linux-kernel - [PATCH 2/2] firewire: core: use macro expression for not-registered state of BUS_MANAGER

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Message-ID: <20250913105737.778038-3-o-takashi@sakamocchi.jp>
Date: Sat, 13 Sep 2025 19:57:37 +0900
From: Takashi Sakamoto <o-takashi@...amocchi.jp>
To: linux1394-devel@...ts.sourceforge.net
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] firewire: core: use macro expression for not-registered state of BUS_MANAGER_ID

The value of BUS_MANAGER_ID register has 0x3f when no node_id is
registered. Current implementation uses hard-coded numeric literal but
in the case the macro expression is preferable since it is easy to
distinguish the state from node ID mask.

This commit applies the idea.

Signed-off-by: Takashi Sakamoto <o-takashi@...amocchi.jp>
---
 drivers/firewire/core-card.c | 12 ++++++++----
 drivers/firewire/core.h      |  3 +++
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/firewire/core-card.c b/drivers/firewire/core-card.c
index bf2e7f55b83e..adb90161c4c6 100644
--- a/drivers/firewire/core-card.c
+++ b/drivers/firewire/core-card.c
@@ -327,7 +327,7 @@ static void bm_work(struct work_struct *work)
 		 * next generation.
 		 */
 		__be32 data[2] = {
-			cpu_to_be32(0x3f),
+			cpu_to_be32(BUS_MANAGER_ID_NOT_REGISTERED),
 			cpu_to_be32(local_id),
 		};
 		struct fw_device *irm_device = fw_node_get_device(card->irm_node);
@@ -372,10 +372,14 @@ static void bm_work(struct work_struct *work)
 		if (rcode == RCODE_COMPLETE) {
 			int bm_id = be32_to_cpu(data[0]);
 
-			if (generation == card->generation)
-				card->bm_node_id = bm_id == 0x3f ? local_id : 0xffc0 | bm_id;
+			if (generation == card->generation) {
+				if (bm_id != BUS_MANAGER_ID_NOT_REGISTERED)
+					card->bm_node_id = 0xffc0 & bm_id;
+				else
+					card->bm_node_id = local_id;
+			}
 
-			if (bm_id != 0x3f) {
+			if (bm_id != BUS_MANAGER_ID_NOT_REGISTERED) {
 				spin_unlock_irq(&card->lock);
 
 				// Somebody else is BM.  Only act as IRM.
diff --git a/drivers/firewire/core.h b/drivers/firewire/core.h
index 79eb57fd5812..9e68ebf0673d 100644
--- a/drivers/firewire/core.h
+++ b/drivers/firewire/core.h
@@ -170,6 +170,9 @@ static inline void fw_iso_context_init_work(struct fw_iso_context *ctx, work_fun
 
 /* -topology */
 
+// The initial value of BUS_MANAGER_ID register, to express nothing registered.
+#define BUS_MANAGER_ID_NOT_REGISTERED	0x3f
+
 enum {
 	FW_NODE_CREATED,
 	FW_NODE_UPDATED,
-- 
2.48.1