/*
 * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <gpxe/dhcp.h>
#include <gpxe/nvs.h>
#include <gpxe/nvo.h>

/** @file
 *
 * Non-volatile stored options
 *
 */

/**
 * Calculate checksum over non-volatile stored options
 *
 * @v nvo		Non-volatile options block
 * @ret sum		Checksum
 */
static unsigned int nvo_checksum ( struct nvo_block *nvo ) {
	uint8_t *data = nvo->data;
	uint8_t sum = 0;
	unsigned int i;

	for ( i = 0 ; i < nvo->total_len ; i++ ) {
		sum += *(data++);
	}
	return sum;
}

/**
 * Load non-volatile stored options from non-volatile storage device
 *
 * @v nvo		Non-volatile options block
 * @ret rc		Return status code
 */
static int nvo_load ( struct nvo_block *nvo ) {
	void *data = nvo->data;
	struct nvo_fragment *frag;
	int rc;

	/* Read data a fragment at a time */
	for ( frag = nvo->fragments ; frag->len ; frag++ ) {
		if ( ( rc = nvs_read ( nvo->nvs, frag->address, data,
				       frag->len ) ) != 0 ) {
			DBGC ( nvo, "NVO %p could not read %zd bytes at "
			       "%#04x\n", nvo, frag->len, frag->address );
			return rc;
		}
		data += frag->len;
	}

	DBGC ( nvo, "NVO %p loaded from non-volatile storage\n", nvo );
	return 0;
}

/**
 * Save non-volatile stored options back to non-volatile storage device
 *
 * @v nvo		Non-volatile options block
 * @ret rc		Return status code
 */
static int nvo_save ( struct nvo_block *nvo ) {
	void *data = nvo->data;
	uint8_t *checksum = data;
	struct nvo_fragment *frag;
	int rc;

	/* Recalculate checksum */
	*checksum -= nvo_checksum ( nvo );

	/* Write data a fragment at a time */
	for ( frag = nvo->fragments ; frag->len ; frag++ ) {
		if ( ( rc = nvs_write ( nvo->nvs, frag->address, data,
					frag->len ) ) != 0 ) {
			DBGC ( nvo, "NVO %p could not write %zd bytes at "
			       "%#04x\n", nvo, frag->len, frag->address );
			return rc;
		}
		data += frag->len;
	}

	DBGC ( nvo, "NVO %p saved to non-volatile storage\n", nvo );
	return 0;
}

/**
 * Parse stored options
 *
 * @v nvo		Non-volatile options block
 *
 * Verifies that the options data is valid, and configures the DHCP
 * options block.  If the data is not valid, it is replaced with an
 * empty options block.
 */
static void nvo_init_dhcpopts ( struct nvo_block *nvo ) {
	uint8_t *options_data;
	size_t options_len;

	/* Steal one byte for the checksum */
	options_data = ( nvo->data + 1 );
	options_len = ( nvo->total_len - 1 );

	/* If checksum fails, or options data starts with a zero,
	 * assume the whole block is invalid.  This should capture the
	 * case of random initial contents.
	 */
	if ( ( nvo_checksum ( nvo ) != 0 ) || ( options_data[0] == 0 ) ) {
		DBGC ( nvo, "NVO %p has checksum %02x and initial byte %02x; "
		       "assuming empty\n", nvo, nvo_checksum ( nvo ),
		       options_data[0] );
		memset ( nvo->data, 0, nvo->total_len );
	}

	dhcpopt_init ( &nvo->dhcpopts, options_data, options_len );
}

/**
 * Store value of NVO setting
 *
 * @v settings		Settings block
 * @v setting		Setting to store
 * @v data		Setting data, or NULL to clear setting
 * @v len		Length of setting data
 * @ret rc		Return status code
 */
static int nvo_store ( struct settings *settings, struct setting *setting,
		       const void *data, size_t len ) {
	struct nvo_block *nvo =
		container_of ( settings, struct nvo_block, settings );
	int rc;

	/* Update stored options */
	if ( ( rc = dhcpopt_store ( &nvo->dhcpopts, setting->tag,
				    data, len ) ) != 0 ) {
		DBGC ( nvo, "NVO %p could not store %zd bytes: %s\n",
		       nvo, len, strerror ( rc ) );
		return rc;
	}

	/* Save updated options to NVS */
	if ( ( rc = nvo_save ( nvo ) ) != 0 )
		return rc;

	return 0;
}

/**
 * Fetch value of NVO setting
 *
 * @v settings		Settings block
 * @v setting		Setting to fetch
 * @v data		Buffer to fill with setting data
 * @v len		Length of buffer
 * @ret len		Length of setting data, or negative error
 *
 * The actual length of the setting will be returned even if
 * the buffer was too small.
 */
static int nvo_fetch ( struct settings *settings, struct setting *setting,
		       void *data, size_t len ) {
	struct nvo_block *nvo =
		container_of ( settings, struct nvo_block, settings );

	return dhcpopt_fetch ( &nvo->dhcpopts, setting->tag, data, len );
}

/** NVO settings operations */
static struct settings_operations nvo_settings_operations = {
	.store = nvo_store,
	.fetch = nvo_fetch,
};

/**
 * Initialise non-volatile stored options
 *
 * @v nvo		Non-volatile options block
 * @v nvs		Underlying non-volatile storage device
 * @v fragments		List of option-containing fragments
 * @v refcnt		Containing object reference counter, or NULL
 */
void nvo_init ( struct nvo_block *nvo, struct nvs_device *nvs,
		struct nvo_fragment *fragments, struct refcnt *refcnt ) {
	nvo->nvs = nvs;
	nvo->fragments = fragments;
	settings_init ( &nvo->settings, &nvo_settings_operations, refcnt,
			"nvo", 0 );
}

/**
 * Register non-volatile stored options
 *
 * @v nvo		Non-volatile options block
 * @v parent		Parent settings block, or NULL
 * @ret rc		Return status code
 */
int register_nvo ( struct nvo_block *nvo, struct settings *parent ) {
	struct nvo_fragment *fragment = nvo->fragments;
	int rc;

	/* Calculate total length of all fragments */
	for ( fragment = nvo->fragments ; fragment->len ; fragment++ )
		nvo->total_len += fragment->len;

	/* Allocate memory for options and read in from NVS */
	nvo->data = malloc ( nvo->total_len );
	if ( ! nvo->data ) {
		DBGC ( nvo, "NVO %p could not allocate %zd bytes\n",
		       nvo, nvo->total_len );
		rc = -ENOMEM;
		goto err_malloc;
	}
	if ( ( rc = nvo_load ( nvo ) ) != 0 )
		goto err_load;

	/* Verify and register options */
	nvo_init_dhcpopts ( nvo );
	if ( ( rc = register_settings ( &nvo->settings, parent ) ) != 0 )
		goto err_register;

	DBGC ( nvo, "NVO %p registered\n", nvo );
	return 0;
	
 err_register:
 err_load:
	free ( nvo->data );
	nvo->data = NULL;
 err_malloc:
	return rc;
}

/**
 * Unregister non-volatile stored options
 *
 * @v nvo		Non-volatile options block
 */
void unregister_nvo ( struct nvo_block *nvo ) {
	unregister_settings ( &nvo->settings );
	free ( nvo->data );
	nvo->data = NULL;
	DBGC ( nvo, "NVO %p unregistered\n", nvo );
}