[PATCH v2 14/39] eal: add macro for lowest set CPU bit in a set

FreeBSD supports the CPU_FFS macro as part of the regular cpuset
functions. Add this as RTE_CPU_FFS for all OS's.

From "man CPU_FFS" on FreeBSD 15:

  The CPU_FFS() macro returns the 1-index of the first (lowest) CPU in
  cpuset, or zero if cpuset is empty.  Like with ffs(3), to use the non-
  zero result of CPU_FFS() as a cpu_idx index parameter to any other
  cpuset(9) macro, you must subtract one from the result.

Signed-off-by: Bruce Richardson <[email protected]>
---
 lib/eal/freebsd/include/rte_os.h |  2 ++
 lib/eal/linux/include/rte_os.h   | 10 ++++++++++
 lib/eal/windows/include/rte_os.h |  1 +
 lib/eal/windows/include/sched.h  | 10 ++++++++++
 4 files changed, 23 insertions(+)

diff --git a/lib/eal/freebsd/include/rte_os.h b/lib/eal/freebsd/include/rte_os.h
index 94b9275beb..38fd0e7f05 100644
--- a/lib/eal/freebsd/include/rte_os.h
+++ b/lib/eal/freebsd/include/rte_os.h
@@ -75,4 +75,6 @@ typedef cpuset_t rte_cpuset_t;
 
 #endif /* RTE_EAL_FREEBSD_CPUSET_LEGACY */
 
+#define RTE_CPU_FFS CPU_FFS
+
 #endif /* _RTE_OS_H_ */
diff --git a/lib/eal/linux/include/rte_os.h b/lib/eal/linux/include/rte_os.h
index 20eff0409a..85ce56afaa 100644
--- a/lib/eal/linux/include/rte_os.h
+++ b/lib/eal/linux/include/rte_os.h
@@ -41,6 +41,16 @@ typedef cpu_set_t rte_cpuset_t;
 	RTE_CPU_FILL(&tmp); \
 	CPU_XOR(dst, &tmp, src); \
 } while (0)
+
+static inline int
+rte_cpu_ffs(const rte_cpuset_t *s)
+{
+	for (unsigned int _i = 0; _i < CPU_SETSIZE; _i++)
+		if (CPU_ISSET(_i, s))
+			return (int)(_i + 1);
+	return 0;
+}
+#define RTE_CPU_FFS(s) rte_cpu_ffs(s)
 #endif
 
 #endif /* _RTE_OS_H_ */
diff --git a/lib/eal/windows/include/rte_os.h b/lib/eal/windows/include/rte_os.h
index 2a43cb1f9b..25701c7906 100644
--- a/lib/eal/windows/include/rte_os.h
+++ b/lib/eal/windows/include/rte_os.h
@@ -49,6 +49,7 @@ struct { \
 #define RTE_CPU_OR(dst, src1, src2) CPU_OR(dst, src1, src2)
 #define RTE_CPU_FILL(set) CPU_FILL(set)
 #define RTE_CPU_NOT(dst, src) CPU_NOT(dst, src)
+#define RTE_CPU_FFS(s) CPU_FFS(s)
 
 /* This is an exception without "rte_" prefix, because Windows does have
  * ssize_t, but it's defined in <windows.h> which we avoid to expose.
diff --git a/lib/eal/windows/include/sched.h b/lib/eal/windows/include/sched.h
index 912fed12c2..230de19c76 100644
--- a/lib/eal/windows/include/sched.h
+++ b/lib/eal/windows/include/sched.h
@@ -86,6 +86,16 @@ do { \
 		(dst)->_bits[_i] = (src)->_bits[_i] ^ -1LL; \
 } while (0)
 
+static inline int
+cpu_ffs(const rte_cpuset_t *s)
+{
+	for (unsigned int _i = 0; _i < CPU_SETSIZE; _i++)
+		if (CPU_ISSET(_i, s))
+			return (int)(_i + 1);
+	return 0;
+}
+#define CPU_FFS(s) cpu_ffs(s)
+
 #ifdef __cplusplus
 }
 #endif
-- 
2.53.0