[pci] Use linker tables for runtime selectable PCI APIs

Use the linker table mechanism to enumerate the underlying PCI I/O
APIs, to allow PCIAPI_CLOUD to become architecture-independent code.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/x86/core/pcidirect.c

@@ -54,5 +54,4 @@ PROVIDE_PCIAPI_INLINE ( direct, pci_write_config_byte );
 PROVIDE_PCIAPI_INLINE ( direct, pci_write_config_word );
 PROVIDE_PCIAPI_INLINE ( direct, pci_write_config_dword );
 PROVIDE_PCIAPI_INLINE ( direct, pci_ioremap );
-
-struct pci_api pcidirect_api = PCIAPI_RUNTIME ( direct );
+PROVIDE_PCIAPI_RUNTIME ( direct, PCIAPI_PRIORITY_DIRECT );

src/arch/x86/include/bits/pci_io.h

@@ -11,6 +11,5 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
 #include <ipxe/pcibios.h>
 #include <ipxe/pcidirect.h>
-#include <ipxe/pcicloud.h>
 
 #endif /* _BITS_PCI_IO_H */

src/arch/x86/include/ipxe/pcibios.h

@@ -155,6 +155,4 @@ PCIAPI_INLINE ( pcbios, pci_ioremap ) ( struct pci_device *pci __unused,
 	return ioremap ( bus_addr, len );
 }
 
-extern struct pci_api pcibios_api;
-
 #endif /* _IPXE_PCIBIOS_H */

src/arch/x86/include/ipxe/pcidirect.h

@@ -165,6 +165,4 @@ PCIAPI_INLINE ( direct, pci_ioremap ) ( struct pci_device *pci __unused,
 	return ioremap ( bus_addr, len );
 }
 
-extern struct pci_api pcidirect_api;
-
 #endif /* _PCIDIRECT_H */

src/arch/x86/interface/pcbios/pcibios.c

@@ -129,5 +129,4 @@ PROVIDE_PCIAPI_INLINE ( pcbios, pci_write_config_byte );
 PROVIDE_PCIAPI_INLINE ( pcbios, pci_write_config_word );
 PROVIDE_PCIAPI_INLINE ( pcbios, pci_write_config_dword );
 PROVIDE_PCIAPI_INLINE ( pcbios, pci_ioremap );
-
-struct pci_api pcibios_api = PCIAPI_RUNTIME ( pcbios );
+PROVIDE_PCIAPI_RUNTIME ( pcbios, PCIAPI_PRIORITY_PCBIOS );

src/config/cloud/ioapi.h

@@ -4,4 +4,7 @@
 #ifdef PLATFORM_pcbios
 #undef PCIAPI_PCBIOS
 #define PCIAPI_CLOUD
+#define PCIAPI_RUNTIME_ECAM
+#define PCIAPI_RUNTIME_PCBIOS
+#define PCIAPI_RUNTIME_DIRECT
 #endif

src/config/config_pci.c

@@ -22,6 +22,7 @@
 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
 #include <config/settings.h>
+#include <config/ioapi.h>
 
 /** @file
  *
@@ -34,3 +35,13 @@ PROVIDE_REQUIRING_SYMBOL();
 #ifdef PCI_SETTINGS
 REQUIRE_OBJECT ( pci_settings );
 #endif
+
+#ifdef PCIAPI_RUNTIME_ECAM
+REQUIRE_OBJECT ( ecam );
+#endif
+#ifdef PCIAPI_RUNTIME_PCBIOS
+REQUIRE_OBJECT ( pcibios );
+#endif
+#ifdef PCIAPI_RUNTIME_DIRECT
+REQUIRE_OBJECT ( pcidirect );
+#endif

src/drivers/bus/ecam.c

@@ -279,5 +279,4 @@ PROVIDE_PCIAPI_INLINE ( ecam, pci_write_config_byte );
 PROVIDE_PCIAPI_INLINE ( ecam, pci_write_config_word );
 PROVIDE_PCIAPI_INLINE ( ecam, pci_write_config_dword );
 PROVIDE_PCIAPI_INLINE ( ecam, pci_ioremap );
-
-struct pci_api ecam_api = PCIAPI_RUNTIME ( ecam );
+PROVIDE_PCIAPI_RUNTIME ( ecam, PCIAPI_PRIORITY_ECAM );

src/drivers/bus/pcicloud.c

@@ -26,9 +26,6 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #include <stdint.h>
 #include <string.h>
 #include <ipxe/pci.h>
-#include <ipxe/ecam.h>
-#include <ipxe/pcibios.h>
-#include <ipxe/pcidirect.h>
 #include <ipxe/pcicloud.h>
 
 /** @file
@@ -37,11 +34,6 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  *
  */
 
-/** Underlying PCI configuration space access APIs */
-static struct pci_api *pcicloud_apis[] = {
-	&ecam_api, &pcibios_api, &pcidirect_api
-};
-
 /** Cached PCI configuration space access API */
 static struct {
 	/** PCI bus:dev.fn address range */
@@ -65,17 +57,14 @@ static struct pci_api * pcicloud_find ( uint32_t busdevfn,
 	uint32_t index;
 	uint32_t first;
 	uint32_t last;
-	unsigned int i;
 
 	/* Return empty range on error */
 	range->count = 0;
 
 	/* Try discovery via all known APIs */
-	for ( i = 0 ; i < ( sizeof ( pcicloud_apis ) /
-			    sizeof ( pcicloud_apis[0] ) ) ; i++ ) {
+	for_each_table_entry ( api, PCI_APIS ) {
 
 		/* Discover via this API */
-		api = pcicloud_apis[i];
 		api->pci_discover ( busdevfn, &candidate );
 
 		/* Check for a matching or new closest allocation */
@@ -135,8 +124,7 @@ static struct pci_api * pcicloud_api ( struct pci_device *pci ) {
 
 	/* Fall back to lowest priority API for any unclaimed gaps in ranges */
 	if ( ! api ) {
-		api = pcicloud_apis[ ( sizeof ( pcicloud_apis ) /
-				       sizeof ( pcicloud_apis[0] ) ) - 1 ];
+		api = ( table_end ( PCI_APIS ) - 1 );
 		range->count = ( range->start - pci->busdevfn );
 		range->start = pci->busdevfn;
 		first = range->start;

src/include/ipxe/ecam.h

@@ -54,6 +54,4 @@ struct ecam_mapping {
 	int rc;
 };
 
-extern struct pci_api ecam_api;
-
 #endif /* _IPXE_ECAM_H */

src/include/ipxe/pci_io.h

@@ -11,6 +11,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
 #include <stdint.h>
 #include <ipxe/api.h>
+#include <ipxe/tables.h>
 #include <ipxe/iomap.h>
 #include <config/ioapi.h>
 
@@ -61,6 +62,7 @@ struct pci_range {
 /* Include all architecture-independent I/O API headers */
 #include <ipxe/null_pci.h>
 #include <ipxe/ecam_io.h>
+#include <ipxe/pcicloud.h>
 #include <ipxe/efi/efi_pci_api.h>
 #include <ipxe/linux/linux_pci.h>
 
@@ -171,23 +173,45 @@ struct pci_api {
 	typeof ( pci_ioremap ) ( * pci_ioremap );
 };
 
+/** Runtime selectable PCI API table */
+#define PCI_APIS __table ( struct pci_api, "pci_apis" )
+
+/**
+ * Declare a runtime selectable PCI API
+ *
+ * In the common case of a non-runtime-selectable PCI I/O API, allow
+ * the runtime API code to be garbage-collected at link time to save
+ * space.
+ */
+#ifdef PCIAPI_CLOUD
+#define __pci_api( priority ) __table_entry ( PCI_APIS, priority )
+#else
+#define __pci_api( priority )
+#endif
+
+/* PCI runtime selectable API priorities */
+#define PCIAPI_PRIORITY_ECAM	01	/**< ACPI ECAM */
+#define PCIAPI_PRIORITY_PCBIOS	02	/**< PCI BIOS calls */
+#define PCIAPI_PRIORITY_DIRECT	03	/**< Direct Type 1 accesses */
+
 /** Provide a runtime selectable PCI I/O API */
-#define PCIAPI_RUNTIME( _subsys ) {					\
-	.name = #_subsys,						\
-	.pci_discover = PCIAPI_INLINE ( _subsys, pci_discover ),	\
+#define PROVIDE_PCIAPI_RUNTIME( subsys, priority )			   \
+	struct pci_api pciapi_ ## subsys __pci_api ( priority ) = {	   \
+		.name = #subsys,					   \
+		.pci_discover = PCIAPI_INLINE ( subsys, pci_discover ),	   \
 		.pci_read_config_byte =					   \
-		PCIAPI_INLINE ( _subsys, pci_read_config_byte ),	\
+			PCIAPI_INLINE ( subsys, pci_read_config_byte ),	   \
 		.pci_read_config_word =					   \
-		PCIAPI_INLINE ( _subsys, pci_read_config_word ),	\
+			PCIAPI_INLINE ( subsys, pci_read_config_word ),	   \
 		.pci_read_config_dword =				   \
-		PCIAPI_INLINE ( _subsys, pci_read_config_dword ),	\
+			PCIAPI_INLINE ( subsys, pci_read_config_dword ),   \
 		.pci_write_config_byte =				   \
-		PCIAPI_INLINE ( _subsys, pci_write_config_byte ),	\
+			PCIAPI_INLINE ( subsys, pci_write_config_byte ),   \
 		.pci_write_config_word =				   \
-		PCIAPI_INLINE ( _subsys, pci_write_config_word ),	\
+			PCIAPI_INLINE ( subsys, pci_write_config_word ),   \
 		.pci_write_config_dword =				   \
-		PCIAPI_INLINE ( _subsys, pci_write_config_dword ),	\
-	.pci_ioremap = PCIAPI_INLINE ( _subsys, pci_ioremap ),		\
+			PCIAPI_INLINE ( subsys, pci_write_config_dword ),  \
+		.pci_ioremap = PCIAPI_INLINE ( subsys, pci_ioremap ),	   \
 	}
 
 #endif /* _IPXE_PCI_IO_H */