Should MTD_WRITEABLE be split into MTD_WRITEABLE and MTD_ERASEABLE?

[Mike Frysinger]

On Mon, Sep 22, 2008 at 15:03, Jim Ramsay wrote:
> Currently, MTD partitions that do not begin and end exactly on an erase
> sector boundary are forced to be read-only (The MTD_WRITEABLE flag is
> forcibly removed).  I understand that this is required so that you
> don't try to erase that partition and accidentally blow away other
> information on other partitions that may also share the erase sector.
>
> However, in the case of embedded systems, it can be very useful to
> create a very small MTD partition for a simple write-once facility
> (such as for capturing part of a log file or crash dump), and this
> check makes such a partition impossible - Even if the code that
> actually adds the partition is clever enough to properly erase that
> area of flash before adding it.  There is no technical reason of which
> I am aware that prevents normal mtd_write code from working on a small
> non-erase-aligned partition if it has been previously erased.
>
> So I would suggest that splitting MTD_WRITEABLE into two flags,
> MTD_WRITEABLE and MTD_ERASEABLE would be a good idea.  The current
> check for erase boundaries would then only remove MTD_ERASEABLE, whereas
> MTD_WRITEABLE could still be removed via the mtd_partition.mask_flags
> when required.

if you split it into MTD_ERASEABLE and MTD_APPENDABLE, then you could
keep compatibility with:
#define MTD_WRITABLE (MTD_ERASEABLE | MTD_APPENDABLE)

otherwise you just volunteered to update every single
board/driver/core out there that is using MTD_WRITABLE
-mike