helpers: Introduce retry macro

Introduce a macro retry(attempts, condition, expr) for retrying a
condition, which is extensively used in coreboot.

Example usage:

 if (!retry(3, read32(REG) == 0, mdelay(1))
         printk(BIOS_ERR, "Error waiting for REG to be 0\n");

BUG=none
TEST=make tests/commonlib/bsd/helpers-test
TEST=emerge-cherry coreboot
BRANCH=none

Change-Id: I421e4dcab949616bd68b3a14231da744b9f74eeb
Signed-off-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55778
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/src/commonlib/bsd/include/commonlib/bsd/helpers.h b/src/commonlib/bsd/include/commonlib/bsd/helpers.h
index 4e6ebeefdd..376ebaef11 100644
--- a/src/commonlib/bsd/include/commonlib/bsd/helpers.h
+++ b/src/commonlib/bsd/include/commonlib/bsd/helpers.h
@@ -88,4 +88,39 @@
 /* Calculate size of structure member. */
 #define member_size(type, member)	(sizeof(((type *)0)->member))
 
+#define _retry_impl(attempts, condition, expr, ...)	\
+({							\
+	__typeof__(condition) _retry_ret =		\
+		(__typeof__(condition))0;		\
+	int _retry_attempts = (attempts);		\
+	do {						\
+		_retry_ret = (condition);		\
+		if (_retry_ret)				\
+			break;				\
+		if (--_retry_attempts > 0) {		\
+			expr;				\
+		} else {				\
+			break;				\
+		}					\
+	} while (1);					\
+	_retry_ret;					\
+})
+
+/*
+ * Helper macro to retry until a condition becomes true or the maximum number
+ * of attempts is reached. Two forms are supported:
+ *
+ * 1. retry(attempts, condition)
+ * 2. retry(attempts, condition, expr)
+ *
+ * @param attempts	Maximum attempts.
+ * @param condition	Condition to retry for.
+ * @param expr		Procedure to run between each evaluation to "condition".
+ *
+ * @return Condition value if it evaluates to true within the maximum attempts;
+ *	   0 otherwise.
+ */
+#define retry(attempts, condition, ...) \
+	_retry_impl(attempts, condition, __VA_ARGS__)
+
 #endif /* COMMONLIB_BSD_HELPERS_H */