cxl/core: Replace unions with struct_group()

Use the newly introduced struct_group_typed() macro to clean up the
declaration of struct cxl_regs.

Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Ben Widawsky <ben.widawsky@intel.com>
Cc: linux-cxl@vger.kernel.org
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/lkml/1d9a2e6df2a9a35b2cdd50a9a68cac5991e7e5f0.camel@intel.comReviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

drivers/cxl/cxl.h

@@ -75,52 +75,27 @@ static inline int cxl_hdm_decoder_count(u32 cap_hdr)
 #define CXLDEV_MBOX_BG_CMD_STATUS_OFFSET 0x18
 #define CXLDEV_MBOX_PAYLOAD_OFFSET 0x20
 
-#define CXL_COMPONENT_REGS() \
-	void __iomem *hdm_decoder
-
-#define CXL_DEVICE_REGS() \
-	void __iomem *status; \
-	void __iomem *mbox; \
-	void __iomem *memdev
-
-/* See note for 'struct cxl_regs' for the rationale of this organization */
 /*
- * CXL_COMPONENT_REGS - Common set of CXL Component register block base pointers
+ * Using struct_group() allows for per register-block-type helper routines,
+ * without requiring block-type agnostic code to include the prefix.
+ */
+struct cxl_regs {
+	/*
+	 * Common set of CXL Component register block base pointers
 	 * @hdm_decoder: CXL 2.0 8.2.5.12 CXL HDM Decoder Capability Structure
 	 */
-struct cxl_component_regs {
-	CXL_COMPONENT_REGS();
-};
-
-/* See note for 'struct cxl_regs' for the rationale of this organization */
-/*
- * CXL_DEVICE_REGS - Common set of CXL Device register block base pointers
+	struct_group_tagged(cxl_component_regs, component,
+		void __iomem *hdm_decoder;
+	);
+	/*
+	 * Common set of CXL Device register block base pointers
 	 * @status: CXL 2.0 8.2.8.3 Device Status Registers
 	 * @mbox: CXL 2.0 8.2.8.4 Mailbox Registers
 	 * @memdev: CXL 2.0 8.2.8.5 Memory Device Registers
 	 */
-struct cxl_device_regs {
-	CXL_DEVICE_REGS();
-};
-
-/*
- * Note, the anonymous union organization allows for per
- * register-block-type helper routines, without requiring block-type
- * agnostic code to include the prefix.
- */
-struct cxl_regs {
-	union {
-		struct {
-			CXL_COMPONENT_REGS();
-		};
-		struct cxl_component_regs component;
-	};
-	union {
-		struct {
-			CXL_DEVICE_REGS();
-		};
-		struct cxl_device_regs device_regs;
-	};
+	struct_group_tagged(cxl_device_regs, device_regs,
+		void __iomem *status, *mbox, *memdev;
+	);
 };
 
 struct cxl_reg_map {