Andrew Morton wrote:
On Thu, 24 Jun 2010 11:44:00 +0300
Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
SD/MMC cards tend to support an erase operation. In addition,
eMMC v4.4 cards can support secure erase, trim and secure trim
operations that are all variants of the basic erase command.
The patch proposes a new userspace interface via sysfs, yes?
,
Just two read-only values
Please fully describe that interface and its operation in the
changelog. It'd also be nice to add permanent documentation for it.
OK
From reading the code, it appears that erase_size and
preferred_erase_size have units in bytes. But users shouldn't need to
read the code to find that out. What are the alignemnt and size
requirements on these? What is their position in /sys? What do they
actually *do* and what is the difference between them?
etetera. People want to review this code and other people actually
want to use it. I'm not sure that I want to try to review this code
when nobody's told me what interface it implements and how it's
supposed to work. Seems that whoever implemented BLKDISCARD didn't
want anyone to use it either. Sigh.
All of mmc core appears to use 32-bit quantities to represent sectors,
yes? Why didn't it use sector_t? What are the implications of this?
SD/MMC addressing uses 32-bit values. There is a known 2TB limit for
SD/MMC cards. As cards are only just getting to 64GB, that limit is
some way off, and it is not clear NAND technology can get there in
a SD/MMC package anyway.
I don't know why sector_t is not used. I guess it would complicate doing
division since it can be 64-bit.
The implications are minimal. In the unlikely event SD/MMC cards ever
exceed 2TB some changes will be needed, but the standard would have to
change to allow that first.
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