C Error Open O_RDWR on Read-Only Flash NAND MTD0

Question

I have made a code that read data from flash Nand (without filesystem).

fd = open("/dev/mtd0", O_RDONLY)

It works, then I want to try to read write it.. So I change the code to:

fd = open("/dev/mtd0", O_RDWR)

But It returns -1, means can not open. But for others MTD, it works.

Then I see cat /proc/mtd said that MTD0 is RO and the other is RW (i think it's Read-Only and Read-Write)

I tried to use MEMUNLOCK

ioctl(fd, MEMUNLOCK, &mtdLockInfo)

Because it needs fd, needs open so i use O_RDONLY not O_RDWR(return -1).

But it returns error Bad file description. It must be because of O_RDONLY,, have to use O_WRONLY or O_RDWR.

Is there any way to UNLOCK this MTD0, or to write on it without unlock it??

Answer 1

I have tried to change the partition of my NAND flash in the Device Tree Source(DTS).

There's an read-only option. But, I only changed their size.

ANd it's done.. My NAND flash can be accessed.

Answer 2

The operation is likely being forbidden by the kernel driver for your device. It's likely that your device is actually read-only or marked as such by the driver.