The SCSI driver calls GetCapacity to get the block size and number of
blocks of the underlying block-device/LUN. It caches these values and uses
them later on to verify that reads/writes are within the bounds of the LUN.
But, prior to this commit, there was only one set of cached values for all
LUNs, so the bounds checking for a LUN could use incorrect values, values
from one of the other LUNs that most recently updated the cached values.
This would lead to failed SCSI requests.
This commit fixes this issue by having separate cached values for each LUN.
Signed-off-by: Damien George <damien@micropython.org>
With this the user can select multiple logical units to expose over USB MSC
at once, eg: pyb.usb_mode('VCP+MSC', msc=(pyb.Flash(), pyb.SDCard())). The
default behaviour is the original behaviour of just one unit at a time.
SCSI can support multiple logical units over the one interface (in this
case over USBD MSC) and here the MSC code is reworked to support this
feature. At this point only one LU is used and the behaviour is mostly
unchanged from before, except the INQUIRY result is different (it will
report "Flash" for both flash and SD card).
Damien George