genirq/msi: Allow shadow declarations of msi_msg:: $member

Architectures like x86 have their MSI messages in various bits of the data,
address_lo and address_hi field. Composing or decomposing these messages
with bitmasks and shifts is possible, but unreadable gunk.

Allow architectures to provide an architecture specific representation for
each member of msi_msg. Provide empty defaults for each and stick them into
an union.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201024213535.443185-12-dwmw2@infradead.org

include/asm-generic/msi.h

@@ -4,6 +4,8 @@
 
 #include <linux/types.h>
 
+#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
+
 #ifndef NUM_MSI_ALLOC_SCRATCHPAD_REGS
 # define NUM_MSI_ALLOC_SCRATCHPAD_REGS	2
 #endif
@@ -30,4 +32,6 @@ typedef struct msi_alloc_info {
 
 #define GENERIC_MSI_DOMAIN_OPS		1
 
+#endif /* CONFIG_GENERIC_MSI_IRQ_DOMAIN */
+
 #endif

include/linux/msi.h

@@ -4,11 +4,50 @@
 
 #include <linux/kobject.h>
 #include <linux/list.h>
+#include <asm/msi.h>
+
+/* Dummy shadow structures if an architecture does not define them */
+#ifndef arch_msi_msg_addr_lo
+typedef struct arch_msi_msg_addr_lo {
+	u32	address_lo;
+} __attribute__ ((packed)) arch_msi_msg_addr_lo_t;
+#endif
+
+#ifndef arch_msi_msg_addr_hi
+typedef struct arch_msi_msg_addr_hi {
+	u32	address_hi;
+} __attribute__ ((packed)) arch_msi_msg_addr_hi_t;
+#endif
+
+#ifndef arch_msi_msg_data
+typedef struct arch_msi_msg_data {
+	u32	data;
+} __attribute__ ((packed)) arch_msi_msg_data_t;
+#endif
 
+/**
+ * msi_msg - Representation of a MSI message
+ * @address_lo:		Low 32 bits of msi message address
+ * @arch_addrlo:	Architecture specific shadow of @address_lo
+ * @address_hi:		High 32 bits of msi message address
+ *			(only used when device supports it)
+ * @arch_addrhi:	Architecture specific shadow of @address_hi
+ * @data:		MSI message data (usually 16 bits)
+ * @arch_data:		Architecture specific shadow of @data
+ */
 struct msi_msg {
-	u32	address_lo;	/* low 32 bits of msi message address */
-	u32	address_hi;	/* high 32 bits of msi message address */
-	u32	data;		/* 16 bits of msi message data */
+	union {
+		u32			address_lo;
+		arch_msi_msg_addr_lo_t	arch_addr_lo;
+	};
+	union {
+		u32			address_hi;
+		arch_msi_msg_addr_hi_t	arch_addr_hi;
+	};
+	union {
+		u32			data;
+		arch_msi_msg_data_t	arch_data;
+	};
 };
 
 extern int pci_msi_ignore_mask;
@@ -243,7 +282,6 @@ struct msi_controller {
 #ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
 
 #include <linux/irqhandler.h>
-#include <asm/msi.h>
 
 struct irq_domain;
 struct irq_domain_ops;