/*
 * MTD device concatenation layer
 *
 * (C) 2002 Robert Kaiser <rkaiser@sysgo.de>
 *
 * This code is GPL
 *
 * $Id: mtdconcat.c,v 1.3 2002/05/21 21:04:25 dwmw2 Exp $
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/slab.h>

#include <linux/mtd/mtd.h>
#include <linux/mtd/concat.h>

/*
 * Our storage structure:
 * Subdev points to an array of pointers to struct mtd_info objects
 * which is allocated along with this structure
 *
 */
struct mtd_concat {
	struct mtd_info mtd;
	int             num_subdev;
	struct mtd_info **subdev;
};

/*
 * how to calculate the size required for the above structure,
 * including the pointer array subdev points to:
 */
#define SIZEOF_STRUCT_MTD_CONCAT(num_subdev)	\
	((sizeof(struct mtd_concat) + (num_subdev) * sizeof(struct mtd_info *)))


/*
 * Given a pointer to the MTD object in the mtd_concat structure,
 * we can retrieve the pointer to that structure with this macro.
 */
#define CONCAT(x)  ((struct mtd_concat *)(x))

	
/* 
 * MTD methods which look up the relevant subdevice, translate the
 * effective address and pass through to the subdevice.
 */

static int concat_read (struct mtd_info *mtd, loff_t from, size_t len, 
			size_t *retlen, u_char *buf)
{
	struct mtd_concat *concat = CONCAT(mtd);
	int err = -EINVAL;
	int i;

	*retlen = 0;

	for(i = 0; i < concat->num_subdev; i++)
	{
		struct mtd_info *subdev = concat->subdev[i];
		size_t size, retsize;

		if (from >= subdev->size)
		{
			size  = 0;
			from -= subdev->size;
		}
		else
		{
			if (from + len > subdev->size)
				size = subdev->size - from;
			else
				size = len;

			err = subdev->read(subdev, from, size, &retsize, buf);

			if(err)
				break;

			*retlen += retsize;
			len -= size;
			if(len == 0)
				break;

			err = -EINVAL;
			buf += size;
			from = 0;
		}
	}
	return err;
}

static int concat_write (struct mtd_info *mtd, loff_t to, size_t len,
			size_t *retlen, const u_char *buf)
{
	struct mtd_concat *concat = CONCAT(mtd);
	int err = -EINVAL;
	int i;

	if (!(mtd->flags & MTD_WRITEABLE))
		return -EROFS;

	*retlen = 0;

	for(i = 0; i < concat->num_subdev; i++)
	{
		struct mtd_info *subdev = concat->subdev[i];
		size_t size, retsize;

		if (to >= subdev->size)
		{
			size  = 0;
			to -= subdev->size;
		}
		else
		{
			if (to + len > subdev->size)
				size = subdev->size - to;
			else
				size = len;

			if (!(subdev->flags & MTD_WRITEABLE))
				err = -EROFS;
			else
				err = subdev->write(subdev, to, size, &retsize, buf);

			if(err)
				break;

			*retlen += retsize;
			len -= size;
			if(len == 0)
				break;

			err = -EINVAL;
			buf += size;
			to = 0;
		}
	}
	return err;
}

static void concat_erase_callback (struct erase_info *instr)
{
	wake_up((wait_queue_head_t *)instr->priv);
}

static int concat_dev_erase(struct mtd_info *mtd, struct erase_info *erase)
{
	int err;
	wait_queue_head_t waitq;
	DECLARE_WAITQUEUE(wait, current);

	/*
	 * This code was stol^H^H^H^Hinspired by mtdchar.c
	 */
	init_waitqueue_head(&waitq);

	erase->mtd = mtd;
	erase->callback = concat_erase_callback;
	erase->priv = (unsigned long)&waitq;
			
	/*
	 * FIXME: Allow INTERRUPTIBLE. Which means
	 * not having the wait_queue head on the stack.
	 */
	err = mtd->erase(mtd, erase);
	if (!err)
	{
		set_current_state(TASK_UNINTERRUPTIBLE);
		add_wait_queue(&waitq, &wait);
		if (erase->state != MTD_ERASE_DONE && erase->state != MTD_ERASE_FAILED)
			schedule();
		remove_wait_queue(&waitq, &wait);
		set_current_state(TASK_RUNNING);

		err = (erase->state == MTD_ERASE_FAILED) ? -EIO : 0;
	}
	return err;
}

static int concat_erase (struct mtd_info *mtd, struct erase_info *instr)
{
	struct mtd_concat *concat = CONCAT(mtd);
	struct mtd_info *subdev;
	int i, err;
	u_int32_t length;
	struct erase_info *erase;

	if (!(mtd->flags & MTD_WRITEABLE))
		return -EROFS;

	if(instr->addr > concat->mtd.size)
		return -EINVAL;

	if(instr->len + instr->addr > concat->mtd.size)
		return -EINVAL;

	/*
	 * Check for proper erase block alignment of the to-be-erased area.
	 * It is easier to do this based on the super device's erase
	 * region info rather than looking at each particular sub-device
	 * in turn.
	 */
	if (!concat->mtd.numeraseregions)
	{	/* the easy case: device has uniform erase block size */
		if(instr->addr & (concat->mtd.erasesize - 1))
			return -EINVAL;
		if(instr->len & (concat->mtd.erasesize - 1))
			return -EINVAL;
	}
	else
	{	/* device has variable erase size */
		struct mtd_erase_region_info *erase_regions = concat->mtd.eraseregions;

		/*
		 * Find the erase region where the to-be-erased area begins:
		 */
		for(i = 0; i < concat->mtd.numeraseregions && 
		           instr->addr >= erase_regions[i].offset; i++)
			;
		--i;

		/*
		 * Now erase_regions[i] is the region in which the
		 * to-be-erased area begins. Verify that the starting
		 * offset is aligned to this region's erase size:
		 */
		if (instr->addr & (erase_regions[i].erasesize-1))
			return -EINVAL;

		/*
		 * now find the erase region where the to-be-erased area ends:
		 */
		for(; i < concat->mtd.numeraseregions && 
		      (instr->addr + instr->len) >=  erase_regions[i].offset ; ++i)
			;
		--i;
		/*
		 * check if the ending offset is aligned to this region's erase size
		 */
		if ((instr->addr + instr->len) & (erase_regions[i].erasesize-1))
			return -EINVAL;
	}

	/* make a local copy of instr to avoid modifying the caller's struct */
	erase = kmalloc(sizeof(struct erase_info),GFP_KERNEL);

	if (!erase)
		return -ENOMEM;

	*erase = *instr;
	length = instr->len;

	/*
	 * find the subdevice where the to-be-erased area begins, adjust
	 * starting offset to be relative to the subdevice start
	 */
	for(i = 0; i < concat->num_subdev; i++)
	{
		subdev = concat->subdev[i];
		if(subdev->size <= erase->addr)
			erase->addr -= subdev->size;
		else
			break;
    }
	if(i >= concat->num_subdev)	/* must never happen since size */
		BUG();					/* limit has been verified above */

	/* now do the erase: */
	err = 0;
	for(;length > 0; i++)	/* loop for all subevices affected by this request */
	{
		subdev = concat->subdev[i];		/* get current subdevice */

		/* limit length to subdevice's size: */
		if(erase->addr + length > subdev->size)
			erase->len = subdev->size - erase->addr;
		else
			erase->len = length;

		if (!(subdev->flags & MTD_WRITEABLE))
		{
			err = -EROFS;
			break;
		}
		length -= erase->len;
		if ((err = concat_dev_erase(subdev, erase)))
		{
			if(err == -EINVAL)	/* sanity check: must never happen since */
				BUG();			/* block alignment has been checked above */
			break;
		}
		/*
		 * erase->addr specifies the offset of the area to be
		 * erased *within the current subdevice*. It can be
		 * non-zero only the first time through this loop, i.e.
		 * for the first subdevice where blocks need to be erased.
		 * All the following erases must begin at the start of the
		 * current subdevice, i.e. at offset zero.
		 */
		erase->addr = 0;
	}
	kfree(erase);
	if (err)
		return err;

	instr->state = MTD_ERASE_DONE;
	if (instr->callback)
		instr->callback(instr);
	return 0;
}

static int concat_lock (struct mtd_info *mtd, loff_t ofs, size_t len)
{
	struct mtd_concat *concat = CONCAT(mtd);
	int i, err = -EINVAL;

	if ((len + ofs) > mtd->size) 
		return -EINVAL;

	for(i = 0; i < concat->num_subdev; i++)
	{
		struct mtd_info *subdev = concat->subdev[i];
		size_t size;

		if (ofs >= subdev->size)
		{
			size  = 0;
			ofs -= subdev->size;
		}
		else
		{
			if (ofs + len > subdev->size)
				size = subdev->size - ofs;
			else
				size = len;

			err = subdev->lock(subdev, ofs, size);

			if(err)
				break;

			len -= size;
			if(len == 0)
				break;

			err = -EINVAL;
			ofs = 0;
		}
	}
	return err;
}

static int concat_unlock (struct mtd_info *mtd, loff_t ofs, size_t len)
{
	struct mtd_concat *concat = CONCAT(mtd);
	int i, err = 0;

	if ((len + ofs) > mtd->size) 
		return -EINVAL;

	for(i = 0; i < concat->num_subdev; i++)
	{
		struct mtd_info *subdev = concat->subdev[i];
		size_t size;

		if (ofs >= subdev->size)
		{
			size  = 0;
			ofs -= subdev->size;
		}
		else
		{
			if (ofs + len > subdev->size)
				size = subdev->size - ofs;
			else
				size = len;

			err = subdev->unlock(subdev, ofs, size);

			if(err)
				break;

			len -= size;
			if(len == 0)
				break;

			err = -EINVAL;
			ofs = 0;
		}
	}
	return err;
}

static void concat_sync(struct mtd_info *mtd)
{
	struct mtd_concat *concat = CONCAT(mtd);
	int i;

	for(i = 0; i < concat->num_subdev; i++)
	{
		struct mtd_info *subdev = concat->subdev[i];
		subdev->sync(subdev);
	}
}

static int concat_suspend(struct mtd_info *mtd)
{
	struct mtd_concat *concat = CONCAT(mtd);
	int i, rc = 0;

	for(i = 0; i < concat->num_subdev; i++)
	{
		struct mtd_info *subdev = concat->subdev[i];
		if((rc = subdev->suspend(subdev)) < 0)
			return rc;
	}
	return rc;
}

static void concat_resume(struct mtd_info *mtd)
{
	struct mtd_concat *concat = CONCAT(mtd);
	int i;

	for(i = 0; i < concat->num_subdev; i++)
	{
		struct mtd_info *subdev = concat->subdev[i];
		subdev->resume(subdev);
	}
}

/*
 * This function constructs a virtual MTD device by concatenating
 * num_devs MTD devices. A pointer to the new device object is
 * stored to *new_dev upon success. This function does _not_
 * register any devices: this is the caller's responsibility.
 */
struct mtd_info *mtd_concat_create(
	struct mtd_info *subdev[],	/* subdevices to concatenate */
	int num_devs,				/* number of subdevices      */
	char *name)					/* name for the new device   */
{
	int i;
	size_t size;
	struct mtd_concat *concat;
	u_int32_t max_erasesize, curr_erasesize;
	int num_erase_region;

	printk(KERN_NOTICE "Concatenating MTD devices:\n");
	for(i = 0; i < num_devs; i++)
		printk(KERN_NOTICE "(%d): \"%s\"\n", i, subdev[i]->name);
	printk(KERN_NOTICE "into device \"%s\"\n", name);

	/* allocate the device structure */
	size = SIZEOF_STRUCT_MTD_CONCAT(num_devs);
	concat = kmalloc (size, GFP_KERNEL);
	if(!concat)
	{
		printk ("memory allocation error while creating concatenated device \"%s\"\n",
				name);
			return NULL;
	}
	memset(concat, 0, size);
	concat->subdev = (struct mtd_info **)(concat + 1);

	/*
	 * Set up the new "super" device's MTD object structure, check for
	 * incompatibilites between the subdevices.
	 */
	concat->mtd.type      = subdev[0]->type;
	concat->mtd.flags     = subdev[0]->flags;
	concat->mtd.size      = subdev[0]->size;
	concat->mtd.erasesize = subdev[0]->erasesize;
	concat->mtd.oobblock  = subdev[0]->oobblock;
	concat->mtd.oobsize   = subdev[0]->oobsize;
	concat->mtd.ecctype   = subdev[0]->ecctype;
	concat->mtd.eccsize   = subdev[0]->eccsize;

	concat->subdev[0]   = subdev[0];

	for(i = 1; i < num_devs; i++)
	{
		if(concat->mtd.type != subdev[i]->type)
		{
			kfree(concat);
			printk ("Incompatible device type on \"%s\"\n", subdev[i]->name);
			return NULL;
		}
		if(concat->mtd.flags != subdev[i]->flags)
		{	/*
			 * Expect all flags except MTD_WRITEABLE to be equal on
			 * all subdevices.
			 */
			if((concat->mtd.flags ^ subdev[i]->flags) & ~MTD_WRITEABLE)
			{
				kfree(concat);
				printk ("Incompatible device flags on \"%s\"\n", subdev[i]->name);
				return NULL;
			}
			else	/* if writeable attribute differs, make super device writeable */
				concat->mtd.flags |= subdev[i]->flags & MTD_WRITEABLE;
		}
		concat->mtd.size += subdev[i]->size;
		if(concat->mtd.oobblock != subdev[i]->oobblock ||
		   concat->mtd.oobsize  != subdev[i]->oobsize  ||
		   concat->mtd.ecctype  != subdev[i]->ecctype  ||
		   concat->mtd.eccsize  != subdev[i]->eccsize)
		{
			kfree(concat);
			printk ("Incompatible OOB or ECC data on \"%s\"\n", subdev[i]->name);
			return NULL;
		}
		concat->subdev[i] = subdev[i];
		
	}

	concat->num_subdev  = num_devs;
	concat->mtd.name    = name;

	/*
	 * NOTE: for now, we do not provide any readv()/writev() methods
	 *       because they are messy to implement and they are not
	 *       used to a great extent anyway.
	 */
	concat->mtd.erase   = concat_erase;
	concat->mtd.read    = concat_read;
	concat->mtd.write   = concat_write;
	concat->mtd.sync    = concat_sync;
	concat->mtd.lock    = concat_lock;
	concat->mtd.unlock  = concat_unlock;
	concat->mtd.suspend = concat_suspend;
	concat->mtd.resume  = concat_resume;


	/*
	 * Combine the erase block size info of the subdevices:
	 *
	 * first, walk the map of the new device and see how
	 * many changes in erase size we have
	 */
	max_erasesize = curr_erasesize = subdev[0]->erasesize;
	num_erase_region = 1;
	for(i = 0; i < num_devs; i++)
	{
		if(subdev[i]->numeraseregions == 0)
		{	/* current subdevice has uniform erase size */
			if(subdev[i]->erasesize != curr_erasesize)
			{	/* if it differs from the last subdevice's erase size, count it */
				++num_erase_region;
				curr_erasesize = subdev[i]->erasesize;
				if(curr_erasesize > max_erasesize)
					max_erasesize = curr_erasesize;
			}
		}
		else
		{	/* current subdevice has variable erase size */
			int j;
			for(j = 0; j < subdev[i]->numeraseregions; j++)
			{	/* walk the list of erase regions, count any changes */
				if(subdev[i]->eraseregions[j].erasesize != curr_erasesize)
				{
					++num_erase_region;
					curr_erasesize = subdev[i]->eraseregions[j].erasesize;
					if(curr_erasesize > max_erasesize)
						max_erasesize = curr_erasesize;
				}
			}
		}
	}

	if(num_erase_region == 1)
	{	/*
		 * All subdevices have the same uniform erase size.
		 * This is easy:
		 */
		concat->mtd.erasesize = curr_erasesize;
		concat->mtd.numeraseregions = 0;
	}
	else
	{	/*
		 * erase block size varies across the subdevices: allocate
		 * space to store the data describing the variable erase regions
		 */
		struct mtd_erase_region_info *erase_region_p;
		u_int32_t begin, position;

		concat->mtd.erasesize = max_erasesize;
		concat->mtd.numeraseregions = num_erase_region;
		concat->mtd.eraseregions = erase_region_p = kmalloc (
		     num_erase_region * sizeof(struct mtd_erase_region_info), GFP_KERNEL);
		if(!erase_region_p)
		{
			kfree(concat);
			printk ("memory allocation error while creating erase region list"
			        " for device \"%s\"\n", name);
			return NULL;
		}

		/*
		 * walk the map of the new device once more and fill in
		 * in erase region info:
		 */
		curr_erasesize = subdev[0]->erasesize;
		begin = position = 0;
		for(i = 0; i < num_devs; i++)
		{
			if(subdev[i]->numeraseregions == 0)
			{	/* current subdevice has uniform erase size */
				if(subdev[i]->erasesize != curr_erasesize)
				{	/*
					 *  fill in an mtd_erase_region_info structure for the area
					 *  we have walked so far:
					 */
					erase_region_p->offset    = begin;
					erase_region_p->erasesize = curr_erasesize;
					erase_region_p->numblocks = (position - begin) / curr_erasesize;
					begin = position;

					curr_erasesize = subdev[i]->erasesize;
					++erase_region_p;
				}
				position += subdev[i]->size;
			}
			else
			{	/* current subdevice has variable erase size */
				int j;
				for(j = 0; j < subdev[i]->numeraseregions; j++)
				{	/* walk the list of erase regions, count any changes */
					if(subdev[i]->eraseregions[j].erasesize != curr_erasesize)
					{
						erase_region_p->offset    = begin;
						erase_region_p->erasesize = curr_erasesize;
						erase_region_p->numblocks = (position - begin) / curr_erasesize;
						begin = position;

						curr_erasesize = subdev[i]->eraseregions[j].erasesize;
						++erase_region_p;
					}
					position += subdev[i]->eraseregions[j].numblocks * curr_erasesize;
				}
			}
		}
		/* Now write the final entry */
		erase_region_p->offset    = begin;
		erase_region_p->erasesize = curr_erasesize;
		erase_region_p->numblocks = (position - begin) / curr_erasesize;
	}

	return &concat->mtd;
}

/* 
 * This function destroys an MTD object obtained from concat_mtd_devs()
 */

void mtd_concat_destroy(struct mtd_info *mtd)
{
	struct mtd_concat *concat = CONCAT(mtd);
	if(concat->mtd.numeraseregions)
		kfree(concat->mtd.eraseregions);
	kfree(concat);
}


EXPORT_SYMBOL(mtd_concat_create);
EXPORT_SYMBOL(mtd_concat_destroy);


MODULE_LICENSE("GPL");
MODULE_AUTHOR("Robert Kaiser <rkaiser@sysgo.de>");
MODULE_DESCRIPTION("Generic support for concatenating of MTD devices");
