/*
 * Copyright(c) 2015, 2016 Intel Corporation.
 *
 * This file is provided under a dual BSD/GPLv2 license.  When using or
 * redistributing this file, you may do so under either license.
 *
 * GPL LICENSE SUMMARY
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * BSD LICENSE
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *  - Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  - Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *  - Neither the name of Intel Corporation nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include "efivar.h"

/* GUID for HFI1 variables in EFI */
#define HFI1_EFIVAR_GUID EFI_GUID(0xc50a953e, 0xa8b2, 0x42a6, \
		0xbf, 0x89, 0xd3, 0x33, 0xa6, 0xe9, 0xe6, 0xd4)
/* largest EFI data size we expect */
#define EFI_DATA_SIZE 4096

/*
 * Read the named EFI variable.  Return the size of the actual data in *size
 * and a kmalloc'ed buffer in *return_data.  The caller must free the
 * data.  It is guaranteed that *return_data will be NULL and *size = 0
 * if this routine fails.
 *
 * Return 0 on success, -errno on failure.
 */
static int read_efi_var(const char *name, unsigned long *size,
			void **return_data)
{
	efi_status_t status;
	efi_char16_t *uni_name;
	efi_guid_t guid;
	unsigned long temp_size;
	void *temp_buffer;
	void *data;
	int i;
	int ret;

	/* set failure return values */
	*size = 0;
	*return_data = NULL;

	if (!efi_enabled(EFI_RUNTIME_SERVICES))
		return -EOPNOTSUPP;

	uni_name = kcalloc(strlen(name) + 1, sizeof(efi_char16_t), GFP_KERNEL);
	temp_buffer = kzalloc(EFI_DATA_SIZE, GFP_KERNEL);

	if (!uni_name || !temp_buffer) {
		ret = -ENOMEM;
		goto fail;
	}

	/* input: the size of the buffer */
	temp_size = EFI_DATA_SIZE;

	/* convert ASCII to unicode - it is a 1:1 mapping */
	for (i = 0; name[i]; i++)
		uni_name[i] = name[i];

	/* need a variable for our GUID */
	guid = HFI1_EFIVAR_GUID;

	/* call into EFI runtime services */
	status = efi.get_variable(
			uni_name,
			&guid,
			NULL,
			&temp_size,
			temp_buffer);

	/*
	 * It would be nice to call efi_status_to_err() here, but that
	 * is in the EFIVAR_FS code and may not be compiled in.
	 * However, even that is insufficient since it does not cover
	 * EFI_BUFFER_TOO_SMALL which could be an important return.
	 * For now, just split out succces or not found.
	 */
	ret = status == EFI_SUCCESS   ? 0 :
	      status == EFI_NOT_FOUND ? -ENOENT :
					-EINVAL;
	if (ret)
		goto fail;

	/*
	 * We have successfully read the EFI variable into our
	 * temporary buffer.  Now allocate a correctly sized
	 * buffer.
	 */
	data = kmemdup(temp_buffer, temp_size, GFP_KERNEL);
	if (!data) {
		ret = -ENOMEM;
		goto fail;
	}

	*size = temp_size;
	*return_data = data;

fail:
	kfree(uni_name);
	kfree(temp_buffer);

	return ret;
}

/*
 * Read an HFI1 EFI variable of the form:
 *	<PCIe address>-<kind>
 * Return an kalloc'ed array and size of the data.
 *
 * Returns 0 on success, -errno on failure.
 */
int read_hfi1_efi_var(struct hfi1_devdata *dd, const char *kind,
		      unsigned long *size, void **return_data)
{
	char name[64];

	/* create a common prefix */
	snprintf(name, sizeof(name), "%04x:%02x:%02x.%x-%s",
		 pci_domain_nr(dd->pcidev->bus),
		 dd->pcidev->bus->number,
		 PCI_SLOT(dd->pcidev->devfn),
		 PCI_FUNC(dd->pcidev->devfn),
		 kind);

	return read_efi_var(name, size, return_data);
}