maemo.org - Talk - Editing n900's rootfs.jffs2

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- - Editing n900's rootfs.jffs2 (https://talk.maemo.org/showthread.php?t=35554)

Re: Editing n900's rootfs.jffs2

writing to mtd with dd is prone to fail, as dd doesn't know about bad block management in mtd, and mtd is a *raw* device where you eventually will run into an occasional bad block.

There are tools that are specifically built to deal with bad blocks on mtd, e.g mtd_debug is one of them I'd assume, available in fremantle.

/j

Re: Editing n900's rootfs.jffs2

Correct way how to erase/flash rootfs partition (on which is ubi) is to use ubiformat utility.

Before using ubiformat utility, first any mounted ubifs volume must be umounted and ubi device deattached from mtd partition.

Code:

$ umount ubi:rootfs

$ ubidetach /dev/ubi_ctrl -d 0

Erasing mtd partition on with is ubi:

Code:

$ ubiformat /dev/<mtd_rootfs>

Erasing & Flashing new ubi image (with volumes) on mtd partition:

Code:

$ ubiformat /dev/<mtd_rootfs> -s 512 -O 512 -f <image.ubi>

After flashing new ubi image to mtd, ubi can be attached to mtd device again:

Code:

$ ubiattach /dev/ubi_ctrl -p /dev/<mtd_rootfs>

And then available ubifs volume in ubi can be mounted

Code:

$ mount ubi:rootfs </mountpoint> -t ubifs

Re: Editing n900's rootfs.jffs2

So correct way how to mount N900 rootfs on computer using nandsim is:
(this will use ubiformat instead mtdblock and dd as in #3rd post)

1. Load nandsim module (which emulate nand mtd device) with same layout as has N900:

Code:

$ modprobe nandsim first_id_byte=0x20 second_id_byte=0xaa third_id_byte=0x00 fourth_id_byte=0x15 parts=1,3,2,16,16,2010

2. Load ubi and ubifs modules:

Code:

$ modprobe ubi

$ modprobe ubifs

3. Flash rootfs ubi image to emulated nand mtd device:

Code:

$ ubiformat /dev/mtd5 -s 512 -O 512 -f <rootfs_image>

4. Attach mtd device to ubi:

Code:

$ ubiattach /dev/ubi_ctrl -p /dev/mtd5

5. Mount rootfs volume (ubifs image) from ubi to /mnt/n900:

Code:

$ mkdir -p /mnt/n900

$ mount ubi:rootfs /mnt/n900 -t ubifs

And then rootfs image should be mounted to /mnt/n900

Umounting & cleaning:

Code:

$ umount /mnt/n900

$ ubidetach /dev/ubi_ctrl -d 0

$ rmmod ubifs

$ rmmod ubi

$ rmmod nandsim

Re: Editing n900's rootfs.jffs2

Original Maemo 5 rootfs UBI image was generated with 1870 UBI LEBs for rootfs UBIFS volume, which correspond to 230MiB (=1870*126KiB). Therefore correction for #3rd post of cfg.ini:

Code:

[rootfs]

mode=ubi

image=rootfs_ubifs.jffs2

vol_id=0

vol_size=230MiB

vol_type=dynamic

vol_name=rootfs

vol_flags=autoresize

vol_alignment=1

Re: Editing n900's rootfs.jffs2

Oh $#!T it's Pali!!! OY! it has been a long time!
(edit)since 2019!!

Re: Editing n900's rootfs.jffs2

I think it can be useful also for others with other devices, so here is guide how to properly generate UBI image with UBIFS volume for any MTD device. Both mkfs.ubifs and ubinize tools needs to know geometry of target MTD device (e.g. NAND) during creating of images. The best way how to detect all required parameters is to install mtdinfo utility on target system and run it with -u option for target MTD device. Also optimal value of $MAX_LEB_CNT depends on kernel config option CONFIG_MTD_UBI_BEB_LIMIT.

Here are all commands how to determinate and calculate all required parameters for target MTD device /dev/mtd0:

PEB_SIZE <-- mtdinfo /dev/mtd0 -u | sed -n 's/^Eraseblock size: *$[^ ]*$.*/\1/p'
LEB_SIZE <-- mtdinfo /dev/mtd0 -u | sed -n 's/^Default UBI LEB size: *$[^ ]*$.*/\1/p'
MIN_IO_SIZE <-- mtdinfo /dev/mtd0 -u | sed -n 's/^Minimum input\/output unit size: *$[^ ]*$.*/\1/p'
SUB_PAGE_SIZE <-- mtdinfo /dev/mtd0 -u | sed -n 's/^Sub-page size: *$[^ ]*$.*/\1/p'
EB_CNT <-- mtdinfo /dev/mtd0 -u | sed -n 's/^Amount of eraseblocks: *$[^ ]*$.*/\1/p'
BEB_LIMIT <-- gunzip -c /proc/config.gz | sed -n 's/^CONFIG_MTD_UBI_BEB_LIMIT=//p'
BEB_CNT <-- $BEB_LIMIT * $EB_CNT / 1000
MAX_LEB_CNT <-- (($EB_CNT * $PEB_SIZE) - (($BEB_CNT + 4) * $PEB_SIZE + ($PEB_SIZE - $LEB_SIZE) * ($EB_CNT - $BEB_CNT - 4))) / $LEB_SIZE
VOL_SIZE <-- Size of the generated UBIFS image file ubifs.img (minimal value)
VOL_NAME <-- Name of UBI volume for UBIFS image (e.g. "rootfs")

Calculation of $MAX_LEB_CNT is done according to official information in UBI documentation at:
http://www.linux-mtd.infradead.org/d...tml#L_overhead
Maximal number (but not larger than $MAX_LEB_CNT) for currenly attached UBI volume can be read from file:
/sys/class/ubi/ubi0_0/reserved_ebs. So it can be used for verification that $MAX_LEB_CNT was calculated optimally. Note that bad blocks on device cause lower value.

UBI image ubi.img with UBIFS volume with content of $ROOT_DIR can be generated via following commands:

Code:

/usr/sbin/mkfs.ubifs -m $MIN_IO_SIZE -e $LEB_SIZE -c $MAX_LEB_CNT -r $ROOT_DIR ubifs.img



cat > cfg.ini << EOF

[$VOL_NAME]

mode=ubi

image=ubifs.img

vol_id=0

vol_size=$VOL_SIZE

vol_type=dynamic

vol_name=$VOL_NAME

vol_flags=autoresize

vol_alignment=1

EOF



/usr/sbin/ubinize -o ubi.img -p $PEB_SIZE -m $MIN_IO_SIZE -s $SUB_PAGE_SIZE cfg.ini

Line vol_size= in cfg.ini can be omitted and ubinize will then calculate size from ubifs.img file.

For /dev/mtd5 partition in Nokia N900 with Maemo 2.6.28 kernel are following optimal/correct values:

PEB_SIZE=131072
LEB_SIZE=129024
MIN_IO_SIZE=2048
SUB_PAGE_SIZE=512
MAX_LEB_CNT=1986

As can be seen in examples, mkfs.ubifs was called by Nokia with -c option MAX_LEB_CNT=2047, but maximal value is just 1986. On my N900, kernel reports in /sys/class/ubi/ubi0_0/reserved_ebs value 1985 which proves that calculation is correct (value is smaller probably due to already bad blocks).

Re: Editing n900's rootfs.jffs2

Just awesome you are here and share this info!