[RFC] [PATCH] [MTD-UTILS]: flash_lock: fix length being passed

[Vimal Singh]

On Fri, Dec 4, 2009 at 2:11 PM, Artem Bityutskiy <dedekind1 at gmail.com> wrote:
> On Wed, 2009-12-02 at 19:58 +0530, Vimal Singh wrote:
>> This patch fixes the 'length' calculation.
>> Making it:
>> +       mtdLockInfo.length = (num_sectors - 1) * mtdInfo.erasesize;
>> Rather:
>> -       mtdLockInfo.length = num_sectors * mtdInfo.erasesize;
>>
>> Say there are 240 blocks present in the device. Then:
>> offset starts from: 0x0
>> and full size of device: 0x1E00000
>>
>> doing: 240 * 0x20000 gives -> 0x1E00000
>> But last block address should be 0x1DE0000 (which spans for 0x20000
>> bytes, adding upto size of 0x1E00000)
>>
>> Signed-off-by: Vimal Singh <vimalsingh at ti.com>
>> ---
>>
>> --- flash_lock.c.org  2009-11-24 19:33:18.000000000 +0530
>> +++ flash_lock.c      2009-11-24 19:33:13.000000000 +0530
>> @@ -71,7 +71,7 @@ int main(int argc, char *argv[])
>>       }
>>
>>       mtdLockInfo.start = ofs;
>> -     mtdLockInfo.length = num_sectors * mtdInfo.erasesize;
>> +     mtdLockInfo.length = (num_sectors - 1) * mtdInfo.erasesize;
>>       if(ioctl(fd, MEMLOCK, &mtdLockInfo))
>>       {
>>               fprintf(stderr, "Could not lock MTD device: %s\n", argv[1]);
>> @@ -81,4 +81,3 @@ int main(int argc, char *argv[])
>
> So if num_sectors is 1, mtdLockInfo.length is 0 - is it expected?

I think so. Suppose you want to lock 1st block: 'start' will be '0x0' and
if you pass 'length' as one block size then boundaries will be:

start: 0x0 ('0'th block)
end: 0x20000 (1st block)        if 0x20000 is the block size

so you will lock 2 blocks here.

While passing 'length' as '0' for this case will lock only 1st block
(0th block).

-- 
Regards,
Vimal Singh