Messages in this thread | | | Date | Thu, 01 Jul 2010 13:49:32 +0300 | From | Adrian Hunter <> | Subject | Re: [PATCH V3 1/5] mmc: Add erase, secure erase, trim and secure trim operations |
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Andrew Morton wrote: > On Thu, 24 Jun 2010 11:44:00 +0300 > Adrian Hunter <adrian.hunter@nokia.com> 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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