/*
   * Linux driver for SSFDC Flash Translation Layer (Read only)
   * © 2005 Eptar srl
   * Author: Claudio Lanconelli <lanconelli.claudio@eptar.com>
   *
   * Based on NTFL and MTDBLOCK_RO drivers
   *
   * 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/kernel.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/hdreg.h>
  #include <linux/mtd/mtd.h>
  #include <linux/mtd/nand.h>
  #include <linux/mtd/blktrans.h>
  
  struct ssfdcr_record {
  	struct mtd_blktrans_dev mbd;
  	int usecount;
  	unsigned char heads;
  	unsigned char sectors;
  	unsigned short cylinders;
  	int cis_block;			/* block n. containing CIS/IDI */
  	int erase_size;			/* phys_block_size */
  	unsigned short *logic_block_map; /* all zones (max 8192 phys blocks on
  					    the 128MiB) */
  	int map_len;			/* n. phys_blocks on the card */
  };
  
  #define SSFDCR_MAJOR		257
  #define SSFDCR_PARTN_BITS	3
  
  #define SECTOR_SIZE		512
  #define SECTOR_SHIFT		9
  #define OOB_SIZE		16
  
  #define MAX_LOGIC_BLK_PER_ZONE	1000
  #define MAX_PHYS_BLK_PER_ZONE	1024
  
  #define KiB(x)	( (x) * 1024L )
  #define MiB(x)	( KiB(x) * 1024L )
  
  /** CHS Table
  		1MiB	2MiB	4MiB	8MiB	16MiB	32MiB	64MiB	128MiB
  NCylinder	125	125	250	250	500	500	500	500
  NHead		4	4	4	4	4	8	8	16
  NSector		4	8	8	16	16	16	32	32
  SumSector	2,000	4,000	8,000	16,000	32,000	64,000	128,000	256,000
  SectorSize	512	512	512	512	512	512	512	512
  **/
  
  typedef struct {
  	unsigned long size;
  	unsigned short cyl;
  	unsigned char head;
  	unsigned char sec;
  } chs_entry_t;
  
  /* Must be ordered by size */
  static const chs_entry_t chs_table[] = {
  	{ MiB(  1), 125,  4,  4 },
  	{ MiB(  2), 125,  4,  8 },
  	{ MiB(  4), 250,  4,  8 },
  	{ MiB(  8), 250,  4, 16 },
  	{ MiB( 16), 500,  4, 16 },
  	{ MiB( 32), 500,  8, 16 },
  	{ MiB( 64), 500,  8, 32 },
  	{ MiB(128), 500, 16, 32 },
  	{ 0 },
  };
  
  static int get_chs(unsigned long size, unsigned short *cyl, unsigned char *head,
  			unsigned char *sec)
  {
  	int k;
  	int found = 0;
  
  	k = 0;
  	while (chs_table[k].size > 0 && size > chs_table[k].size)
  		k++;
  
  	if (chs_table[k].size > 0) {
  		if (cyl)
  			*cyl = chs_table[k].cyl;
  		if (head)
  			*head = chs_table[k].head;
  		if (sec)
  			*sec = chs_table[k].sec;
  		found = 1;
  	}
  
  	return found;
  }
  
  /* These bytes are the signature for the CIS/IDI sector */
  static const uint8_t cis_numbers[] = {
  	0x01, 0x03, 0xD9, 0x01, 0xFF, 0x18, 0x02, 0xDF, 0x01, 0x20
  };
  
  /* Read and check for a valid CIS sector */
  static int get_valid_cis_sector(struct mtd_info *mtd)
  {
  	int ret, k, cis_sector;
  	size_t retlen;
  	loff_t offset;
  	uint8_t *sect_buf;
  
  	cis_sector = -1;
  
  	sect_buf = kmalloc(SECTOR_SIZE, GFP_KERNEL);
  	if (!sect_buf)
  		goto out;
  
  	/*
  	 * Look for CIS/IDI sector on the first GOOD block (give up after 4 bad
  	 * blocks). If the first good block doesn't contain CIS number the flash
  	 * is not SSFDC formatted
  	 */
  	for (k = 0, offset = 0; k < 4; k++, offset += mtd->erasesize) {
  		if (mtd_block_isbad(mtd, offset)) {
  			ret = mtd_read(mtd, offset, SECTOR_SIZE, &retlen,
  				       sect_buf);
  
  			/* CIS pattern match on the sector buffer */
  			if (ret < 0 || retlen != SECTOR_SIZE) {
  				printk(KERN_WARNING
  					"SSFDC_RO:can't read CIS/IDI sector
  ");
  			} else if (!memcmp(sect_buf, cis_numbers,
  					sizeof(cis_numbers))) {
  				/* Found */
  				cis_sector = (int)(offset >> SECTOR_SHIFT);
  			} else {
  				pr_debug("SSFDC_RO: CIS/IDI sector not found"
  					" on %s (mtd%d)
  ", mtd->name,
  					mtd->index);
  			}
  			break;
  		}
  	}
  
  	kfree(sect_buf);
   out:
  	return cis_sector;
  }
  
  /* Read physical sector (wrapper to MTD_READ) */
  static int read_physical_sector(struct mtd_info *mtd, uint8_t *sect_buf,
  				int sect_no)
  {
  	int ret;
  	size_t retlen;
  	loff_t offset = (loff_t)sect_no << SECTOR_SHIFT;
  
  	ret = mtd_read(mtd, offset, SECTOR_SIZE, &retlen, sect_buf);
  	if (ret < 0 || retlen != SECTOR_SIZE)
  		return -1;
  
  	return 0;
  }
  
  /* Read redundancy area (wrapper to MTD_READ_OOB */
  static int read_raw_oob(struct mtd_info *mtd, loff_t offs, uint8_t *buf)
  {
  	struct mtd_oob_ops ops;
  	int ret;
  
  	ops.mode = MTD_OPS_RAW;
  	ops.ooboffs = 0;
  	ops.ooblen = OOB_SIZE;
  	ops.oobbuf = buf;
  	ops.datbuf = NULL;
  
  	ret = mtd_read_oob(mtd, offs, &ops);
  	if (ret < 0 || ops.oobretlen != OOB_SIZE)
  		return -1;
  
  	return 0;
  }
  
  /* Parity calculator on a word of n bit size */
  static int get_parity(int number, int size)
  {
   	int k;
  	int parity;
  
  	parity = 1;
  	for (k = 0; k < size; k++) {
  		parity += (number >> k);
  		parity &= 1;
  	}
  	return parity;
  }
  
  /* Read and validate the logical block address field stored in the OOB */
  static int get_logical_address(uint8_t *oob_buf)
  {
  	int block_address, parity;
  	int offset[2] = {6, 11}; /* offset of the 2 address fields within OOB */
  	int j;
  	int ok = 0;
  
  	/*
  	 * Look for the first valid logical address
  	 * Valid address has fixed pattern on most significant bits and
  	 * parity check
  	 */
  	for (j = 0; j < ARRAY_SIZE(offset); j++) {
  		block_address = ((int)oob_buf[offset[j]] << 8) |
  			oob_buf[offset[j]+1];
  
  		/* Check for the signature bits in the address field (MSBits) */
  		if ((block_address & ~0x7FF) == 0x1000) {
  			parity = block_address & 0x01;
  			block_address &= 0x7FF;
  			block_address >>= 1;
  
  			if (get_parity(block_address, 10) != parity) {
  				pr_debug("SSFDC_RO: logical address field%d"
  					"parity error(0x%04X)
  ", j+1,
  					block_address);
  			} else {
  				ok = 1;
  				break;
  			}
  		}
  	}
  
  	if (!ok)
  		block_address = -2;
  
  	pr_debug("SSFDC_RO: get_logical_address() %d
  ",
  		block_address);
  
  	return block_address;
  }
  
  /* Build the logic block map */
  static int build_logical_block_map(struct ssfdcr_record *ssfdc)
  {
  	unsigned long offset;
  	uint8_t oob_buf[OOB_SIZE];
  	int ret, block_address, phys_block;
  	struct mtd_info *mtd = ssfdc->mbd.mtd;
  
  	pr_debug("SSFDC_RO: build_block_map() nblks=%d (%luK)
  ",
  	      ssfdc->map_len,
  	      (unsigned long)ssfdc->map_len * ssfdc->erase_size / 1024);
  
  	/* Scan every physical block, skip CIS block */
  	for (phys_block = ssfdc->cis_block + 1; phys_block < ssfdc->map_len;
  			phys_block++) {
  		offset = (unsigned long)phys_block * ssfdc->erase_size;
  		if (mtd_block_isbad(mtd, offset))
  			continue;	/* skip bad blocks */
  
  		ret = read_raw_oob(mtd, offset, oob_buf);
  		if (ret < 0) {
  			pr_debug("SSFDC_RO: mtd read_oob() failed at %lu
  ",
  				offset);
  			return -1;
  		}
  		block_address = get_logical_address(oob_buf);
  
  		/* Skip invalid addresses */
  		if (block_address >= 0 &&
  				block_address < MAX_LOGIC_BLK_PER_ZONE) {
  			int zone_index;
  
  			zone_index = phys_block / MAX_PHYS_BLK_PER_ZONE;
  			block_address += zone_index * MAX_LOGIC_BLK_PER_ZONE;
  			ssfdc->logic_block_map[block_address] =
  				(unsigned short)phys_block;
  
  			pr_debug("SSFDC_RO: build_block_map() phys_block=%d,"
  				"logic_block_addr=%d, zone=%d
  ",
  				phys_block, block_address, zone_index);
  		}
  	}
  	return 0;
  }
  
  static void ssfdcr_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
  {
  	struct ssfdcr_record *ssfdc;
  	int cis_sector;
  
  	/* Check for small page NAND flash */
  	if (!mtd_type_is_nand(mtd) || mtd->oobsize != OOB_SIZE ||
  	    mtd->size > UINT_MAX)
  		return;
  
  	/* Check for SSDFC format by reading CIS/IDI sector */
  	cis_sector = get_valid_cis_sector(mtd);
  	if (cis_sector == -1)
  		return;
  
  	ssfdc = kzalloc(sizeof(struct ssfdcr_record), GFP_KERNEL);
  	if (!ssfdc)
  		return;
  
  	ssfdc->mbd.mtd = mtd;
  	ssfdc->mbd.devnum = -1;
  	ssfdc->mbd.tr = tr;
  	ssfdc->mbd.readonly = 1;
  
  	ssfdc->cis_block = cis_sector / (mtd->erasesize >> SECTOR_SHIFT);
  	ssfdc->erase_size = mtd->erasesize;
  	ssfdc->map_len = (u32)mtd->size / mtd->erasesize;
  
  	pr_debug("SSFDC_RO: cis_block=%d,erase_size=%d,map_len=%d,n_zones=%d
  ",
  		ssfdc->cis_block, ssfdc->erase_size, ssfdc->map_len,
  		DIV_ROUND_UP(ssfdc->map_len, MAX_PHYS_BLK_PER_ZONE));
  
  	/* Set geometry */
  	ssfdc->heads = 16;
  	ssfdc->sectors = 32;
  	get_chs(mtd->size, NULL, &ssfdc->heads, &ssfdc->sectors);
  	ssfdc->cylinders = (unsigned short)(((u32)mtd->size >> SECTOR_SHIFT) /
  			((long)ssfdc->sectors * (long)ssfdc->heads));
  
  	pr_debug("SSFDC_RO: using C:%d H:%d S:%d == %ld sects
  ",
  		ssfdc->cylinders, ssfdc->heads , ssfdc->sectors,
  		(long)ssfdc->cylinders * (long)ssfdc->heads *
  		(long)ssfdc->sectors);
  
  	ssfdc->mbd.size = (long)ssfdc->heads * (long)ssfdc->cylinders *
  				(long)ssfdc->sectors;
  
  	/* Allocate logical block map */
  	ssfdc->logic_block_map = kmalloc(sizeof(ssfdc->logic_block_map[0]) *
  					 ssfdc->map_len, GFP_KERNEL);
  	if (!ssfdc->logic_block_map)
  		goto out_err;
  	memset(ssfdc->logic_block_map, 0xff, sizeof(ssfdc->logic_block_map[0]) *
  		ssfdc->map_len);
  
  	/* Build logical block map */
  	if (build_logical_block_map(ssfdc) < 0)
  		goto out_err;
  
  	/* Register device + partitions */
  	if (add_mtd_blktrans_dev(&ssfdc->mbd))
  		goto out_err;
  
  	printk(KERN_INFO "SSFDC_RO: Found ssfdc%c on mtd%d (%s)
  ",
  		ssfdc->mbd.devnum + 'a', mtd->index, mtd->name);
  	return;
  
  out_err:
  	kfree(ssfdc->logic_block_map);
          kfree(ssfdc);
  }
  
  static void ssfdcr_remove_dev(struct mtd_blktrans_dev *dev)
  {
  	struct ssfdcr_record *ssfdc = (struct ssfdcr_record *)dev;
  
  	pr_debug("SSFDC_RO: remove_dev (i=%d)
  ", dev->devnum);
  
  	del_mtd_blktrans_dev(dev);
  	kfree(ssfdc->logic_block_map);
  }
  
  static int ssfdcr_readsect(struct mtd_blktrans_dev *dev,
  				unsigned long logic_sect_no, char *buf)
  {
  	struct ssfdcr_record *ssfdc = (struct ssfdcr_record *)dev;
  	int sectors_per_block, offset, block_address;
  
  	sectors_per_block = ssfdc->erase_size >> SECTOR_SHIFT;
  	offset = (int)(logic_sect_no % sectors_per_block);
  	block_address = (int)(logic_sect_no / sectors_per_block);
  
  	pr_debug("SSFDC_RO: ssfdcr_readsect(%lu) sec_per_blk=%d, ofst=%d,"
  		" block_addr=%d
  ", logic_sect_no, sectors_per_block, offset,
  		block_address);
  
  	if (block_address >= ssfdc->map_len)
  		BUG();
  
  	block_address = ssfdc->logic_block_map[block_address];
  
  	pr_debug("SSFDC_RO: ssfdcr_readsect() phys_block_addr=%d
  ",
  		block_address);
  
  	if (block_address < 0xffff) {
  		unsigned long sect_no;
  
  		sect_no = (unsigned long)block_address * sectors_per_block +
  				offset;
  
  		pr_debug("SSFDC_RO: ssfdcr_readsect() phys_sect_no=%lu
  ",
  			sect_no);
  
  		if (read_physical_sector(ssfdc->mbd.mtd, buf, sect_no) < 0)
  			return -EIO;
  	} else {
  		memset(buf, 0xff, SECTOR_SIZE);
  	}
  
  	return 0;
  }
  
  static int ssfdcr_getgeo(struct mtd_blktrans_dev *dev,  struct hd_geometry *geo)
  {
  	struct ssfdcr_record *ssfdc = (struct ssfdcr_record *)dev;
  
  	pr_debug("SSFDC_RO: ssfdcr_getgeo() C=%d, H=%d, S=%d
  ",
  			ssfdc->cylinders, ssfdc->heads, ssfdc->sectors);
  
  	geo->heads = ssfdc->heads;
  	geo->sectors = ssfdc->sectors;
  	geo->cylinders = ssfdc->cylinders;
  
  	return 0;
  }
  
  /****************************************************************************
   *
   * Module stuff
   *
   ****************************************************************************/
  
  static struct mtd_blktrans_ops ssfdcr_tr = {
  	.name		= "ssfdc",
  	.major		= SSFDCR_MAJOR,
  	.part_bits	= SSFDCR_PARTN_BITS,
  	.blksize	= SECTOR_SIZE,
  	.getgeo		= ssfdcr_getgeo,
  	.readsect	= ssfdcr_readsect,
  	.add_mtd	= ssfdcr_add_mtd,
  	.remove_dev	= ssfdcr_remove_dev,
  	.owner		= THIS_MODULE,
  };
  
  static int __init init_ssfdcr(void)
  {
  	printk(KERN_INFO "SSFDC read-only Flash Translation layer
  ");
  
  	return register_mtd_blktrans(&ssfdcr_tr);
  }
  
  static void __exit cleanup_ssfdcr(void)
  {
  	deregister_mtd_blktrans(&ssfdcr_tr);
  }
  
  module_init(init_ssfdcr);
  module_exit(cleanup_ssfdcr);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Claudio Lanconelli <lanconelli.claudio@eptar.com>");
  MODULE_DESCRIPTION("Flash Translation Layer for read-only SSFDC SmartMedia card");