Commit 6e232cfc authored by David Howells's avatar David Howells Committed by David Woodhouse
Browse files

NOMMU: Add support for direct mapping through mtdconcat if possible 



Add support for direct mapping through mtdconcat, if possible, by attaching the
samebacking_dev_info structure to the master.

It has some restrictions:

 (1) It won't permit direct mapping of concatenated devices that have differing
     BDIs.

 (2) It doesn't support maps that span the 'gap' between devices, although it
     possibly could if the devices spanned across return compatible
     (ie. contiguous) addresses from their get_unmapped_area() ops.

Signed-off-by: default avatarGavin Lambert <gavinl@compacsort.com>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Tested-by: default avatarBernd Schmidt <bernd.schmidt@analog.com>
Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
parent 402d3265

drivers/mtd/mtdconcat.c

+47 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include <linux/slab.h>

#include <linux/sched.h>

#include <linux/types.h>

#include <linux/backing-dev.h>



#include <linux/mtd/mtd.h>

#include <linux/mtd/concat.h>
@@ -683,6 +684,40 @@ static int concat_block_markbad(struct mtd_info *mtd, loff_t ofs) 
	return err;

}



/*

 * try to support NOMMU mmaps on concatenated devices

 * - we don't support subdev spanning as we can't guarantee it'll work

 */

static unsigned long concat_get_unmapped_area(struct mtd_info *mtd,

					      unsigned long len,

					      unsigned long offset,

					      unsigned long flags)

{

	struct mtd_concat *concat = CONCAT(mtd);

	int i;



	for (i = 0; i < concat->num_subdev; i++) {

		struct mtd_info *subdev = concat->subdev[i];



		if (offset >= subdev->size) {

			offset -= subdev->size;

			continue;

		}



		/* we've found the subdev over which the mapping will reside */

		if (offset + len > subdev->size)

			return (unsigned long) -EINVAL;



		if (subdev->get_unmapped_area)

			return subdev->get_unmapped_area(subdev, len, offset,

							 flags);



		break;

	}



	return (unsigned long) -ENOSYS;

}



/*

 * This function constructs a virtual MTD device by concatenating

 * num_devs MTD devices. A pointer to the new device object is
@@ -740,6 +775,8 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[], /* subdevices to c 


	concat->mtd.ecc_stats.badblocks = subdev[0]->ecc_stats.badblocks;



	concat->mtd.backing_dev_info = subdev[0]->backing_dev_info;



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



	for (i = 1; i < num_devs; i++) {
@@ -766,6 +803,15 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[], /* subdevices to c 
				concat->mtd.flags |=

				    subdev[i]->flags & MTD_WRITEABLE;

		}



		/* only permit direct mapping if the BDIs are all the same

		 * - copy-mapping is still permitted

		 */

		if (concat->mtd.backing_dev_info !=

		    subdev[i]->backing_dev_info)

			concat->mtd.backing_dev_info =

				&default_backing_dev_info;



		concat->mtd.size += subdev[i]->size;

		concat->mtd.ecc_stats.badblocks +=

			subdev[i]->ecc_stats.badblocks;
@@ -796,6 +842,7 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[], /* subdevices to c 
	concat->mtd.unlock = concat_unlock;

	concat->mtd.suspend = concat_suspend;

	concat->mtd.resume = concat_resume;

	concat->mtd.get_unmapped_area = concat_get_unmapped_area;



	/*

	 * Combine the erase block size info of the subdevices:

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