Trying to read the badblock list / Using MTD devices

[Visti Andresen]

On Sat, 4 Aug 2007 13:45:52 +0200
Visti Andresen <talpa at galnet.dk> wrote:

> Hi I'm trying to create an application that reads Out Of Band information
> from the flash chip.
> The goal being to create an application that can display/backup the
> badblock information from the flash.
> 
> I have had some problems reading correct CRC type values
> (getting illegal values like -1)
> Anso I didn't find any badblocks at all.
> 
> I then discovered that my problems ran deeper that fist expected.
> If I open /dev/mtd0 and close it again the entire flash filesystem returns 
> "Input/output error"
> Took some time to discover this as I was scp'ing to /tmp and things inside the
> disk cache can still be read/executed.
> 
> Below is a small test program that can cause the crash, I compile it using:
> ./build/tmp/cross/arm-linux/bin/gcc -Wall -o mtd_test mtd_test.c 
> 
> Any one know why I get the "Input/output error" after I have executed the 
> program on the Neo?
> 
> Btw. the O_NONBLOCK option was something I picked up a some web page 
> claiming that otherwise the result would not be as expected.
> Removing it gives the same behaviour.
> 
> The output of the program is:
> root at fic-gta01:~$ ./mtd_test 
> Opened MTD device /dev/mtd0 OK
> Closed MTD device /dev/mtd0 OK
> 
> 
> =====
> 
> #include <stdio.h>
> #include <fcntl.h>
> #include <errno.h>
> #include <stdlib.h>
> #include <string.h>
> #include <unistd.h>
> 
> char verbose_ = 1;
> 
> void test(char *mtdDevice);
> 
> 
> int main()
> {
>   test("/dev/mtd0");
>   return 0;
> }
> 
> void test(char *mtdDevice)
> {
>   int device;
>   
>   device = open(mtdDevice, O_RDONLY|O_NONBLOCK);
>   if (device < 0) {
> 		fprintf(stderr, "Unable to open MTD device %s: %s\n", mtdDevice, strerror(errno));
> 		return;
> 	}
>   else {
>     printf("Opened MTD device %s OK\n", mtdDevice);
>   }
>   
> 
>   if (0!=close(device)){
>     printf("Failed to close MTD device %s: %s\n", mtdDevice, strerror(errno));
>   }
>   else {
>     printf("Closed MTD device %s OK\n", mtdDevice);
>   }
> }
> 

An odd detail if I do a "dd if=/dev/mtd0 of=test.bin bs=512 count=32"
on my Nokia 770 the file system remains operational.

On the Neo1973 this results in a "crashed" file system that returns
"Input/output error"

A BUG in the MTD system?