[PATCH v5 18/18] dyndbg: change __dynamic_func_call_cls* macros into expressions

[Jim Cromie <jim.cromie@gmail.com>]

The Xe driver's XE_IOCTL_DBG macro calls drm_dbg() from inside an if
(expression).  This breaks when CONFIG_DRM_USE_DYNAMIC_DEBUG=y because
the invoked macro has a do-while-0 wrapper, and is not an expression.

   if (cond && (drm_dbg("expr-form"),1)) {
      ... do some more stuff
   }

Fix for this usage by changing __dynamic_func_call_cls{,_no_desc}
macros into expressions, by replacing the do-while-0s with a ({ })
wrapper.  In the common usage, the trailing ';' converts the
expression into a statement.

   drm_dbg("statement form");

Additionally, change the dynamic_hex_dump() fallback macro (used when
CONFIG_DYNAMIC_DEBUG is disabled) from a do-while-0 statement into a
statement expression returning 0.  This ensures that the fallback form
of dynamic_hex_dump() behaves consistently with its enabled form, and
makes it safe for use in conditional expression contexts.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
---

v5: also convert dynamic_hex_dump() stub

v2:

fix statement-expressions to return 0 (not void) like their respective fallbacks

   1. Add 0; to __dynamic_func_call_cls
   2. Add 0; to __dynamic_func_call_cls_no_desc
   3. Convert the disabled fallback of dynamic_hex_dump from do { ... } while(0) to ({ ... 0; })

move RvB after SoB
---
 include/linux/dynamic_debug.h | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 355f2cb11733..8822f9a3605f 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -238,24 +238,26 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
  * (|_cls):	adds in _DPRINT_CLASS_DFLT as needed
  * (|_no_desc):	former gets callsite descriptor as 1st arg (for prdbgs)
  */
-#define __dynamic_func_call_cls(id, cls, fmt, func, ...) do {	\
+#define __dynamic_func_call_cls(id, cls, fmt, func, ...) ({	\
 	DEFINE_DYNAMIC_DEBUG_METADATA_CLS(id, cls, fmt);	\
 	if (DYNAMIC_DEBUG_BRANCH(id)) {				\
 		func(&id, ##__VA_ARGS__);			\
 		__dynamic_dump_stack(id);			\
 	}							\
-} while (0)
+	0; /* match no_printk return value */			\
+})
 #define __dynamic_func_call(id, fmt, func, ...)				\
 	__dynamic_func_call_cls(id, _DPRINTK_CLASS_DFLT, fmt,		\
 				func, ##__VA_ARGS__)
 
-#define __dynamic_func_call_cls_no_desc(id, cls, fmt, func, ...) do {	\
+#define __dynamic_func_call_cls_no_desc(id, cls, fmt, func, ...) ({	\
 	DEFINE_DYNAMIC_DEBUG_METADATA_CLS(id, cls, fmt);		\
 	if (DYNAMIC_DEBUG_BRANCH(id)) {					\
 		func(__VA_ARGS__);					\
 		__dynamic_dump_stack(id);				\
 	}								\
-} while (0)
+	0; /* match no_printk return value */				\
+})
 #define __dynamic_func_call_no_desc(id, fmt, func, ...)			\
 	__dynamic_func_call_cls_no_desc(id, _DPRINTK_CLASS_DFLT,	\
 					fmt, func, ##__VA_ARGS__)
@@ -335,10 +337,12 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
 	dev_no_printk(KERN_DEBUG, dev, fmt, ##__VA_ARGS__)
 #define dynamic_hex_dump(prefix_str, prefix_type, rowsize,		\
 			 groupsize, buf, len, ascii)			\
-	do { if (0)							\
+({									\
+	if (0)								\
 		print_hex_dump(KERN_DEBUG, prefix_str, prefix_type,	\
-				rowsize, groupsize, buf, len, ascii);	\
-	} while (0)
+			       rowsize, groupsize, buf, len, ascii);	\
+	0;								\
+})
 
 #endif /* CONFIG_DYNAMIC_DEBUG || (CONFIG_DYNAMIC_DEBUG_CORE && DYNAMIC_DEBUG_MODULE) */
 

-- 
2.54.0