How to erase mtdblock in C program?

Sarick a écrit :

Hi

Which file system do you use? Personnaly I use a JFFS2 file system for my flash file system, and I am not worried about erasing flash before writing, it' s manage by the jffs2, so when I want to write a root jffs2 file system image to mtdblock in c I use the binary dd or cat like that: system("cat /tmp/myJFFS2RootImage.img > /dev/mtdblock3");

In my case once there is a JFFS2 file system in the mtdblock, even if the root file system grow, the erase and write is manage by jffs2, so you you write and read as simple as an ext3 or fat32 file system on a hard disk with your OS.

I' m interesting about how proceed others?

Pes

There are erase and eraseall commands included in the MTD distribution, grab the latest version from the linux-mtd homepage. Erasure of MTD devices is achieved using ioctl() calls.

FWIW, flashing an actual filesystem onto your mtdblock devices defeats the purpose of using a wear levelling filesystem. Instead you should delete the old files and replace them with the new ones.

Instead of generating a filesystem, try simply copying the actual files onto your board.

Hi,

I tried using ioctl(), but fail to get mtd info through the MEMGETINFO i/o command. The strerror result is: "Inappropriate ioctl for device". I checked both the file descriptor and MEMGETINFO value, the fd is valid, while the MEMGETINFO has a strange value (-2145366783). Does anyone know this problem?

The reason that I cannot use 'cat' command to copy to the mtdblock is that, I am using network downloading to get the new fs image. The filesystem image is downloaded via tftp, which receives as separated packets. And I have to write each received block into FS2 immediately since the buffer size isn't big enough for whole image. The only one way I knew is to write() to the mtdblock directly. But is there any other appropriate ways for my purpose?

Further that, I tried using write() to write to mtdblock(FS2), and write() the rest bytes to '0xff' for unused purpose. But I'm getting error messages like this:

MTD do_write_oneword(): Wacky! Unable to decode failure status Possible buggy device - try enabling CONFIG_MTD_CFI_AMDSTD_RETRY in your kernel config and setting driver retry_cmd_max MTD do_write_oneword(): 0x005419ac(0x00001985): 0x0000ffff 0x0000ffff

Anyone know why?

Thanks Sarick

Hi Pes,

I'm using JFFS2 as my file system. But still having the ioctl problem as I described in my previous mail. Any help would be very appreciative.

Sarick

Sarick a écrit :

Hi,

According to Geronimo, I' ve ommit to say that I do a "eraseall /dev/mtdX" to erase /dev/mtdblockX before writing a file system. I' m sorry I don' t know how to use the ioctl interface but maybe, if you don' t find a better solution and if you haven' t enough memory, you could separate your root file system in several little files and generate something like that in c: dd if=temp.bin of=/dev/mtdblock0 bs=512 count=1 dd if=temp.bin of=/dev/mtdblock0 bs=512 count=1 seek=1 dd if=temp.bin of=/dev/mtdblock0 bs=512 count=1 seek=2 ...

Sounds like the incorrect data type is being used.

If you have the source to erase.c and eraseall.c, you should be able to compile those on your system and confirm that they work correctly (they work just fine for me and I guess everyone else who uses MTD). So you are doing something wrong in your code.

I would suggest that the data you are storing be kept in a tar file, which you unpack onto your flash mount once you have downloaded it. By programming the image directly you are bypassing the wear-levelling features of JFFS2. There is almost no point in using JFFS2 if you do not need wear-levelling.

I think you do not understand how flash devices work; I suggest you Google for some documentation or read the data sheet of your flash device. Writing 0xFF to a flash address does not erase it. The flash chip requires that you execute a separate erase command on the sector which is to be cleared. To do that, you need to use the MTD ioctl.

Once data is written in a flash sector it cannot be rewritten, the sector must be erased first.