diff --git a/sys/arm64/arm64/gic_v3_its.c b/sys/arm64/arm64/gic_v3_its.c
index 7d1c529469e0e4..c7287f5035e1f9 100644
--- a/sys/arm64/arm64/gic_v3_its.c
+++ b/sys/arm64/arm64/gic_v3_its.c
@@ -878,31 +878,31 @@ static __inline void
 cmd_format_command(struct its_cmd *cmd, uint8_t cmd_type)
 {
 	/* Command field: DW0 [7:0] */
-	cmd->cmd_dword[0] &= ~0xFFUL;
-	cmd->cmd_dword[0] |= cmd_type & 0xFF;
+	cmd->cmd_dword[0] &= ~CMD_COMMAND_MASK;
+	cmd->cmd_dword[0] |= cmd_type;
 }
 
 static __inline void
 cmd_format_devid(struct its_cmd *cmd, uint32_t devid)
 {
 	/* Device ID field: DW0 [63:32] */
-	cmd->cmd_dword[0] &= ~(0xFFFFFFFFUL << 32);
-	cmd->cmd_dword[0] |= ((uint64_t)devid << 32);
+	cmd->cmd_dword[0] &= ~CMD_DEVID_MASK;
+	cmd->cmd_dword[0] |= ((uint64_t)devid << CMD_DEVID_SHIFT);
 }
 
 static __inline void
 cmd_format_size(struct its_cmd *cmd, uint16_t size)
 {
 	/* Size field: DW1 [4:0] */
-	cmd->cmd_dword[1] &= ~0xFFUL;
-	cmd->cmd_dword[1] |= (size & 0xFF);
+	cmd->cmd_dword[1] &= ~CMD_SIZE_MASK;
+	cmd->cmd_dword[1] |= (size & CMD_SIZE_MASK);
 }
 
 static __inline void
 cmd_format_id(struct its_cmd *cmd, uint32_t id)
 {
 	/* ID field: DW1 [31:0] */
-	cmd->cmd_dword[1] &= ~0xFFFFFFFFUL;
+	cmd->cmd_dword[1] &= ~CMD_ID_MASK;
 	cmd->cmd_dword[1] |= id;
 }
 
@@ -910,15 +910,15 @@ static __inline void
 cmd_format_pid(struct its_cmd *cmd, uint32_t pid)
 {
 	/* Physical ID field: DW1 [63:32] */
-	cmd->cmd_dword[1] &= ~(0xFFFFFFFFUL << 32);
-	cmd->cmd_dword[1] |= ((uint64_t)pid << 32);
+	cmd->cmd_dword[1] &= ~CMD_PID_MASK;
+	cmd->cmd_dword[1] |= ((uint64_t)pid << CMD_PID_SHIFT);
 }
 
 static __inline void
 cmd_format_col(struct its_cmd *cmd, uint16_t col_id)
 {
 	/* Collection field: DW2 [16:0] */
-	cmd->cmd_dword[2] &= ~0xFFFFUL;
+	cmd->cmd_dword[2] &= ~CMD_COL_MASK;
 	cmd->cmd_dword[2] |= col_id;
 }
 
@@ -926,24 +926,24 @@ static __inline void
 cmd_format_target(struct its_cmd *cmd, uint64_t target)
 {
 	/* Target Address field: DW2 [47:16] */
-	cmd->cmd_dword[2] &= ~(0xFFFFFFFFUL << 16);
-	cmd->cmd_dword[2] |= (target & (0xFFFFFFFFUL << 16));
+	cmd->cmd_dword[2] &= ~CMD_TARGET_MASK;
+	cmd->cmd_dword[2] |= (target & CMD_TARGET_MASK);
 }
 
 static __inline void
 cmd_format_itt(struct its_cmd *cmd, uint64_t itt)
 {
 	/* ITT Address field: DW2 [47:8] */
-	cmd->cmd_dword[2] &= ~0xFFFFFFFFFF00UL;
-	cmd->cmd_dword[2] |= (itt & 0xFFFFFFFFFF00UL);
+	cmd->cmd_dword[2] &= ~CMD_ITT_MASK;
+	cmd->cmd_dword[2] |= (itt & CMD_ITT_MASK);
 }
 
 static __inline void
 cmd_format_valid(struct its_cmd *cmd, uint8_t valid)
 {
 	/* Valid field: DW2 [63] */
-	cmd->cmd_dword[2] &= ~(1UL << 63);
-	cmd->cmd_dword[2] |= ((uint64_t)valid << 63);
+	cmd->cmd_dword[2] &= ~CMD_VALID_MASK;
+	cmd->cmd_dword[2] |= ((uint64_t)valid << CMD_VALID_SHIFT);
 }
 
 static __inline void
diff --git a/sys/arm64/arm64/gic_v3_var.h b/sys/arm64/arm64/gic_v3_var.h
index 2bde37d482ed40..b4c7fbbe49a66c 100644
--- a/sys/arm64/arm64/gic_v3_var.h
+++ b/sys/arm64/arm64/gic_v3_var.h
@@ -131,13 +131,36 @@ struct its_cmd {
 	uint64_t	cmd_dword[4];	/* ITS command double word */
 };
 
-#define	ITS_CMD_SYNC	(0x05)
-#define	ITS_CMD_MAPD	(0x08)
-#define	ITS_CMD_MAPC	(0x09)
-#define	ITS_CMD_MAPVI	(0x0a)
-#define	ITS_CMD_MAPI	(0x0b)
-#define	ITS_CMD_INV	(0x0c)
-#define	ITS_CMD_INVALL	(0x0d)
+/* ITS commands encoding */
+#define	ITS_CMD_SYNC		(0x05)
+#define	ITS_CMD_MAPD		(0x08)
+#define	ITS_CMD_MAPC		(0x09)
+#define	ITS_CMD_MAPVI		(0x0a)
+#define	ITS_CMD_MAPI		(0x0b)
+#define	ITS_CMD_INV		(0x0c)
+#define	ITS_CMD_INVALL		(0x0d)
+/* Command */
+#define	CMD_COMMAND_MASK	(0xFFUL)
+/* PCI device ID */
+#define	CMD_DEVID_SHIFT		(32)
+#define	CMD_DEVID_MASK		(0xFFFFFFFFUL << CMD_DEVID_SHIFT)
+/* Size of IRQ ID bitfield */
+#define	CMD_SIZE_MASK		(0xFFUL)
+/* Virtual LPI ID */
+#define	CMD_ID_MASK		(0xFFFFFFFFUL)
+/* Physical LPI ID */
+#define	CMD_PID_SHIFT		(32)
+#define	CMD_PID_MASK		(0xFFFFFFFFUL << CMD_PID_SHIFT)
+/* Collection */
+#define	CMD_COL_MASK		(0xFFFFUL)
+/* Target (CPU or Re-Distributor) */
+#define	CMD_TARGET_SHIFT	(16)
+#define	CMD_TARGET_MASK		(0xFFFFFFFFUL << CMD_TARGET_SHIFT)
+/* Interrupt Translation Table address */
+#define	CMD_ITT_MASK		(0xFFFFFFFFFF00UL)
+/* Valid command bit */
+#define	CMD_VALID_SHIFT		(63)
+#define	CMD_VALID_MASK		(1UL << CMD_VALID_SHIFT)
 
 /*
  * ITS command descriptor.