[efi] Generalise snpnet_pci_info() to efi_locate_device()

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

src/drivers/net/efi/snpnet.c

 #include <ipxe/efi/Protocol/SimpleNetwork.h>
 #include <ipxe/efi/efi_driver.h>
 #include <ipxe/efi/efi_pci.h>
+#include <ipxe/efi/efi_utils.h>
 #include "snpnet.h"
 
 /** @file
  * @ret rc		Return status code
  */
 static int snpnet_pci_info ( struct efi_device *efidev, struct device *dev ) {
-	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 	EFI_HANDLE device = efidev->device;
-	union {
-		EFI_DEVICE_PATH_PROTOCOL *path;
-		void *interface;
-	} path;
-	EFI_DEVICE_PATH_PROTOCOL *devpath;
-	struct pci_device pci;
 	EFI_HANDLE pci_device;
-	EFI_STATUS efirc;
+	struct pci_device pci;
 	int rc;
 
-	/* Get device path */
-	if ( ( efirc = bs->OpenProtocol ( device,
-					  &efi_device_path_protocol_guid,
-					  &path.interface,
-					  efi_image_handle, device,
-					  EFI_OPEN_PROTOCOL_GET_PROTOCOL ))!=0){
-		rc = -EEFI ( efirc );
-		DBGC ( device, "SNP %p %s cannot open device path: %s\n",
+	/* Find parent PCI device */
+	if ( ( rc = efi_locate_device ( device, &efi_pci_io_protocol_guid,
+					&pci_device ) ) != 0 ) {
+		DBGC ( device, "SNP %p %s is not a PCI device: %s\n",
 		       device, efi_handle_name ( device ), strerror ( rc ) );
-		goto err_open_device_path;
-	}
-	devpath = path.path;
-
-	/* Check for presence of PCI I/O protocol */
-	if ( ( efirc = bs->LocateDevicePath ( &efi_pci_io_protocol_guid,
-					      &devpath, &pci_device ) ) != 0 ) {
-		rc = -EEFI ( efirc );
-		DBGC ( device, "SNP %p %s is not a PCI device\n",
-		       device, efi_handle_name ( device ) );
-		goto err_locate_pci_io;
+		return rc;
 	}
 
 	/* Get PCI device information */
 	if ( ( rc = efipci_info ( pci_device, &pci ) ) != 0 ) {
 		DBGC ( device, "SNP %p %s could not get PCI information: %s\n",
 		       device, efi_handle_name ( device ), strerror ( rc ) );
-		goto err_efipci_info;
+		return rc;
 	}
 
 	/* Populate SNP device information */
 	memcpy ( &dev->desc, &pci.dev.desc, sizeof ( dev->desc ) );
 	snprintf ( dev->name, sizeof ( dev->name ), "SNP-%s", pci.dev.name );
 
- err_efipci_info:
- err_locate_pci_io:
-	bs->CloseProtocol ( device, &efi_device_path_protocol_guid,
-			    efi_image_handle, device );
- err_open_device_path:
-	return rc;
+	return 0;
 }
 
 /**

src/include/ipxe/efi/efi_utils.h

 
 extern EFI_DEVICE_PATH_PROTOCOL *
 efi_devpath_end ( EFI_DEVICE_PATH_PROTOCOL *path );
+extern int efi_locate_device ( EFI_HANDLE device, EFI_GUID *protocol,
+			       EFI_HANDLE *parent );
 extern int efi_child_add ( EFI_HANDLE parent, EFI_HANDLE child );
 extern void efi_child_del ( EFI_HANDLE parent, EFI_HANDLE child );
 

src/interface/efi/efi_utils.c

 	return path;
 }
 
+/**
+ * Locate parent device supporting a given protocol
+ *
+ * @v device		EFI device handle
+ * @v protocol		Protocol GUID
+ * @v parent		Parent EFI device handle to fill in
+ * @ret rc		Return status code
+ */
+int efi_locate_device ( EFI_HANDLE device, EFI_GUID *protocol,
+			EFI_HANDLE *parent ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	union {
+		EFI_DEVICE_PATH_PROTOCOL *path;
+		void *interface;
+	} path;
+	EFI_DEVICE_PATH_PROTOCOL *devpath;
+	EFI_STATUS efirc;
+	int rc;
+
+	/* Get device path */
+	if ( ( efirc = bs->OpenProtocol ( device,
+					  &efi_device_path_protocol_guid,
+					  &path.interface,
+					  efi_image_handle, device,
+					  EFI_OPEN_PROTOCOL_GET_PROTOCOL ))!=0){
+		rc = -EEFI ( efirc );
+		DBGC ( device, "EFIDEV %p %s cannot open device path: %s\n",
+		       device, efi_handle_name ( device ), strerror ( rc ) );
+		goto err_open_device_path;
+	}
+	devpath = path.path;
+
+	/* Check for presence of specified protocol */
+	if ( ( efirc = bs->LocateDevicePath ( protocol, &devpath,
+					      parent ) ) != 0 ) {
+		rc = -EEFI ( efirc );
+		DBGC ( device, "EFIDEV %p %s has no parent supporting %s: %s\n",
+		       device, efi_handle_name ( device ),
+		       efi_guid_ntoa ( protocol ), strerror ( rc ) );
+		goto err_locate_protocol;
+	}
+
+	/* Success */
+	rc = 0;
+
+ err_locate_protocol:
+	bs->CloseProtocol ( device, &efi_device_path_protocol_guid,
+			    efi_image_handle, device );
+ err_open_device_path:
+	return rc;
+}
+
 /**
  * Add EFI device as child of another EFI device
  *