[PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[kbaidarov]

Description:
The following patch adds readonly block device layer over mtd
that allows to use any filesystem on this device in RO mode and
thus gain faster mount times and better throughput rates.

How it works:
Blocks translation routine was added to read sector function. Assuming
that bad block won't appear during MTD reading and BBT is correct, bad
block is skipped and requested block is lazily mapped to good one.
Block driver based on the mtd readonly device driver mtdblock_ro.c and
translation routine was taken from the patch of Pantelis Antoniou
(which can be found at
http://lists.infradead.org/pipermail/linux-mtd/2004-May/009672.html).

Large major 258 has already been assigned by LANANA.

Signed-off-by: Konstantin Baydarov <kbaidarov@dev.rtsoft.ru>

 drivers/mtd/Kconfig              |    7 +
 drivers/mtd/Makefile             |    1 
 drivers/mtd/mtdblock_ro_bbfree.c |  165 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 173 insertions(+)

Index: mips-kernel-2.6/drivers/mtd/mtdblock_ro_bbfree.c
===================================================================
--- /dev/null
+++ mips-kernel-2.6/drivers/mtd/mtdblock_ro_bbfree.c
@@ -0,0 +1,165 @@
+/*
+ *  Readonly Block Device Layer Over MTD
+ *
+ *  (C) 2006 Baydarov Konstantin <kbaidarov@dev.rtsoft.ru>
+ *           Pantelis Antoniou <panto@intracom.gr>
+ *           David Woodhouse <dwmw2@infradead.org>
+ *
+ *  It allows to use any filesystem on this device in
+ *  RO mode and thus gain faster mount times and better
+ *  throughput rates.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/blktrans.h>
+
+struct mtd_block_map {
+	struct mtd_blktrans_dev dev;
+	/* block map for RO */
+	int32_t *block_map;
+	int32_t block_top;
+	int32_t block_scantop;
+};
+
+static loff_t map_over_bad_blocks(struct mtd_blktrans_dev* dev, loff_t from)
+{
+	int i, block;
+	struct mtd_info *mtd = dev->mtd;
+	struct mtd_block_map* dev_cont = container_of(dev, struct mtd_block_map, dev);
+	int32_t *block_map = dev_cont->block_map;
+	int32_t block_top = dev_cont->block_top;
+	int32_t block_scantop = dev_cont->block_scantop;
+
+	/* if no bad block checking is possible bail out */
+	if (mtd->block_isbad == NULL)
+		return from;
+
+	/* first time in */
+	if (block_map == NULL) {
+		block_top = mtd->size / mtd->erasesize;
+		block_map = kmalloc(sizeof(*block_map) * block_top, GFP_KERNEL);
+		if (block_map == NULL) {
+			printk (KERN_WARNING "map_over_bad_blocks(): unable to allocate block map\n");
+			return -ENOMEM;
+		}
+		for (i = 0; i < block_top; i++)
+			block_map[i] = -1;
+
+		for (i = 0; i < block_top; i++)
+			if ((*mtd->block_isbad)(mtd, i * mtd->erasesize) == 0)
+				break;
+
+		if (i >= block_top) {
+			printk (KERN_WARNING "map_over_bad_blocks(): all blocks bad!\n");
+			return -EIO;
+		}
+		block_scantop = 0;
+		block_map[0] = i;
+
+		DEBUG(0, "mtd: map %d -> %d\n", block_scantop, block_map[block_scantop]);
+	}
+
+	block = ((int)from / mtd->erasesize);
+	if (block >= block_top)
+		return (loff_t)-1;
+
+	/* scan for bad block up to where we want */
+	while (block >= block_scantop) {
+		/* find a non bad block */
+		for (i = block_map[block_scantop] + 1; i < block_top; i++)
+			if ((*mtd->block_isbad)(mtd, i * mtd->erasesize) == 0)
+				break;
+
+		/* exchausted ? */
+		if (i >= block_top) {
+			printk (KERN_WARNING "map_over_bad_blocks(): no more good blocks!\n");
+			return (loff_t)-1;
+		}
+
+		block_map[++block_scantop] = i;
+		DEBUG(0, "mtd: map %d -> %d\n", block_scantop, block_map[block_scantop]);
+	}
+
+	block = block_map[(int)from / mtd->erasesize];
+	from = (block * mtd->erasesize) | ((int)from & (mtd->erasesize - 1));
+	return from;
+}
+
+static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
+			      unsigned long block, char *buf)
+{
+	size_t retlen;
+	unsigned long from;
+
+	from = map_over_bad_blocks(dev, block<<9);
+
+	if (dev->mtd->read(dev->mtd, from, 512, &retlen, buf))
+		return 1;
+	return 0;
+}
+
+static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
+			      unsigned long block, char *buf)
+{
+	size_t retlen;
+
+	if (dev->mtd->write(dev->mtd, (block * 512), 512, &retlen, buf))
+		return 1;
+	return 0;
+}
+
+static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
+{
+	struct mtd_block_map *dev_cont = kmalloc(sizeof(*dev_cont), GFP_KERNEL);
+
+	if (!dev_cont)
+		return;
+
+	memset(dev_cont, 0, sizeof(*dev_cont));
+
+	dev_cont->dev.mtd = mtd;
+	dev_cont->dev.devnum = mtd->index;
+	dev_cont->dev.blksize = 512;
+	dev_cont->dev.size = mtd->size >> 9;
+	dev_cont->dev.tr = tr;
+	dev_cont->dev.readonly = 1;
+
+	add_mtd_blktrans_dev(&(dev_cont->dev));
+}
+
+static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
+{
+	del_mtd_blktrans_dev(dev);
+	kfree(dev);
+}
+
+static struct mtd_blktrans_ops mtdblock_tr = {
+	.name		= "mtdblock",
+	.major		= 258,
+	.part_bits	= 0,
+	.readsect	= mtdblock_readsect,
+	.writesect	= mtdblock_writesect,
+	.add_mtd	= mtdblock_add_mtd,
+	.remove_dev	= mtdblock_remove_dev,
+	.owner		= THIS_MODULE,
+};
+
+static int __init mtdblock_init(void)
+{
+	return register_mtd_blktrans(&mtdblock_tr);
+}
+
+static void __exit mtdblock_exit(void)
+{
+	deregister_mtd_blktrans(&mtdblock_tr);
+}
+
+module_init(mtdblock_init);
+module_exit(mtdblock_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Baydarov Konstantin <kbaidarov@dev.rtsoft.ru>");
+MODULE_DESCRIPTION("Readonly Block Device Layer Over MTD");
Index: mips-kernel-2.6/drivers/mtd/Makefile
===================================================================
--- mips-kernel-2.6.orig/drivers/mtd/Makefile
+++ mips-kernel-2.6/drivers/mtd/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_MTD_AFS_PARTS)	+= afs.o
 obj-$(CONFIG_MTD_CHAR)		+= mtdchar.o
 obj-$(CONFIG_MTD_BLOCK)		+= mtdblock.o mtd_blkdevs.o
 obj-$(CONFIG_MTD_BLOCK_RO)	+= mtdblock_ro.o mtd_blkdevs.o
+obj-$(CONFIG_MTD_BLOCK_RO_BBFREE)	+= mtdblock_ro_bbfree.o mtd_blkdevs.o
 obj-$(CONFIG_FTL)		+= ftl.o mtd_blkdevs.o
 obj-$(CONFIG_NFTL)		+= nftl.o mtd_blkdevs.o
 obj-$(CONFIG_INFTL)		+= inftl.o mtd_blkdevs.o
Index: mips-kernel-2.6/drivers/mtd/Kconfig
===================================================================
--- mips-kernel-2.6.orig/drivers/mtd/Kconfig
+++ mips-kernel-2.6/drivers/mtd/Kconfig
@@ -197,6 +197,13 @@ config MTD_BLOCK_RO
 	  You do not need this option for use with the DiskOnChip devices. For
 	  those, enable NFTL support (CONFIG_NFTL) instead.
 
+config MTD_BLOCK_RO_BBFREE
+	tristate "Readonly bad block free block device access to MTD devices"
+	depends on MTD_BLOCK!=y && MTD && MTD_BLOCK_RO!=y
+	help
+	  Same as readonly block driver, but this allow you to mount read-only file
+	  systems from an MTD device, containing bad blocks.
+
 config FTL
 	tristate "FTL (Flash Translation Layer) support"
 	depends on MTD && BLOCK

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Artem Bityutskiy]

Hello Konstantin,

On Fri, 2006-11-17 at 18:40 +0300, kbaidarov wrote:
> Description:
> The following patch adds readonly block device layer over mtd
> that allows to use any filesystem on this device in RO mode and
> thus gain faster mount times and better throughput rates.

This is very ambition claim. In comparison with what?

> How it works:
> Blocks translation routine was added to read sector function. Assuming
> that bad block won't appear during MTD reading and BBT is correct, bad
> block is skipped and requested block is lazily mapped to good one.
> Block driver based on the mtd readonly device driver mtdblock_ro.c and
> translation routine was taken from the patch of Pantelis Antoniou
> (which can be found at
> http://lists.infradead.org/pipermail/linux-mtd/2004-May/009672.html).
> 

So basically this is bad eraseblock-aware mtdblock_ro? But why you
created a new driver and with so weird name :-) ? Why didn't you just
changed mtdblock_ro? IOW, why you didn't adapt Pantelis' patch instead
and re-send it? (I have no idea why this patch isn't im MTD still,

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Josh Boyer]

On Sat, 2006-11-18 at 15:15 +0200, Artem Bityutskiy wrote:
> Hello Konstantin,
> 
> On Fri, 2006-11-17 at 18:40 +0300, kbaidarov wrote:
> > Description:
> > The following patch adds readonly block device layer over mtd
> > that allows to use any filesystem on this device in RO mode and
> > thus gain faster mount times and better throughput rates.
> 
> This is very ambition claim. In comparison with what?
> 
> > How it works:
> > Blocks translation routine was added to read sector function. Assuming
> > that bad block won't appear during MTD reading and BBT is correct, bad
> > block is skipped and requested block is lazily mapped to good one.
> > Block driver based on the mtd readonly device driver mtdblock_ro.c and
> > translation routine was taken from the patch of Pantelis Antoniou
> > (which can be found at
> > http://lists.infradead.org/pipermail/linux-mtd/2004-May/009672.html).
> > 
> 
> So basically this is bad eraseblock-aware mtdblock_ro? But why you
> created a new driver and with so weird name :-) ? Why didn't you just
> changed mtdblock_ro? IOW, why you didn't adapt Pantelis' patch instead
> and re-send it? (I have no idea why this patch isn't im MTD still,

Because we've consistently told people not to do that.

josh

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Artem Bityutskiy]

On Sat, 2006-11-18 at 07:33 -0600, Josh Boyer wrote:
> Because we've consistently told people not to do that.

OK, but why ?

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Artem Bityutskiy]

On Sat, 2006-11-18 at 15:35 +0200, Artem Bityutskiy wrote:
> On Sat, 2006-11-18 at 07:33 -0600, Josh Boyer wrote:
> > Because we've consistently told people not to do that.
> 
> OK, but why ?
> 

I didn't review this, but I don't see anything bad to do like this

http://lists.infradead.org/pipermail/linux-mtd/2004-May/009683.html

for mtdblock_ro.

What are the objections?


-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Vitaly Wool]

kbaidarov wrote:
> Description:
> The following patch adds readonly block device layer over mtd
> that allows to use any filesystem on this device in RO mode and
> thus gain faster mount times and better throughput rates.
>
> How it works:
> Blocks translation routine was added to read sector function. Assuming
> that bad block won't appear during MTD reading and BBT is correct, bad
> block is skipped and requested block is lazily mapped to good one.
> Block driver based on the mtd readonly device driver mtdblock_ro.c and
> translation routine was taken from the patch of Pantelis Antoniou
> (which can be found at
> http://lists.infradead.org/pipermail/linux-mtd/2004-May/009672.html).
>
> Large major 258 has already been assigned by LANANA.
>
> Signed-off-by: Konstantin Baydarov <kbaidarov@dev.rtsoft.ru>
>   

Acked-by: Vitaly Wool <vwool@ru.mvista.com> ;-)

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Vitaly Wool]

Hi Artem,

Artem Bityutskiy wrote:
> Hello Konstantin,
>
> On Fri, 2006-11-17 at 18:40 +0300, kbaidarov wrote:
>   
>> Description:
>> The following patch adds readonly block device layer over mtd
>> that allows to use any filesystem on this device in RO mode and
>> thus gain faster mount times and better throughput rates.
>>     
>
> This is very ambition claim. In comparison with what?
>   
With JFFS2, for instance. I hope you won't argue than squashfs is faster 
to mount than JFFS2. :-)
Please keep in mind that this is for read-only access.
> So basically this is bad eraseblock-aware mtdblock_ro? But why you
> created a new driver and with so weird name :-) ? Why didn't you just
> changed mtdblock_ro? IOW, why you didn't adapt Pantelis' patch instead
> and re-send it? (I have no idea why this patch isn't im MTD still,
>
>   
Erm, these are several questions in one.
First, this "shim" was arranged as a new driver per dwmw2's request. It 
was our first idea to modify mtdblock_ro, but it didn't work for David.
Next, I pretty much don't understand your phrase about the "weird name", 
though I might be missing something.
And the final thing is this approach is a derivative of Pantelis's 
patch. There were several "points of evolution" within. Please note that 
unlikely to Pantelis's patch, we now don't introduce *any* new fields or 
ifdef's in the generic code, there's no modifications in the existing 
code as well. It became a separate solution 5 screens worth :) It's a 
very low price for being able to use cramfs/squashfs/fat in read-only on 
NAND flash for embedded systems.

Vitaly

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Vitaly Wool]

Artem Bityutskiy wrote:
> On Sat, 2006-11-18 at 07:33 -0600, Josh Boyer wrote:
>   
>> Because we've consistently told people not to do that.
>>     
>
> OK, but why ?
>
>   
B/c it introduces new fields in generic mtd structures which are already 
overcomplicated, and modifies a lot of generic code. I'd expect that 
with this patch applied stuff like mtdcore.c and mtdpart.c becomes 
exposed to possible licensing issues which is definitely not what we aim ;-)

Vitaly

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Artem Bityutskiy]

On Mon, 2006-11-20 at 15:15 +0300, Vitaly Wool wrote:
> B/c it introduces new fields in generic mtd structures which are already 
> overcomplicated, and modifies a lot of generic code. I'd expect that 
> with this patch applied stuff like mtdcore.c and mtdpart.c becomes 
> exposed to possible licensing issues which is definitely not what we aim ;-)

I am talking about something like this:

http://lists.infradead.org/pipermail/linux-mtd/2004-May/009683.html

I do not see it introducing any new field.

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Vitaly Wool]

Artem Bityutskiy wrote:
> I am talking about something like this:
>
> http://lists.infradead.org/pipermail/linux-mtd/2004-May/009683.html
>   
This one unconditionally changes mtdblock, doesn't it?

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Konstantin Baydarov]

Artem Bityutskiy wrote:
> On Mon, 2006-11-20 at 15:15 +0300, Vitaly Wool wrote:
> 
>>B/c it introduces new fields in generic mtd structures which are already 
>>overcomplicated, and modifies a lot of generic code. I'd expect that 
>>with this patch applied stuff like mtdcore.c and mtdpart.c becomes 
>>exposed to possible licensing issues which is definitely not what we aim ;-)
> 
> 
> I am talking about something like this:
> 
> http://lists.infradead.org/pipermail/linux-mtd/2004-May/009683.html
> 
> I do not see it introducing any new field.
> 

I realized it exactly the same way on top of readoly block device. 
Patch, you talking about, definitely needs #ifdef-s and it waste kernel 
RAM statically allocating block_map, block_top, block_scantop 
MAX_MTD_DEVICES times :-).

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Artem Bityutskiy]

On Mon, 2006-11-20 at 16:06 +0300, Vitaly Wool wrote:
> Artem Bityutskiy wrote:
> > I am talking about something like this:
> >
> > http://lists.infradead.org/pipermail/linux-mtd/2004-May/009683.html
> >   
> This one unconditionally changes mtdblock, doesn't it?

Yes.

Basically speaking, mtdblock was designed for NOR flashes and there were
no bad eraseblocks at all. Now you want to utilize it on NANDs. So you
add BB-awareness functionality. And I still think you should changd
mtdblock_ro instead of adding new driver.

Why? Because if you change mtdblock_ro:

1. you do not change semantics at all. in case of old BB-less flashes
all stays the same old way. So I do not understand why you need a new
device number.

2. You make mtdblock_ro workable on NAND. You extend it. You have right
to slightly change the semantics. 1:1 mapping makes no sense in this
case, so it is logical to skip bad blocks. Instead you add a new driver.
Strange.

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Josh Boyer]

On Fri, 2006-11-17 at 18:40 +0300, kbaidarov wrote:
> +	/* scan for bad block up to where we want */
> +	while (block >= block_scantop) {
> +		/* find a non bad block */
> +		for (i = block_map[block_scantop] + 1; i < block_top; i++)
> +			if ((*mtd->block_isbad)(mtd, i * mtd->erasesize) == 0)
> +				break;
> +
> +		/* exchausted ? */

exhausted

> +static struct mtd_blktrans_ops mtdblock_tr = {
> +	.name		= "mtdblock",
> +	.major		= 258,
> +	.part_bits	= 0,
> +	.readsect	= mtdblock_readsect,
> +	.writesect	= mtdblock_writesect,
> +	.add_mtd	= mtdblock_add_mtd,
> +	.remove_dev	= mtdblock_remove_dev,
> +	.owner		= THIS_MODULE,
> +};

You went to the trouble of getting a new major number assigned... why
not call it something other than mtdblock?

> Index: mips-kernel-2.6/drivers/mtd/Makefile
> ===================================================================
> --- mips-kernel-2.6.orig/drivers/mtd/Makefile
> +++ mips-kernel-2.6/drivers/mtd/Makefile
> @@ -17,6 +17,7 @@ obj-$(CONFIG_MTD_AFS_PARTS)	+= afs.o
>  obj-$(CONFIG_MTD_CHAR)		+= mtdchar.o
>  obj-$(CONFIG_MTD_BLOCK)		+= mtdblock.o mtd_blkdevs.o
>  obj-$(CONFIG_MTD_BLOCK_RO)	+= mtdblock_ro.o mtd_blkdevs.o
> +obj-$(CONFIG_MTD_BLOCK_RO_BBFREE)	+= mtdblock_ro_bbfree.o mtd_blkdevs.o
>  obj-$(CONFIG_FTL)		+= ftl.o mtd_blkdevs.o
>  obj-$(CONFIG_NFTL)		+= nftl.o mtd_blkdevs.o
>  obj-$(CONFIG_INFTL)		+= inftl.o mtd_blkdevs.o

All these mtd_blkdevs.o are starting to get ugly.  Why don't we
introduce a CONFIG_MTDBLKDEVS that can be selected by the other Kconfig
options.


> Index: mips-kernel-2.6/drivers/mtd/Kconfig
> ===================================================================
> --- mips-kernel-2.6.orig/drivers/mtd/Kconfig
> +++ mips-kernel-2.6/drivers/mtd/Kconfig
> @@ -197,6 +197,13 @@ config MTD_BLOCK_RO
>  	  You do not need this option for use with the DiskOnChip devices. For
>  	  those, enable NFTL support (CONFIG_NFTL) instead.
> 
> +config MTD_BLOCK_RO_BBFREE
> +	tristate "Readonly bad block free block device access to MTD devices"
> +	depends on MTD_BLOCK!=y && MTD && MTD_BLOCK_RO!=y
> +	help
> +	  Same as readonly block driver, but this allow you to mount read-only file
> +	  systems from an MTD device, containing bad blocks.
> +

This part seems hacky to me...  why can't use use mtdblock or
mtdblock_ro when this is enabled?  And what happens in the module case?

josh

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Vitaly Wool]

Josh Boyer wrote:

<snip>
>> +static struct mtd_blktrans_ops mtdblock_tr = {
>> +	.name		= "mtdblock",
>> +	.major		= 258,
>> +	.part_bits	= 0,
>> +	.readsect	= mtdblock_readsect,
>> +	.writesect	= mtdblock_writesect,
>> +	.add_mtd	= mtdblock_add_mtd,
>> +	.remove_dev	= mtdblock_remove_dev,
>> +	.owner		= THIS_MODULE,
>> +};
>>     
>
> You went to the trouble of getting a new major number assigned... why
> not call it something other than mtdblock?
>   
Agree.
>   
>> Index: mips-kernel-2.6/drivers/mtd/Kconfig
>> ===================================================================
>> --- mips-kernel-2.6.orig/drivers/mtd/Kconfig
>> +++ mips-kernel-2.6/drivers/mtd/Kconfig
>> @@ -197,6 +197,13 @@ config MTD_BLOCK_RO
>>  	  You do not need this option for use with the DiskOnChip devices. For
>>  	  those, enable NFTL support (CONFIG_NFTL) instead.
>>
>> +config MTD_BLOCK_RO_BBFREE
>> +	tristate "Readonly bad block free block device access to MTD devices"
>> +	depends on MTD_BLOCK!=y && MTD && MTD_BLOCK_RO!=y
>> +	help
>> +	  Same as readonly block driver, but this allow you to mount read-only file
>> +	  systems from an MTD device, containing bad blocks.
>> +
>>     
>
> This part seems hacky to me...  why can't use use mtdblock or
> mtdblock_ro when this is enabled?  And what happens in the module case?
>   
I guess this line is borrowed from MTD_BLOCK_RO:

config MTD_BLOCK_RO
        tristate "Readonly block device access to MTD devices"
        depends on MTD_BLOCK!=y && MTD && BLOCK

I think though that these limitations are redundant at least for 
MTD_BLOCK_RO_BBFREE b/c there might be the cases where there're both 
NAND and NOR chips in the system so MTD_BLOCK_RO and MTD_BLOCK_RO_BBFREE 
might be needed to be present in the system at the same time.

Vitaly

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Konstantin Baydarov]

[-- Attachment #1: Type: text/plain, Size: 3379 bytes --]

On Tue, 21 Nov 2006 13:30:15 +0300
Vitaly Wool <vwool@ru.mvista.com> wrote:

> Josh Boyer wrote:
> 
> <snip>
> >> +static struct mtd_blktrans_ops mtdblock_tr = {
> >> +	.name		= "mtdblock",
> >> +	.major		= 258,
> >> +	.part_bits	= 0,
> >> +	.readsect	= mtdblock_readsect,
> >> +	.writesect	= mtdblock_writesect,
> >> +	.add_mtd	= mtdblock_add_mtd,
> >> +	.remove_dev	= mtdblock_remove_dev,
> >> +	.owner		= THIS_MODULE,
> >> +};
> >>     
> >
> > You went to the trouble of getting a new major number assigned...
> > why not call it something other than mtdblock?
> >   
> Agree.
> >   
> >> Index: mips-kernel-2.6/drivers/mtd/Kconfig
> >> ===================================================================
> >> --- mips-kernel-2.6.orig/drivers/mtd/Kconfig
> >> +++ mips-kernel-2.6/drivers/mtd/Kconfig
> >> @@ -197,6 +197,13 @@ config MTD_BLOCK_RO
> >>  	  You do not need this option for use with the DiskOnChip
> >> devices. For those, enable NFTL support (CONFIG_NFTL) instead.
> >>
> >> +config MTD_BLOCK_RO_BBFREE
> >> +	tristate "Readonly bad block free block device access to
> >> MTD devices"
> >> +	depends on MTD_BLOCK!=y && MTD && MTD_BLOCK_RO!=y
> >> +	help
> >> +	  Same as readonly block driver, but this allow you to
> >> mount read-only file
> >> +	  systems from an MTD device, containing bad blocks.
> >> +
> >>     
> >
> > This part seems hacky to me...  why can't use use mtdblock or
> > mtdblock_ro when this is enabled?  And what happens in the module
> > case? 
> I guess this line is borrowed from MTD_BLOCK_RO:
> 
> config MTD_BLOCK_RO
>         tristate "Readonly block device access to MTD devices"
>         depends on MTD_BLOCK!=y && MTD && BLOCK
> 
> I think though that these limitations are redundant at least for 
> MTD_BLOCK_RO_BBFREE b/c there might be the cases where there're both 
> NAND and NOR chips in the system so MTD_BLOCK_RO and
> MTD_BLOCK_RO_BBFREE might be needed to be present in the system at
> the same time.
> 
> Vitaly
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

Corrected typo, renamed driver, got rid from redundant dependency.
Also I've tested mtdblock_ro_bbfree as module - ok.

Interdiff:
diff -u mtd-2.6/drivers/mtd/mtdblock_ro_bbfree.c
mtd-2.6/drivers/mtd/mtdblock_ro_bbfree.c ---
mtd-2.6/drivers/mtd/mtdblock_ro_bbfree.c +++
mtd-2.6/drivers/mtd/mtdblock_ro_bbfree.c @@ -73,7 +73,7 @@
 			if ((*mtd->block_isbad)(mtd, i *
mtd->erasesize) == 0) break;
 
-		/* exchausted ? */
+		/* exhausted ? */
 		if (i >= block_top) {
 			printk (KERN_WARNING "map_over_bad_blocks():
no more good blocks!\n"); return (loff_t)-1;
@@ -137,7 +137,7 @@
 }
 
 static struct mtd_blktrans_ops mtdblock_tr = {
-	.name		= "mtdblock",
+	.name		= "mtdblock_bbfree",
 	.major		= 258,
 	.part_bits	= 0,
 	.readsect	= mtdblock_readsect,
diff -u mtd-2.6/drivers/mtd/Kconfig mtd-2.6/drivers/mtd/Kconfig
--- mtd-2.6/drivers/mtd/Kconfig
+++ mtd-2.6/drivers/mtd/Kconfig
@@ -199,7 +199,7 @@
 
 config MTD_BLOCK_RO_BBFREE
 	tristate "Readonly bad block free block device access to MTD
devices"
-	depends on MTD_BLOCK!=y && MTD && MTD_BLOCK_RO!=y
+	depends on MTD_BLOCK!=y && MTD
 	help
 	  Same as readonly block driver, but this allow you to mount
read-only file systems from an MTD device, containing bad blocks.

Whole patch is attached.

[-- Attachment #2: bbfree_mtd_ro.patch --]
[-- Type: text/x-patch, Size: 5996 bytes --]

 drivers/mtd/Kconfig              |    7 +
 drivers/mtd/Makefile             |    1 
 drivers/mtd/mtdblock_ro_bbfree.c |  165 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 173 insertions(+)

Index: mtd-2.6/drivers/mtd/mtdblock_ro_bbfree.c
===================================================================
--- /dev/null
+++ mtd-2.6/drivers/mtd/mtdblock_ro_bbfree.c
@@ -0,0 +1,165 @@
+/*
+ *  Readonly Block Device Layer Over MTD
+ *
+ *  (C) 2006 Baydarov Konstantin <kbaidarov@dev.rtsoft.ru>
+ *           Pantelis Antoniou <panto@intracom.gr>
+ *           David Woodhouse <dwmw2@infradead.org>
+ *
+ *  It allows to use any filesystem on this device in
+ *  RO mode and thus gain faster mount times and better
+ *  throughput rates.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/blktrans.h>
+
+struct mtd_block_map {
+	struct mtd_blktrans_dev dev;
+	/* block map for RO */
+	int32_t *block_map;
+	int32_t block_top;
+	int32_t block_scantop;
+};
+
+static loff_t map_over_bad_blocks(struct mtd_blktrans_dev* dev, loff_t from)
+{
+	int i, block;
+	struct mtd_info *mtd = dev->mtd;
+	struct mtd_block_map* dev_cont = container_of(dev, struct mtd_block_map, dev);
+	int32_t *block_map = dev_cont->block_map;
+	int32_t block_top = dev_cont->block_top;
+	int32_t block_scantop = dev_cont->block_scantop;
+
+	/* if no bad block checking is possible bail out */
+	if (mtd->block_isbad == NULL)
+		return from;
+
+	/* first time in */
+	if (block_map == NULL) {
+		block_top = mtd->size / mtd->erasesize;
+		block_map = kmalloc(sizeof(*block_map) * block_top, GFP_KERNEL);
+		if (block_map == NULL) {
+			printk (KERN_WARNING "map_over_bad_blocks(): unable to allocate block map\n");
+			return -ENOMEM;
+		}
+		for (i = 0; i < block_top; i++)
+			block_map[i] = -1;
+
+		for (i = 0; i < block_top; i++)
+			if ((*mtd->block_isbad)(mtd, i * mtd->erasesize) == 0)
+				break;
+
+		if (i >= block_top) {
+			printk (KERN_WARNING "map_over_bad_blocks(): all blocks bad!\n");
+			return -EIO;
+		}
+		block_scantop = 0;
+		block_map[0] = i;
+
+		DEBUG(0, "mtd: map %d -> %d\n", block_scantop, block_map[block_scantop]);
+	}
+
+	block = ((int)from / mtd->erasesize);
+	if (block >= block_top)
+		return (loff_t)-1;
+
+	/* scan for bad block up to where we want */
+	while (block >= block_scantop) {
+		/* find a non bad block */
+		for (i = block_map[block_scantop] + 1; i < block_top; i++)
+			if ((*mtd->block_isbad)(mtd, i * mtd->erasesize) == 0)
+				break;
+
+		/* exhausted ? */
+		if (i >= block_top) {
+			printk (KERN_WARNING "map_over_bad_blocks(): no more good blocks!\n");
+			return (loff_t)-1;
+		}
+
+		block_map[++block_scantop] = i;
+		DEBUG(0, "mtd: map %d -> %d\n", block_scantop, block_map[block_scantop]);
+	}
+
+	block = block_map[(int)from / mtd->erasesize];
+	from = (block * mtd->erasesize) | ((int)from & (mtd->erasesize - 1));
+	return from;
+}
+
+static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
+			      unsigned long block, char *buf)
+{
+	size_t retlen;
+	unsigned long from;
+
+	from = map_over_bad_blocks(dev, block<<9);
+
+	if (dev->mtd->read(dev->mtd, from, 512, &retlen, buf))
+		return 1;
+	return 0;
+}
+
+static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
+			      unsigned long block, char *buf)
+{
+	size_t retlen;
+
+	if (dev->mtd->write(dev->mtd, (block * 512), 512, &retlen, buf))
+		return 1;
+	return 0;
+}
+
+static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
+{
+	struct mtd_block_map *dev_cont = kmalloc(sizeof(*dev_cont), GFP_KERNEL);
+
+	if (!dev_cont)
+		return;
+
+	memset(dev_cont, 0, sizeof(*dev_cont));
+
+	dev_cont->dev.mtd = mtd;
+	dev_cont->dev.devnum = mtd->index;
+	dev_cont->dev.blksize = 512;
+	dev_cont->dev.size = mtd->size >> 9;
+	dev_cont->dev.tr = tr;
+	dev_cont->dev.readonly = 1;
+
+	add_mtd_blktrans_dev(&(dev_cont->dev));
+}
+
+static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
+{
+	del_mtd_blktrans_dev(dev);
+	kfree(dev);
+}
+
+static struct mtd_blktrans_ops mtdblock_tr = {
+	.name		= "mtdblock_bbfree",
+	.major		= 258,
+	.part_bits	= 0,
+	.readsect	= mtdblock_readsect,
+	.writesect	= mtdblock_writesect,
+	.add_mtd	= mtdblock_add_mtd,
+	.remove_dev	= mtdblock_remove_dev,
+	.owner		= THIS_MODULE,
+};
+
+static int __init mtdblock_init(void)
+{
+	return register_mtd_blktrans(&mtdblock_tr);
+}
+
+static void __exit mtdblock_exit(void)
+{
+	deregister_mtd_blktrans(&mtdblock_tr);
+}
+
+module_init(mtdblock_init);
+module_exit(mtdblock_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Baydarov Konstantin <kbaidarov@dev.rtsoft.ru>");
+MODULE_DESCRIPTION("Readonly Block Device Layer Over MTD");
Index: mtd-2.6/drivers/mtd/Makefile
===================================================================
--- mtd-2.6.orig/drivers/mtd/Makefile
+++ mtd-2.6/drivers/mtd/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_MTD_AFS_PARTS)	+= afs.o
 obj-$(CONFIG_MTD_CHAR)		+= mtdchar.o
 obj-$(CONFIG_MTD_BLOCK)		+= mtdblock.o mtd_blkdevs.o
 obj-$(CONFIG_MTD_BLOCK_RO)	+= mtdblock_ro.o mtd_blkdevs.o
+obj-$(CONFIG_MTD_BLOCK_RO_BBFREE)	+= mtdblock_ro_bbfree.o mtd_blkdevs.o
 obj-$(CONFIG_FTL)		+= ftl.o mtd_blkdevs.o
 obj-$(CONFIG_NFTL)		+= nftl.o mtd_blkdevs.o
 obj-$(CONFIG_INFTL)		+= inftl.o mtd_blkdevs.o
Index: mtd-2.6/drivers/mtd/Kconfig
===================================================================
--- mtd-2.6.orig/drivers/mtd/Kconfig
+++ mtd-2.6/drivers/mtd/Kconfig
@@ -197,6 +197,13 @@ config MTD_BLOCK_RO
 	  You do not need this option for use with the DiskOnChip devices. For
 	  those, enable NFTL support (CONFIG_NFTL) instead.
 
+config MTD_BLOCK_RO_BBFREE
+	tristate "Readonly bad block free block device access to MTD devices"
+	depends on MTD_BLOCK!=y && MTD
+	help
+	  Same as readonly block driver, but this allow you to mount read-only file
+	  systems from an MTD device, containing bad blocks.
+
 config FTL
 	tristate "FTL (Flash Translation Layer) support"
 	depends on MTD && BLOCK

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Konstantin Baydarov]

On Wed, 22 Nov 2006 19:56:33 +0300
Konstantin Baydarov <kbaidarov@dev.rtsoft.ru> wrote:
> 
> Corrected typo, renamed driver, got rid from redundant dependency.
> Also I've tested mtdblock_ro_bbfree as module - ok.

Renamed driver to 'romblock'. Every entry of 'mtdblock' was replaced.
Debug level in DEBUG macros was replaced by corresponding macros.

 drivers/mtd/Kconfig    |    7 ++
 drivers/mtd/Makefile   |    1 
 drivers/mtd/romblock.c |  165 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 173 insertions(+)

Index: mtd-2.6/drivers/mtd/romblock.c
===================================================================
--- /dev/null
+++ mtd-2.6/drivers/mtd/romblock.c
@@ -0,0 +1,165 @@
+/*
+ *  Readonly Block Device Layer Over MTD
+ *
+ *  (C) 2006 Baydarov Konstantin <kbaidarov@dev.rtsoft.ru>
+ *           Pantelis Antoniou <panto@intracom.gr>
+ *           David Woodhouse <dwmw2@infradead.org>
+ *
+ *  It allows to use any filesystem on this device in
+ *  RO mode and thus gain faster mount times and better
+ *  throughput rates.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/blktrans.h>
+
+struct romblock_map {
+	struct mtd_blktrans_dev dev;
+	/* block map for RO */
+	int32_t *block_map;
+	int32_t block_top;
+	int32_t block_scantop;
+};
+
+static loff_t map_over_bad_blocks(struct mtd_blktrans_dev* dev, loff_t from)
+{
+	int i, block;
+	struct mtd_info *mtd = dev->mtd;
+	struct romblock_map* dev_cont = container_of(dev, struct romblock_map, dev);
+	int32_t *block_map = dev_cont->block_map;
+	int32_t block_top = dev_cont->block_top;
+	int32_t block_scantop = dev_cont->block_scantop;
+
+	/* if no bad block checking is possible bail out */
+	if (mtd->block_isbad == NULL)
+		return from;
+
+	/* first time in */
+	if (block_map == NULL) {
+		block_top = mtd->size / mtd->erasesize;
+		block_map = kmalloc(sizeof(*block_map) * block_top, GFP_KERNEL);
+		if (block_map == NULL) {
+			printk (KERN_ERR "map_over_bad_blocks(): unable to allocate block map\n");
+			return -ENOMEM;
+		}
+		for (i = 0; i < block_top; i++)
+			block_map[i] = -1;
+
+		for (i = 0; i < block_top; i++)
+			if ((*mtd->block_isbad)(mtd, i * mtd->erasesize) == 0)
+				break;
+
+		if (i >= block_top) {
+			printk (KERN_WARNING "map_over_bad_blocks(): all blocks bad!\n");
+			return -EIO;
+		}
+		block_scantop = 0;
+		block_map[0] = i;
+
+		DEBUG(MTD_DEBUG_LEVEL0, "mtd: map %d -> %d\n", block_scantop, block_map[block_scantop]);
+	}
+
+	block = ((int)from / mtd->erasesize);
+	if (block >= block_top)
+		return (loff_t)-1;
+
+	/* scan for bad block up to where we want */
+	while (block >= block_scantop) {
+		/* find a non bad block */
+		for (i = block_map[block_scantop] + 1; i < block_top; i++)
+			if ((*mtd->block_isbad)(mtd, i * mtd->erasesize) == 0)
+				break;
+
+		/* exhausted ? */
+		if (i >= block_top) {
+			printk (KERN_WARNING "map_over_bad_blocks(): no more good blocks!\n");
+			return (loff_t)-1;
+		}
+
+		block_map[++block_scantop] = i;
+		DEBUG(MTD_DEBUG_LEVEL0, "mtd: map %d -> %d\n", block_scantop, block_map[block_scantop]);
+	}
+
+	block = block_map[(int)from / mtd->erasesize];
+	from = (block * mtd->erasesize) | ((int)from & (mtd->erasesize - 1));
+	return from;
+}
+
+static int romblock_readsect(struct mtd_blktrans_dev *dev,
+			      unsigned long block, char *buf)
+{
+	size_t retlen;
+	unsigned long from;
+
+	from = map_over_bad_blocks(dev, block<<9);
+
+	if (dev->mtd->read(dev->mtd, from, 512, &retlen, buf))
+		return 1;
+	return 0;
+}
+
+static int romblock_writesect(struct mtd_blktrans_dev *dev,
+			      unsigned long block, char *buf)
+{
+	size_t retlen;
+
+	if (dev->mtd->write(dev->mtd, (block * 512), 512, &retlen, buf))
+		return 1;
+	return 0;
+}
+
+static void romblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
+{
+	struct romblock_map *dev_cont = kmalloc(sizeof(*dev_cont), GFP_KERNEL);
+
+	if (!dev_cont)
+		return;
+
+	memset(dev_cont, 0, sizeof(*dev_cont));
+
+	dev_cont->dev.mtd = mtd;
+	dev_cont->dev.devnum = mtd->index;
+	dev_cont->dev.blksize = 512;
+	dev_cont->dev.size = mtd->size >> 9;
+	dev_cont->dev.tr = tr;
+	dev_cont->dev.readonly = 1;
+
+	add_mtd_blktrans_dev(&(dev_cont->dev));
+}
+
+static void romblock_remove_dev(struct mtd_blktrans_dev *dev)
+{
+	del_mtd_blktrans_dev(dev);
+	kfree(dev);
+}
+
+static struct mtd_blktrans_ops romblock_tr = {
+	.name		= "romblock",
+	.major		= 258,
+	.part_bits	= 0,
+	.readsect	= romblock_readsect,
+	.writesect	= romblock_writesect,
+	.add_mtd	= romblock_add_mtd,
+	.remove_dev	= romblock_remove_dev,
+	.owner		= THIS_MODULE,
+};
+
+static int __init romblock_init(void)
+{
+	return register_mtd_blktrans(&romblock_tr);
+}
+
+static void __exit romblock_exit(void)
+{
+	deregister_mtd_blktrans(&romblock_tr);
+}
+
+module_init(romblock_init);
+module_exit(romblock_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Baydarov Konstantin <kbaidarov@dev.rtsoft.ru>");
+MODULE_DESCRIPTION("Readonly Block Device Layer Over MTD");
Index: mtd-2.6/drivers/mtd/Makefile
===================================================================
--- mtd-2.6.orig/drivers/mtd/Makefile
+++ mtd-2.6/drivers/mtd/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_MTD_AFS_PARTS)	+= afs.o
 obj-$(CONFIG_MTD_CHAR)		+= mtdchar.o
 obj-$(CONFIG_MTD_BLOCK)		+= mtdblock.o mtd_blkdevs.o
 obj-$(CONFIG_MTD_BLOCK_RO)	+= mtdblock_ro.o mtd_blkdevs.o
+obj-$(CONFIG_MTD_BLOCK_ROMBLOCK)	+= romblock.o mtd_blkdevs.o
 obj-$(CONFIG_FTL)		+= ftl.o mtd_blkdevs.o
 obj-$(CONFIG_NFTL)		+= nftl.o mtd_blkdevs.o
 obj-$(CONFIG_INFTL)		+= inftl.o mtd_blkdevs.o
Index: mtd-2.6/drivers/mtd/Kconfig
===================================================================
--- mtd-2.6.orig/drivers/mtd/Kconfig
+++ mtd-2.6/drivers/mtd/Kconfig
@@ -197,6 +197,13 @@ config MTD_BLOCK_RO
 	  You do not need this option for use with the DiskOnChip devices. For
 	  those, enable NFTL support (CONFIG_NFTL) instead.
 
+config MTD_BLOCK_ROMBLOCK
+	tristate "Readonly Block Device Layer Over MTD"
+	depends on MTD_BLOCK!=y && MTD
+	help
+	  Same as readonly block driver, but this allow you to mount read-only file
+	  systems from an MTD device, containing bad blocks.
+
 config FTL
 	tristate "FTL (Flash Translation Layer) support"
 	depends on MTD && BLOCK

Re: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD

[Gregory CLEMENT]

Hi,
this drivers seems pretty good and easily reviewable, so why it hadn't
been included in mtd tree ?

After some search I had not find any news on this patch, but maybe I
missed something.


2006/12/2, Konstantin Baydarov <kbaidarov@dev.rtsoft.ru>:
> On Wed, 22 Nov 2006 19:56:33 +0300
> Konstantin Baydarov <kbaidarov@dev.rtsoft.ru> wrote:
> >
> > Corrected typo, renamed driver, got rid from redundant dependency.
> > Also I've tested mtdblock_ro_bbfree as module - ok.
>
> Renamed driver to 'romblock'. Every entry of 'mtdblock' was replaced.
> Debug level in DEBUG macros was replaced by corresponding macros.
>
>  drivers/mtd/Kconfig    |    7 ++
>  drivers/mtd/Makefile   |    1
>  drivers/mtd/romblock.c |  165 +++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 173 insertions(+)
>
> Index: mtd-2.6/drivers/mtd/romblock.c
> ===================================================================
> --- /dev/null
> +++ mtd-2.6/drivers/mtd/romblock.c
> @@ -0,0 +1,165 @@
> +/*
> + *  Readonly Block Device Layer Over MTD
> + *
> + *  (C) 2006 Baydarov Konstantin <kbaidarov@dev.rtsoft.ru>
> + *           Pantelis Antoniou <panto@intracom.gr>
> + *           David Woodhouse <dwmw2@infradead.org>
> + *
> + *  It allows to use any filesystem on this device in
> + *  RO mode and thus gain faster mount times and better
> + *  throughput rates.
> + *
> + */
> +
> +#include <linux/init.h>
> +#include <linux/slab.h>
> +#include <linux/mtd/mtd.h>
> +#include <linux/mtd/blktrans.h>
> +
> +struct romblock_map {
> +       struct mtd_blktrans_dev dev;
> +       /* block map for RO */
> +       int32_t *block_map;
> +       int32_t block_top;
> +       int32_t block_scantop;
> +};
> +
> +static loff_t map_over_bad_blocks(struct mtd_blktrans_dev* dev, loff_t from)
> +{
> +       int i, block;
> +       struct mtd_info *mtd = dev->mtd;
> +       struct romblock_map* dev_cont = container_of(dev, struct romblock_map, dev);
> +       int32_t *block_map = dev_cont->block_map;
> +       int32_t block_top = dev_cont->block_top;
> +       int32_t block_scantop = dev_cont->block_scantop;
> +
> +       /* if no bad block checking is possible bail out */
> +       if (mtd->block_isbad == NULL)
> +               return from;
> +
> +       /* first time in */
> +       if (block_map == NULL) {
> +               block_top = mtd->size / mtd->erasesize;
> +               block_map = kmalloc(sizeof(*block_map) * block_top, GFP_KERNEL);
> +               if (block_map == NULL) {
> +                       printk (KERN_ERR "map_over_bad_blocks(): unable to allocate block map\n");
> +                       return -ENOMEM;
> +               }
> +               for (i = 0; i < block_top; i++)
> +                       block_map[i] = -1;
> +
> +               for (i = 0; i < block_top; i++)
> +                       if ((*mtd->block_isbad)(mtd, i * mtd->erasesize) == 0)
> +                               break;
> +
> +               if (i >= block_top) {
> +                       printk (KERN_WARNING "map_over_bad_blocks(): all blocks bad!\n");
> +                       return -EIO;
> +               }
> +               block_scantop = 0;
> +               block_map[0] = i;
> +
> +               DEBUG(MTD_DEBUG_LEVEL0, "mtd: map %d -> %d\n", block_scantop, block_map[block_scantop]);
> +       }
> +
> +       block = ((int)from / mtd->erasesize);
> +       if (block >= block_top)
> +               return (loff_t)-1;
> +
> +       /* scan for bad block up to where we want */
> +       while (block >= block_scantop) {
> +               /* find a non bad block */
> +               for (i = block_map[block_scantop] + 1; i < block_top; i++)
> +                       if ((*mtd->block_isbad)(mtd, i * mtd->erasesize) == 0)
> +                               break;
> +
> +               /* exhausted ? */
> +               if (i >= block_top) {
> +                       printk (KERN_WARNING "map_over_bad_blocks(): no more good blocks!\n");
> +                       return (loff_t)-1;
> +               }
> +
> +               block_map[++block_scantop] = i;
> +               DEBUG(MTD_DEBUG_LEVEL0, "mtd: map %d -> %d\n", block_scantop, block_map[block_scantop]);
> +       }
> +
> +       block = block_map[(int)from / mtd->erasesize];
> +       from = (block * mtd->erasesize) | ((int)from & (mtd->erasesize - 1));
> +       return from;
> +}
> +
> +static int romblock_readsect(struct mtd_blktrans_dev *dev,
> +                             unsigned long block, char *buf)
> +{
> +       size_t retlen;
> +       unsigned long from;
> +
> +       from = map_over_bad_blocks(dev, block<<9);
> +
> +       if (dev->mtd->read(dev->mtd, from, 512, &retlen, buf))
> +               return 1;
> +       return 0;
> +}
> +
> +static int romblock_writesect(struct mtd_blktrans_dev *dev,
> +                             unsigned long block, char *buf)
> +{
> +       size_t retlen;
> +
> +       if (dev->mtd->write(dev->mtd, (block * 512), 512, &retlen, buf))
> +               return 1;
> +       return 0;
> +}
> +
> +static void romblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
> +{
> +       struct romblock_map *dev_cont = kmalloc(sizeof(*dev_cont), GFP_KERNEL);
> +
> +       if (!dev_cont)
> +               return;
> +
> +       memset(dev_cont, 0, sizeof(*dev_cont));
> +
> +       dev_cont->dev.mtd = mtd;
> +       dev_cont->dev.devnum = mtd->index;
> +       dev_cont->dev.blksize = 512;
> +       dev_cont->dev.size = mtd->size >> 9;
> +       dev_cont->dev.tr = tr;
> +       dev_cont->dev.readonly = 1;
> +
> +       add_mtd_blktrans_dev(&(dev_cont->dev));
> +}
> +
> +static void romblock_remove_dev(struct mtd_blktrans_dev *dev)
> +{
> +       del_mtd_blktrans_dev(dev);
> +       kfree(dev);
> +}
> +
> +static struct mtd_blktrans_ops romblock_tr = {
> +       .name           = "romblock",
> +       .major          = 258,
> +       .part_bits      = 0,
> +       .readsect       = romblock_readsect,
> +       .writesect      = romblock_writesect,
> +       .add_mtd        = romblock_add_mtd,
> +       .remove_dev     = romblock_remove_dev,
> +       .owner          = THIS_MODULE,
> +};
> +
> +static int __init romblock_init(void)
> +{
> +       return register_mtd_blktrans(&romblock_tr);
> +}
> +
> +static void __exit romblock_exit(void)
> +{
> +       deregister_mtd_blktrans(&romblock_tr);
> +}
> +
> +module_init(romblock_init);
> +module_exit(romblock_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Baydarov Konstantin <kbaidarov@dev.rtsoft.ru>");
> +MODULE_DESCRIPTION("Readonly Block Device Layer Over MTD");
> Index: mtd-2.6/drivers/mtd/Makefile
> ===================================================================
> --- mtd-2.6.orig/drivers/mtd/Makefile
> +++ mtd-2.6/drivers/mtd/Makefile
> @@ -17,6 +17,7 @@ obj-$(CONFIG_MTD_AFS_PARTS)   += afs.o
>  obj-$(CONFIG_MTD_CHAR)         += mtdchar.o
>  obj-$(CONFIG_MTD_BLOCK)                += mtdblock.o mtd_blkdevs.o
>  obj-$(CONFIG_MTD_BLOCK_RO)     += mtdblock_ro.o mtd_blkdevs.o
> +obj-$(CONFIG_MTD_BLOCK_ROMBLOCK)       += romblock.o mtd_blkdevs.o
>  obj-$(CONFIG_FTL)              += ftl.o mtd_blkdevs.o
>  obj-$(CONFIG_NFTL)             += nftl.o mtd_blkdevs.o
>  obj-$(CONFIG_INFTL)            += inftl.o mtd_blkdevs.o
> Index: mtd-2.6/drivers/mtd/Kconfig
> ===================================================================
> --- mtd-2.6.orig/drivers/mtd/Kconfig
> +++ mtd-2.6/drivers/mtd/Kconfig
> @@ -197,6 +197,13 @@ config MTD_BLOCK_RO
>           You do not need this option for use with the DiskOnChip devices. For
>           those, enable NFTL support (CONFIG_NFTL) instead.
>
> +config MTD_BLOCK_ROMBLOCK
> +       tristate "Readonly Block Device Layer Over MTD"
> +       depends on MTD_BLOCK!=y && MTD
> +       help
> +         Same as readonly block driver, but this allow you to mount read-only file
> +         systems from an MTD device, containing bad blocks.
> +
>  config FTL
>         tristate "FTL (Flash Translation Layer) support"
>         depends on MTD && BLOCK
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>


-- 
Gregory CLEMENT
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