replace("]",")")
+coccilib.org.print_todo(p[0], msg_safe)
+
+@script:python depends on report@
+p << r.p;
+x << r.x;
+@@
+
+msg="WARNING: ERR_CAST can be used with %s" % (x)
+coccilib.report.print_report(p[0], msg)