RDMA/siw: Introduce SIW_STAG_MAX_INDEX

Add the macro to remove magic number in the code.
Acked-by: Bernard Metzler <bmt@zurich.ibm.com>
Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Link: https://lore.kernel.org/r/20231113115726.12762-9-guoqing.jiang@linux.devSigned-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/sw/siw/siw_mem.c

@@ -14,18 +14,20 @@
 #include "siw.h"
 #include "siw_mem.h"
 
+/* Stag lookup is based on its index part only (24 bits). */
+#define SIW_STAG_MAX_INDEX	0x00ffffff
+
 /*
- * Stag lookup is based on its index part only (24 bits).
  * The code avoids special Stag of zero and tries to randomize
  * STag values between 1 and SIW_STAG_MAX_INDEX.
  */
 int siw_mem_add(struct siw_device *sdev, struct siw_mem *m)
 {
-	struct xa_limit limit = XA_LIMIT(1, 0x00ffffff);
+	struct xa_limit limit = XA_LIMIT(1, SIW_STAG_MAX_INDEX);
 	u32 id, next;
 
 	get_random_bytes(&next, 4);
-	next &= 0x00ffffff;
+	next &= SIW_STAG_MAX_INDEX;
 
 	if (xa_alloc_cyclic(&sdev->mem_xa, &id, m, limit, &next,
 	    GFP_KERNEL) < 0)
@@ -81,7 +83,7 @@ int siw_mr_add_mem(struct siw_mr *mr, struct ib_pd *pd, void *mem_obj,
 {
 	struct siw_device *sdev = to_siw_dev(pd->device);
 	struct siw_mem *mem = kzalloc(sizeof(*mem), GFP_KERNEL);
-	struct xa_limit limit = XA_LIMIT(1, 0x00ffffff);
+	struct xa_limit limit = XA_LIMIT(1, SIW_STAG_MAX_INDEX);
 	u32 id, next;
 
 	if (!mem)
@@ -97,7 +99,7 @@ int siw_mr_add_mem(struct siw_mr *mr, struct ib_pd *pd, void *mem_obj,
 	kref_init(&mem->ref);
 
 	get_random_bytes(&next, 4);
-	next &= 0x00ffffff;
+	next &= SIW_STAG_MAX_INDEX;
 
 	if (xa_alloc_cyclic(&sdev->mem_xa, &id, mem, limit, &next,
 	    GFP_KERNEL) < 0) {