Re: [Yaffs] mounting yaffs via mount cmd.

Hello

I have been out of office for the Christmas/New Year period, so please
forgive a delay in answering.

On Sat, Jan 12, 2019 at 6:19 PM Pham, Phong <phamp@ddc-web.com> wrote:

>
>
> Hi,
>
>
>
> I have a Linux newbie filesystem question.
>
>
>
> On Linux command line: mount -t yaffs2 /dev/ram2 /mnt/mtd
>
>
>
> Where ram2 is a block device with major number RAMDISK_MAJOR, then
> yaffs2_mount() is executed. (The consequence is failure but I am not
> interested in the failure.)
>
>
>
> However, when a
>
> mount -t yaffs2 /dev/mydevice /mnt/mtd
>
>
>
> where mydevice is a block device with major number MTD_BLOCK_MAJOR, then
> yaffs2_mount() is not executed. Linux couldn’t find an entry in the
> bdev_map->probe[MTD_BLOCK_MAJOR] (in genhd.c). Is this because I don’t
> have a MTD Chip Driver installed for YAFFS2 MTD “user” module? (I
> currently do not have the driver yet; just experimenting right now.)
>

The mtd "block devices" are a bit of a cheat way to pass access to the mtd
drivers to a flash file system. Yaffs needs flash drivers, not generic
block drivers. Hence, Yaffs will only succeed mounting an mtd block device.

If you want to experiment on a system that does not have flash memory and
an mtd block device, then you can use nandsim instead. This makes a fake
mtd block driver that is backed by memory, but still provides all the mtd
access functions.

For an example of how to do this, have a look in the yaffs2/linux-tests
directory at the initnandsim script.




>
> During initialization, I do see init_mtdblock() is invoked and
> major_names[MTD_BLOCK_MAJOR] is initialized (register_blkdev() is invoked),
> but bdev_map->probe[MTD_BLOCK_MAJOR] is not initialized.
>
>
>
> Advise pls.,
>
> Phong.
>
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