[PATCH] tools: fw_env: use erasesize from MEMGETINFO ioctl

[Rasmus Villemoes]

On 20/03/2020 15.11, Wolfgang Denk wrote:
> Dear Rasmus,
> 
> In message <20200320140414.19689-1-rasmus.villemoes at prevas.dk> you wrote:
>>
>> Having different fw_env.config files for the different revisions is
>> highly impractical, and the correct information is already available
>> right at our fingertips. So use the erasesize returned by the
>> MEMGETINFO ioctl when the fourth column is absent or contains a 0.
>>
>> As I'm only testing this on a NOR flash, I'm only changing the logic
>> for that case, though I think it should be possible for the other
>> types as well.
>>
>> Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
>> ---
>>  tools/env/fw_env.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c
>> index 381739d28d..87c3504315 100644
>> --- a/tools/env/fw_env.c
>> +++ b/tools/env/fw_env.c
>> @@ -1647,6 +1647,8 @@ static int check_device_config(int dev)
>>  			goto err;
>>  		}
>>  		DEVTYPE(dev) = mtdinfo.type;
>> +		if (DEVESIZE(dev) == 0 && mtdinfo.type == MTD_NORFLASH)
>> +			DEVESIZE(dev) = mtdinfo.erasesize;
>>  		if (DEVESIZE(dev) == 0)
>>  			/* Assume the erase size is the same as the env-size */
>>  			DEVESIZE(dev) = ENVSIZE(dev);
> 
> What happens if you - say - have an environment size of 16 KiB and
> an erase block size of 4 KiB?

The right thing - just as in my test case of an environment of 8K and
erase block size of 4K, ENVSECTORS gets computed as 2 (or 4 in your
example). And if the environment has a size which is not a multiple of
the erase block size, all the same logic as usual applies.

It really works just the same as if one explicitly put in an erase block
size in fw_env.config of 4K, but as I wrote in the commit log, there are
cases where one has to support different flashes with different erase
block sizes.

Now, if somebody has put in 0 for the erase block size (relying on the
env size being used) and a 1 in the ENVSECTORS column, then yes, this
will break. I can certainly add an additional check for ENVSECTORS(dev)
being 0 in order to apply the mtdinfo.erasesize.

Rasmus