For better or worse, erase in the block device API is intended for flash
erases, which is a low-level operation that must occur before every
write and limits the write size of the underlying blocks. This is
different than the erase size found in SD cards, which does not limit
the write size for blocks.
Following the standard set by ATA and the ioctl function, we are adding
a seperate operation for the SD card erase behaviour named trim.
See for more info:
https://en.wikipedia.org/wiki/Trim_(computing)