/*
   * BCM47XX MTD partitioning
   *
   * Copyright © 2012 Rafał Miłecki <zajec5@gmail.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   */
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/slab.h>
  #include <linux/mtd/mtd.h>
  #include <linux/mtd/partitions.h>
  #include <bcm47xx_nvram.h>
  
  /* 10 parts were found on sflash on Netgear WNDR4500 */
  #define BCM47XXPART_MAX_PARTS		12
  
  /*
   * Amount of bytes we read when analyzing each block of flash memory.
   * Set it big enough to allow detecting partition and reading important data.
   */
  #define BCM47XXPART_BYTES_TO_READ	0x4e8
  
  /* Magics */
  #define BOARD_DATA_MAGIC		0x5246504D	/* MPFR */
  #define BOARD_DATA_MAGIC2		0xBD0D0BBD
  #define CFE_MAGIC			0x43464531	/* 1EFC */
  #define FACTORY_MAGIC			0x59544346	/* FCTY */
  #define POT_MAGIC1			0x54544f50	/* POTT */
  #define POT_MAGIC2			0x504f		/* OP */
  #define ML_MAGIC1			0x39685a42
  #define ML_MAGIC2			0x26594131
  #define TRX_MAGIC			0x30524448
  #define SQSH_MAGIC			0x71736873	/* shsq */
  
  struct trx_header {
  	uint32_t magic;
  	uint32_t length;
  	uint32_t crc32;
  	uint16_t flags;
  	uint16_t version;
  	uint32_t offset[3];
  } __packed;
  
  static void bcm47xxpart_add_part(struct mtd_partition *part, char *name,
  				 u64 offset, uint32_t mask_flags)
  {
  	part->name = name;
  	part->offset = offset;
  	part->mask_flags = mask_flags;
  }
  
  static int bcm47xxpart_parse(struct mtd_info *master,
  			     struct mtd_partition **pparts,
  			     struct mtd_part_parser_data *data)
  {
  	struct mtd_partition *parts;
  	uint8_t i, curr_part = 0;
  	uint32_t *buf;
  	size_t bytes_read;
  	uint32_t offset;
  	uint32_t blocksize = master->erasesize;
  	struct trx_header *trx;
  	int trx_part = -1;
  	int last_trx_part = -1;
  	int possible_nvram_sizes[] = { 0x8000, 0xF000, 0x10000, };
  
  	if (blocksize <= 0x10000)
  		blocksize = 0x10000;
  
  	/* Alloc */
  	parts = kzalloc(sizeof(struct mtd_partition) * BCM47XXPART_MAX_PARTS,
  			GFP_KERNEL);
  	if (!parts)
  		return -ENOMEM;
  
  	buf = kzalloc(BCM47XXPART_BYTES_TO_READ, GFP_KERNEL);
  	if (!buf) {
  		kfree(parts);
  		return -ENOMEM;
  	}
  
  	/* Parse block by block looking for magics */
  	for (offset = 0; offset <= master->size - blocksize;
  	     offset += blocksize) {
  		/* Nothing more in higher memory */
  		if (offset >= 0x2000000)
  			break;
  
  		if (curr_part > BCM47XXPART_MAX_PARTS) {
  			pr_warn("Reached maximum number of partitions, scanning stopped!
  ");
  			break;
  		}
  
  		/* Read beginning of the block */
  		if (mtd_read(master, offset, BCM47XXPART_BYTES_TO_READ,
  			     &bytes_read, (uint8_t *)buf) < 0) {
  			pr_err("mtd_read error while parsing (offset: 0x%X)!
  ",
  			       offset);
  			continue;
  		}
  
  		/* Magic or small NVRAM at 0x400 */
  		if ((buf[0x4e0 / 4] == CFE_MAGIC && buf[0x4e4 / 4] == CFE_MAGIC) ||
  		    (buf[0x400 / 4] == NVRAM_HEADER)) {
  			bcm47xxpart_add_part(&parts[curr_part++], "boot",
  					     offset, MTD_WRITEABLE);
  			continue;
  		}
  
  		/*
  		 * board_data starts with board_id which differs across boards,
  		 * but we can use 'MPFR' (hopefully) magic at 0x100
  		 */
  		if (buf[0x100 / 4] == BOARD_DATA_MAGIC) {
  			bcm47xxpart_add_part(&parts[curr_part++], "board_data",
  					     offset, MTD_WRITEABLE);
  			continue;
  		}
  
  		/* Found on Huawei E970 */
  		if (buf[0x000 / 4] == FACTORY_MAGIC) {
  			bcm47xxpart_add_part(&parts[curr_part++], "factory",
  					     offset, MTD_WRITEABLE);
  			continue;
  		}
  
  		/* POT(TOP) */
  		if (buf[0x000 / 4] == POT_MAGIC1 &&
  		    (buf[0x004 / 4] & 0xFFFF) == POT_MAGIC2) {
  			bcm47xxpart_add_part(&parts[curr_part++], "POT", offset,
  					     MTD_WRITEABLE);
  			continue;
  		}
  
  		/* ML */
  		if (buf[0x010 / 4] == ML_MAGIC1 &&
  		    buf[0x014 / 4] == ML_MAGIC2) {
  			bcm47xxpart_add_part(&parts[curr_part++], "ML", offset,
  					     MTD_WRITEABLE);
  			continue;
  		}
  
  		/* TRX */
  		if (buf[0x000 / 4] == TRX_MAGIC) {
  			trx = (struct trx_header *)buf;
  
  			trx_part = curr_part;
  			bcm47xxpart_add_part(&parts[curr_part++], "firmware",
  					     offset, 0);
  
  			i = 0;
  			/* We have LZMA loader if offset[2] points to sth */
  			if (trx->offset[2]) {
  				bcm47xxpart_add_part(&parts[curr_part++],
  						     "loader",
  						     offset + trx->offset[i],
  						     0);
  				i++;
  			}
  
  			bcm47xxpart_add_part(&parts[curr_part++], "linux",
  					     offset + trx->offset[i], 0);
  			i++;
  
  			/*
  			 * Pure rootfs size is known and can be calculated as:
  			 * trx->length - trx->offset[i]. We don't fill it as
  			 * we want to have jffs2 (overlay) in the same mtd.
  			 */
  			bcm47xxpart_add_part(&parts[curr_part++], "rootfs",
  					     offset + trx->offset[i], 0);
  			i++;
  
  			last_trx_part = curr_part - 1;
  
  			/*
  			 * We have whole TRX scanned, skip to the next part. Use
  			 * roundown (not roundup), as the loop will increase
  			 * offset in next step.
  			 */
  			offset = rounddown(offset + trx->length, blocksize);
  			continue;
  		}
  
  		/* Squashfs on devices not using TRX */
  		if (buf[0x000 / 4] == SQSH_MAGIC) {
  			bcm47xxpart_add_part(&parts[curr_part++], "rootfs",
  					     offset, 0);
  			continue;
  		}
  
  		/* Read middle of the block */
  		if (mtd_read(master, offset + 0x8000, 0x4,
  			     &bytes_read, (uint8_t *)buf) < 0) {
  			pr_err("mtd_read error while parsing (offset: 0x%X)!
  ",
  			       offset);
  			continue;
  		}
  
  		/* Some devices (ex. WNDR3700v3) don't have a standard 'MPFR' */
  		if (buf[0x000 / 4] == BOARD_DATA_MAGIC2) {
  			bcm47xxpart_add_part(&parts[curr_part++], "board_data",
  					     offset, MTD_WRITEABLE);
  			continue;
  		}
  	}
  
  	/* Look for NVRAM at the end of the last block. */
  	for (i = 0; i < ARRAY_SIZE(possible_nvram_sizes); i++) {
  		if (curr_part > BCM47XXPART_MAX_PARTS) {
  			pr_warn("Reached maximum number of partitions, scanning stopped!
  ");
  			break;
  		}
  
  		offset = master->size - possible_nvram_sizes[i];
  		if (mtd_read(master, offset, 0x4, &bytes_read,
  			     (uint8_t *)buf) < 0) {
  			pr_err("mtd_read error while reading at offset 0x%X!
  ",
  			       offset);
  			continue;
  		}
  
  		/* Standard NVRAM */
  		if (buf[0] == NVRAM_HEADER) {
  			bcm47xxpart_add_part(&parts[curr_part++], "nvram",
  					     master->size - blocksize, 0);
  			break;
  		}
  	}
  
  	kfree(buf);
  
  	/*
  	 * Assume that partitions end at the beginning of the one they are
  	 * followed by.
  	 */
  	for (i = 0; i < curr_part; i++) {
  		u64 next_part_offset = (i < curr_part - 1) ?
  				       parts[i + 1].offset : master->size;
  
  		parts[i].size = next_part_offset - parts[i].offset;
  		if (i == last_trx_part && trx_part >= 0)
  			parts[trx_part].size = next_part_offset -
  					       parts[trx_part].offset;
  	}
  
  	*pparts = parts;
  	return curr_part;
  };
  
  static struct mtd_part_parser bcm47xxpart_mtd_parser = {
  	.owner = THIS_MODULE,
  	.parse_fn = bcm47xxpart_parse,
  	.name = "bcm47xxpart",
  };
  
  static int __init bcm47xxpart_init(void)
  {
  	register_mtd_parser(&bcm47xxpart_mtd_parser);
  	return 0;
  }
  
  static void __exit bcm47xxpart_exit(void)
  {
  	deregister_mtd_parser(&bcm47xxpart_mtd_parser);
  }
  
  module_init(bcm47xxpart_init);
  module_exit(bcm47xxpart_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("MTD partitioning for BCM47XX flash memories");