Scott Wood wrote:
Wolfgang Denk wrote:
Dear Scott,
In message 4A39685F.6030304@freescale.com you wrote:
Hmm... perhaps check the alignment? If "end" is supposed to be the last to-be-erased byte, not the first not-to-be-erased byte, then if the low bits are 0 it's a size (and gets a warning) and if they're 1 it's an end?
Stop here. Don't add fancy stuf that nobody expects.
Nobody expects the semantics to silently change...
I'm not particularly advocating this approach, just throwing out alternatives. Leaving it alone is probably best.
Ask yourself what the end user expects - we all think of "erase" preparing the grounds for "write", right?
Sometimes. Other times, it could be preparing for use by a filesystem (which may not use the same bad block handling scheme), to reset the environment, for testing, etc.
We have the plus syntax specifically for the use case of erase+write of a specific number of bytes; IMO that's the place for this kind of interpretation.
So both should work oin the same NAND flash region when given the same arguments (offset and seze,
So then there would be no reliable way of erasing a specific range of flash. To properly use the block-skipping approach, the user needs to have in mind a range of actual blocks that the data can take up (i.e. a maximum number of bad blocks to expect), so that they can avoid locating the next partition within that range. I don't think it makes sense to try to completely hide this.
Perhaps "write" should accept an optional limit argument, returning an error if enough bad blocks were encountered to bust the limit.
no matter how these are specified).
If the syntax were changed to start/end, but the erase could go beyond end anyway, that would be extremely confusing.
-Scott
Summarizing, there are two alternatives:
- change 'erase' command aligning it with 'write' and 'read' command (what the patch does);
- add a third field to the 'erase' command, maybe called 'limit', over which erasing can't be done:
'nand erase start offset limit'
In this case, I think that 'write' command may be aligned with this new syntax too.
It's up to you.
Regards, Michele