lkml.org 
[lkml]   [2007]   [Feb]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 2/4] NOMMU: Add support for direct mapping through mtdconcat if possible
Date
From: David Howells <dhowells@redhat.com>

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: Gavin Lambert <gavinl@compacsort.com>
Signed-Off-By: David Howells <dhowells@redhat.com>
---

drivers/mtd/mtdconcat.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 47 insertions(+), 0 deletions(-)

diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c
index 880580c..730689b 100644
--- a/drivers/mtd/mtdconcat.c
+++ b/drivers/mtd/mtdconcat.c
@@ -15,6 +15,7 @@
#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>
@@ -686,6 +687,40 @@ static int concat_block_markbad(struct mtd_info *mtd, loff_t ofs)
}

/*
+ * 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
* stored to *new_dev upon success. This function does _not_
@@ -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:
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2007-02-20 20:55    [W:0.569 / U:0.180 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site