diff --git a/drivers/io/io_fip.c b/drivers/io/io_fip.c
index 5a8a294..d291423 100644
--- a/drivers/io/io_fip.c
+++ b/drivers/io/io_fip.c
@@ -134,14 +134,14 @@
 	assert(dev_info != NULL);
 	*dev_info = (io_dev_info_t *)&fip_dev_info; /* cast away const */
 
-	return IO_SUCCESS;
+	return 0;
 }
 
 
 /* Do some basic package checks. */
 static int fip_dev_init(io_dev_info_t *dev_info, const uintptr_t init_params)
 {
-	int result = IO_FAIL;
+	int result;
 	unsigned int image_id = (unsigned int)init_params;
 	uintptr_t backend_handle;
 	fip_toc_header_t header;
@@ -150,28 +150,28 @@
 	/* Obtain a reference to the image by querying the platform layer */
 	result = plat_get_image_source(image_id, &backend_dev_handle,
 				       &backend_image_spec);
-	if (result != IO_SUCCESS) {
+	if (result != 0) {
 		WARN("Failed to obtain reference to image id=%u (%i)\n",
 			image_id, result);
-		result = IO_FAIL;
+		result = -ENOENT;
 		goto fip_dev_init_exit;
 	}
 
 	/* Attempt to access the FIP image */
 	result = io_open(backend_dev_handle, backend_image_spec,
 			 &backend_handle);
-	if (result != IO_SUCCESS) {
+	if (result != 0) {
 		WARN("Failed to access image id=%u (%i)\n", image_id, result);
-		result = IO_FAIL;
+		result = -ENOENT;
 		goto fip_dev_init_exit;
 	}
 
 	result = io_read(backend_handle, (uintptr_t)&header, sizeof(header),
 			&bytes_read);
-	if (result == IO_SUCCESS) {
+	if (result == 0) {
 		if (!is_valid_header(&header)) {
 			WARN("Firmware Image Package header check failed.\n");
-			result = IO_FAIL;
+			result = -ENOENT;
 		} else {
 			VERBOSE("FIP header looks OK.\n");
 		}
@@ -192,7 +192,7 @@
 	backend_dev_handle = (uintptr_t)NULL;
 	backend_image_spec = (uintptr_t)NULL;
 
-	return IO_SUCCESS;
+	return 0;
 }
 
 
@@ -200,7 +200,7 @@
 static int fip_file_open(io_dev_info_t *dev_info, const uintptr_t spec,
 			 io_entity_t *entity)
 {
-	int result = IO_FAIL;
+	int result;
 	uintptr_t backend_handle;
 	const io_uuid_spec_t *uuid_spec = (io_uuid_spec_t *)spec;
 	size_t bytes_read;
@@ -217,23 +217,23 @@
 	 */
 	if (current_file.entry.offset_address != 0) {
 		WARN("fip_file_open : Only one open file at a time.\n");
-		return IO_RESOURCES_EXHAUSTED;
+		return -ENOMEM;
 	}
 
 	/* Attempt to access the FIP image */
 	result = io_open(backend_dev_handle, backend_image_spec,
 			 &backend_handle);
-	if (result != IO_SUCCESS) {
+	if (result != 0) {
 		WARN("Failed to open Firmware Image Package (%i)\n", result);
-		result = IO_FAIL;
+		result = -ENOENT;
 		goto fip_file_open_exit;
 	}
 
 	/* Seek past the FIP header into the Table of Contents */
 	result = io_seek(backend_handle, IO_SEEK_SET, sizeof(fip_toc_header_t));
-	if (result != IO_SUCCESS) {
+	if (result != 0) {
 		WARN("fip_file_open: failed to seek\n");
-		result = IO_FAIL;
+		result = -ENOENT;
 		goto fip_file_open_close;
 	}
 
@@ -243,7 +243,7 @@
 				 (uintptr_t)&current_file.entry,
 				 sizeof(current_file.entry),
 				 &bytes_read);
-		if (result == IO_SUCCESS) {
+		if (result == 0) {
 			if (compare_uuids(&current_file.entry.uuid,
 					  &uuid_spec->uuid) == 0) {
 				found_file = 1;
@@ -265,7 +265,7 @@
 	} else {
 		/* Did not find the file in the FIP. */
 		current_file.entry.offset_address = 0;
-		result = IO_FAIL;
+		result = -ENOENT;
 	}
 
  fip_file_open_close:
@@ -284,7 +284,7 @@
 
 	*length =  ((file_state_t *)entity->info)->entry.size;
 
-	return IO_SUCCESS;
+	return 0;
 }
 
 
@@ -292,7 +292,7 @@
 static int fip_file_read(io_entity_t *entity, uintptr_t buffer, size_t length,
 			  size_t *length_read)
 {
-	int result = IO_FAIL;
+	int result;
 	file_state_t *fp;
 	size_t file_offset;
 	size_t bytes_read;
@@ -306,9 +306,9 @@
 	/* Open the backend, attempt to access the blob image */
 	result = io_open(backend_dev_handle, backend_image_spec,
 			 &backend_handle);
-	if (result != IO_SUCCESS) {
+	if (result != 0) {
 		WARN("Failed to open FIP (%i)\n", result);
-		result = IO_FAIL;
+		result = -ENOENT;
 		goto fip_file_read_exit;
 	}
 
@@ -317,17 +317,17 @@
 	/* Seek to the position in the FIP where the payload lives */
 	file_offset = fp->entry.offset_address + fp->file_pos;
 	result = io_seek(backend_handle, IO_SEEK_SET, file_offset);
-	if (result != IO_SUCCESS) {
+	if (result != 0) {
 		WARN("fip_file_read: failed to seek\n");
-		result = IO_FAIL;
+		result = -ENOENT;
 		goto fip_file_read_close;
 	}
 
 	result = io_read(backend_handle, buffer, length, &bytes_read);
-	if (result != IO_SUCCESS) {
+	if (result != 0) {
 		/* We cannot read our data. Fail. */
 		WARN("Failed to read payload (%i)\n", result);
-		result = IO_FAIL;
+		result = -ENOENT;
 		goto fip_file_read_close;
 	} else {
 		/* Set caller length and new file position. */
@@ -357,7 +357,7 @@
 	/* Clear the Entity info. */
 	entity->info = 0;
 
-	return IO_SUCCESS;
+	return 0;
 }
 
 /* Exported functions */
@@ -365,11 +365,11 @@
 /* Register the Firmware Image Package driver with the IO abstraction */
 int register_io_dev_fip(const io_dev_connector_t **dev_con)
 {
-	int result = IO_FAIL;
+	int result;
 	assert(dev_con != NULL);
 
 	result = io_register_device(&fip_dev_info);
-	if (result == IO_SUCCESS)
+	if (result == 0)
 		*dev_con = &fip_dev_connector;
 
 	return result;
diff --git a/drivers/io/io_memmap.c b/drivers/io/io_memmap.c
index fc06fbb..d45107e 100644
--- a/drivers/io/io_memmap.c
+++ b/drivers/io/io_memmap.c
@@ -101,7 +101,7 @@
 	assert(dev_info != NULL);
 	*dev_info = (io_dev_info_t *)&memmap_dev_info; /* cast away const */
 
-	return IO_SUCCESS;
+	return 0;
 }
 
 
@@ -111,7 +111,7 @@
 {
 	/* NOP */
 	/* TODO: Consider tracking open files and cleaning them up here */
-	return IO_SUCCESS;
+	return 0;
 }
 
 
@@ -120,7 +120,7 @@
 static int memmap_block_open(io_dev_info_t *dev_info, const uintptr_t spec,
 			     io_entity_t *entity)
 {
-	int result = IO_FAIL;
+	int result = -ENOMEM;
 	const io_block_spec_t *block_spec = (io_block_spec_t *)spec;
 
 	/* Since we need to track open state for seek() we only allow one open
@@ -136,10 +136,9 @@
 		/* File cursor offset for seek and incremental reads etc. */
 		current_file.file_pos = 0;
 		entity->info = (uintptr_t)&current_file;
-		result = IO_SUCCESS;
+		result = 0;
 	} else {
 		WARN("A Memmap device is already active. Close first.\n");
-		result = IO_RESOURCES_EXHAUSTED;
 	}
 
 	return result;
@@ -149,7 +148,7 @@
 /* Seek to a particular file offset on the memmap device */
 static int memmap_block_seek(io_entity_t *entity, int mode, ssize_t offset)
 {
-	int result = IO_FAIL;
+	int result = -ENOENT;
 
 	/* We only support IO_SEEK_SET for the moment. */
 	if (mode == IO_SEEK_SET) {
@@ -157,9 +156,7 @@
 
 		/* TODO: can we do some basic limit checks on seek? */
 		((file_state_t *)entity->info)->file_pos = offset;
-		result = IO_SUCCESS;
-	} else {
-		result = IO_FAIL;
+		result = 0;
 	}
 
 	return result;
@@ -184,7 +181,7 @@
 	/* advance the file 'cursor' for incremental reads */
 	fp->file_pos += length;
 
-	return IO_SUCCESS;
+	return 0;
 }
 
 
@@ -207,7 +204,7 @@
 	/* advance the file 'cursor' for incremental writes */
 	fp->file_pos += length;
 
-	return IO_SUCCESS;
+	return 0;
 }
 
 
@@ -221,7 +218,7 @@
 	/* This would be a mem free() if we had malloc.*/
 	memset((void *)&current_file, 0, sizeof(current_file));
 
-	return IO_SUCCESS;
+	return 0;
 }
 
 
@@ -230,11 +227,11 @@
 /* Register the memmap driver with the IO abstraction */
 int register_io_dev_memmap(const io_dev_connector_t **dev_con)
 {
-	int result = IO_FAIL;
+	int result;
 	assert(dev_con != NULL);
 
 	result = io_register_device(&memmap_dev_info);
-	if (result == IO_SUCCESS)
+	if (result == 0)
 		*dev_con = &memmap_dev_connector;
 
 	return result;
diff --git a/drivers/io/io_semihosting.c b/drivers/io/io_semihosting.c
index 8e62be1..63d0f68 100644
--- a/drivers/io/io_semihosting.c
+++ b/drivers/io/io_semihosting.c
@@ -84,10 +84,9 @@
 static int sh_dev_open(const uintptr_t dev_spec __unused,
 		io_dev_info_t **dev_info)
 {
-	int result = IO_SUCCESS;
 	assert(dev_info != NULL);
 	*dev_info = (io_dev_info_t *)&sh_dev_info; /* cast away const */
-	return result;
+	return 0;
 }
 
 
@@ -95,7 +94,7 @@
 static int sh_file_open(io_dev_info_t *dev_info __attribute__((unused)),
 		const uintptr_t spec, io_entity_t *entity)
 {
-	int result = IO_FAIL;
+	int result = -ENOENT;
 	long sh_result = -1;
 	const io_file_spec_t *file_spec = (const io_file_spec_t *)spec;
 
@@ -106,9 +105,7 @@
 
 	if (sh_result > 0) {
 		entity->info = (uintptr_t)sh_result;
-		result = IO_SUCCESS;
-	} else {
-		result = IO_FAIL;
+		result = 0;
 	}
 	return result;
 }
@@ -117,7 +114,6 @@
 /* Seek to a particular file offset on the semi-hosting device */
 static int sh_file_seek(io_entity_t *entity, int mode, ssize_t offset)
 {
-	int result = IO_FAIL;
 	long file_handle, sh_result;
 
 	assert(entity != NULL);
@@ -126,16 +122,14 @@
 
 	sh_result = semihosting_file_seek(file_handle, offset);
 
-	result = (sh_result == 0) ? IO_SUCCESS : IO_FAIL;
-
-	return result;
+	return (sh_result == 0) ? 0 : -ENOENT;
 }
 
 
 /* Return the size of a file on the semi-hosting device */
 static int sh_file_len(io_entity_t *entity, size_t *length)
 {
-	int result = IO_FAIL;
+	int result = -ENOENT;
 
 	assert(entity != NULL);
 	assert(length != NULL);
@@ -144,7 +138,7 @@
 	long sh_result = semihosting_file_length(sh_handle);
 
 	if (sh_result >= 0) {
-		result = IO_SUCCESS;
+		result = 0;
 		*length = (size_t)sh_result;
 	}
 
@@ -156,7 +150,7 @@
 static int sh_file_read(io_entity_t *entity, uintptr_t buffer, size_t length,
 		size_t *length_read)
 {
-	int result = IO_FAIL;
+	int result = -ENOENT;
 	long sh_result = -1;
 	size_t bytes = length;
 	long file_handle;
@@ -171,9 +165,8 @@
 
 	if (sh_result >= 0) {
 		*length_read = (bytes != length) ? bytes : length;
-		result = IO_SUCCESS;
-	} else
-		result = IO_FAIL;
+		result = 0;
+	}
 
 	return result;
 }
@@ -197,14 +190,13 @@
 
 	*length_written = length - bytes;
 
-	return (sh_result == 0) ? IO_SUCCESS : IO_FAIL;
+	return (sh_result == 0) ? 0 : -ENOENT;
 }
 
 
 /* Close a file on the semi-hosting device */
 static int sh_file_close(io_entity_t *entity)
 {
-	int result = IO_FAIL;
 	long sh_result = -1;
 	long file_handle;
 
@@ -214,9 +206,7 @@
 
 	sh_result = semihosting_file_close(file_handle);
 
-	result = (sh_result >= 0) ? IO_SUCCESS : IO_FAIL;
-
-	return result;
+	return (sh_result >= 0) ? 0 : -ENOENT;
 }
 
 
@@ -225,11 +215,11 @@
 /* Register the semi-hosting driver with the IO abstraction */
 int register_io_dev_sh(const io_dev_connector_t **dev_con)
 {
-	int result = IO_FAIL;
+	int result;
 	assert(dev_con != NULL);
 
 	result = io_register_device(&sh_dev_info);
-	if (result == IO_SUCCESS)
+	if (result == 0)
 		*dev_con = &sh_dev_connector;
 
 	return result;
diff --git a/drivers/io/io_storage.c b/drivers/io/io_storage.c
index a3a8186..7cb1a6a 100644
--- a/drivers/io/io_storage.c
+++ b/drivers/io/io_storage.c
@@ -96,7 +96,7 @@
 static int dev_open(const io_dev_connector_t *dev_con, const uintptr_t dev_spec,
 		io_dev_info_t **dev_info)
 {
-	int result = IO_FAIL;
+	int result;
 	assert(dev_info != NULL);
 	assert(is_valid_dev_connector(dev_con));
 
@@ -116,10 +116,10 @@
 /* Locate an entity in the pool, specified by address */
 static int find_first_entity(const io_entity_t *entity, unsigned int *index_out)
 {
-	int result = IO_FAIL;
+	int result = -ENOENT;
 	for (int index = 0; index < MAX_IO_HANDLES; ++index) {
 		if (entity_map[index] == entity) {
-			result = IO_SUCCESS;
+			result = 0;
 			*index_out = index;
 			break;
 		}
@@ -131,17 +131,16 @@
 /* Allocate an entity from the pool and return a pointer to it */
 static int allocate_entity(io_entity_t **entity)
 {
-	int result = IO_FAIL;
+	int result = -ENOMEM;
 	assert(entity != NULL);
 
 	if (entity_count < MAX_IO_HANDLES) {
 		unsigned int index = 0;
 		result = find_first_entity(NULL, &index);
-		assert(result == IO_SUCCESS);
+		assert(result == 0);
 		*entity = entity_map[index] = &entity_pool[index];
 		++entity_count;
-	} else
-		result = IO_RESOURCES_EXHAUSTED;
+	}
 
 	return result;
 }
@@ -150,12 +149,12 @@
 /* Release an entity back to the pool */
 static int free_entity(const io_entity_t *entity)
 {
-	int result = IO_FAIL;
+	int result;
 	unsigned int index = 0;
 	assert(entity != NULL);
 
 	result = find_first_entity(entity, &index);
-	if (result ==  IO_SUCCESS) {
+	if (result ==  0) {
 		entity_map[index] = NULL;
 		--entity_count;
 	}
@@ -169,15 +168,13 @@
 /* Register a device driver */
 int io_register_device(const io_dev_info_t *dev_info)
 {
-	int result = IO_FAIL;
+	int result = -ENOMEM;
 	assert(dev_info != NULL);
 
 	if (dev_count < MAX_IO_DEVICES) {
 		devices[dev_count] = dev_info;
 		dev_count++;
-		result = IO_SUCCESS;
-	} else {
-		result = IO_RESOURCES_EXHAUSTED;
+		result = 0;
 	}
 
 	return result;
@@ -188,7 +185,7 @@
 int io_dev_open(const io_dev_connector_t *dev_con, const uintptr_t dev_spec,
 		uintptr_t *handle)
 {
-	int result = IO_FAIL;
+	int result;
 	assert(handle != NULL);
 
 	result = dev_open(dev_con, dev_spec, (io_dev_info_t **)handle);
@@ -200,18 +197,17 @@
  * re-initialisation */
 int io_dev_init(uintptr_t dev_handle, const uintptr_t init_params)
 {
-	int result = IO_FAIL;
+	int result = 0;
 	assert(dev_handle != (uintptr_t)NULL);
 	assert(is_valid_dev(dev_handle));
 
 	io_dev_info_t *dev = (io_dev_info_t *)dev_handle;
 
+	/* Absence of registered function implies NOP here */
 	if (dev->funcs->dev_init != NULL) {
 		result = dev->funcs->dev_init(dev, init_params);
-	} else {
-		/* Absence of registered function implies NOP here */
-		result = IO_SUCCESS;
 	}
+
 	return result;
 }
 
@@ -221,17 +217,15 @@
 /* Close a connection to a device */
 int io_dev_close(uintptr_t dev_handle)
 {
-	int result = IO_FAIL;
+	int result = 0;
 	assert(dev_handle != (uintptr_t)NULL);
 	assert(is_valid_dev(dev_handle));
 
 	io_dev_info_t *dev = (io_dev_info_t *)dev_handle;
 
+	/* Absence of registered function implies NOP here */
 	if (dev->funcs->dev_close != NULL) {
 		result = dev->funcs->dev_close(dev);
-	} else {
-		/* Absence of registered function implies NOP here */
-		result = IO_SUCCESS;
 	}
 
 	return result;
@@ -244,7 +238,7 @@
 /* Open an IO entity */
 int io_open(uintptr_t dev_handle, const uintptr_t spec, uintptr_t *handle)
 {
-	int result = IO_FAIL;
+	int result;
 	assert((spec != (uintptr_t)NULL) && (handle != NULL));
 	assert(is_valid_dev(dev_handle));
 
@@ -253,11 +247,11 @@
 
 	result = allocate_entity(&entity);
 
-	if (result == IO_SUCCESS) {
+	if (result == 0) {
 		assert(dev->funcs->open != NULL);
 		result = dev->funcs->open(dev, spec, entity);
 
-		if (result == IO_SUCCESS) {
+		if (result == 0) {
 			entity->dev_handle = dev;
 			set_handle(handle, entity);
 		} else
@@ -270,7 +264,7 @@
 /* Seek to a specific position in an IO entity */
 int io_seek(uintptr_t handle, io_seek_mode_t mode, ssize_t offset)
 {
-	int result = IO_FAIL;
+	int result = -ENODEV;
 	assert(is_valid_entity(handle) && is_valid_seek_mode(mode));
 
 	io_entity_t *entity = (io_entity_t *)handle;
@@ -279,8 +273,6 @@
 
 	if (dev->funcs->seek != NULL)
 		result = dev->funcs->seek(entity, mode, offset);
-	else
-		result = IO_NOT_SUPPORTED;
 
 	return result;
 }
@@ -289,7 +281,7 @@
 /* Determine the length of an IO entity */
 int io_size(uintptr_t handle, size_t *length)
 {
-	int result = IO_FAIL;
+	int result = -ENODEV;
 	assert(is_valid_entity(handle) && (length != NULL));
 
 	io_entity_t *entity = (io_entity_t *)handle;
@@ -298,8 +290,6 @@
 
 	if (dev->funcs->size != NULL)
 		result = dev->funcs->size(entity, length);
-	else
-		result = IO_NOT_SUPPORTED;
 
 	return result;
 }
@@ -311,7 +301,7 @@
 		size_t length,
 		size_t *length_read)
 {
-	int result = IO_FAIL;
+	int result = -ENODEV;
 	assert(is_valid_entity(handle) && (buffer != (uintptr_t)NULL));
 
 	io_entity_t *entity = (io_entity_t *)handle;
@@ -320,8 +310,6 @@
 
 	if (dev->funcs->read != NULL)
 		result = dev->funcs->read(entity, buffer, length, length_read);
-	else
-		result = IO_NOT_SUPPORTED;
 
 	return result;
 }
@@ -333,7 +321,7 @@
 		size_t length,
 		size_t *length_written)
 {
-	int result = IO_FAIL;
+	int result = -ENODEV;
 	assert(is_valid_entity(handle) && (buffer != (uintptr_t)NULL));
 
 	io_entity_t *entity = (io_entity_t *)handle;
@@ -343,8 +331,7 @@
 	if (dev->funcs->write != NULL) {
 		result = dev->funcs->write(entity, buffer, length,
 				length_written);
-	} else
-		result = IO_NOT_SUPPORTED;
+	}
 
 	return result;
 }
@@ -353,19 +340,17 @@
 /* Close an IO entity */
 int io_close(uintptr_t handle)
 {
-	int result = IO_FAIL;
+	int result = 0;
 	assert(is_valid_entity(handle));
 
 	io_entity_t *entity = (io_entity_t *)handle;
 
 	io_dev_info_t *dev = entity->dev_handle;
 
+	/* Absence of registered function implies NOP here */
 	if (dev->funcs->close != NULL)
 		result = dev->funcs->close(entity);
-	else {
-		/* Absence of registered function implies NOP here */
-		result = IO_SUCCESS;
-	}
+
 	/* Ignore improbable free_entity failure */
 	(void)free_entity(entity);