We end up using the FIT file name as the "fingerprint" for the dive, and
include it at the beginning of the dive data as such. And because of
how Garmin encoded the FIT files, we ended up having a fixed 24-byte
length for this, which is normally the date encoding:
YYYY-MM-DD-HH-MM-SS.FIT
with the terminating NUL character.
Of course, then Garmin started using a short-form encoding too
(presumably due to FAT filesystem limits), and we have magic code to
sort the dates properly, using the name format
YMDHMMSS.FIT
with the numbers encoded in a shorter format (eg "C4ND0302.fit" is
equivalent to "2022-04-23-13-03-02.fit"). See name_cmp() and
parse_short_name() for details.
Anyway, because we use the (zero-padded) 24 characters of the name as
the fingerprint, we used a fixed-size buffer for the filename that was
limited to that maximum size Garmin creates.
But then you download those things, and have multiple vendors, and
suddenly that 24-character limit on the filename is very annoying.
Instead of fixing this in some clean and generic way, let's just raise
the namelength limit to something bigger, and continue to use the first
24 characters of the name for the fingerprint.
Pretty it isn't, but it makes it slightly easier to import random FIT
files that don't conform exactly to the traditional Garmin format.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Create parallel helper functions that use libmtp to walk the file tree on the
device and to then read a specific file from the device into our dc_buffer.
MTP is not a file system, it's an object storage, that just happens to allow
object names and parent/child relationships between objects. As a result we
need to remember those file ids for MTP downloads.
The mtp_get_file_list function is rather complex as it includes both the
initial communication with the device and the code to walk the object tree and
then create the list of file.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
We do this for a few other device where we need slightly different behavior,
depending on the specific model.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This uses pretty much all of our new infrastructure: the USB storage
iostream for the actual IO, the field-cache for the divecomputer fields,
and the string interface for the events.
It's also a very fast downloader.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
