Re: [Libmtp-discuss] SanDisk Sansa View connection problem

[Linus W. <lin...@gm...>]

2008/2/11, Sciamano <sci...@gm...>:

> Anyway, my intentions with the first post was to point out "this"
> connection problem, in case it was useful for improving libmtp.

Yeah, well not perhaps libmtp as it is but maybe something generic
can be done to ease the situation if it is as I suspect. The problem
is we don't know for sure why the device behaves like this, I only have
an educated guess.

If I am right the MTP protocol itself is not the problem, the problem
is how the devices are made. They are all built to be used by one
GUI thing, the Windows Media Player. Anything that behaves
differently will be untested.

So to behave like the device want you to, you have to be a GUI
sufficiently like WMP. And I think gnomad2, Amarok 2 (KDE4 choice!)
and Rhythmbox (GNOME choice!) are getting close to that.
The achieve it using HAL and D-Bus to "hook" the device the
instant it appears.

(It's too bad for those who like command-line utilities though,
then again, not all devices have this problem.)

The problem is that on Windows, there is a daemon that "hook"
the device when you plug it in (or boot with it plugged) and keep
it hooked until you plug it out or shut down the host. The device
expects to be "hooked" and thus will revert to something like
USB mass storage mode or plain reset unless it gets hooked
quick enough. This problem is very common I think. Some devices
do not even allow for closing the PTP/MTP session without
causing USB errors, this is a protocol violation but the manufacturers
doesn't seem to care.

It has been suggested to create a generic daemon that "hook"
devices when they are plugged-in, and maintain a session with them
until they are unplugged. (This is what Windows does, I think).
This can be written around libmtp if we make a few changes to
it. It's a lot of work and require all software using libmtp (including
any command-line utilities) to be modified to use that as session
manager. And it is not likely to happen, IMHO.

BTW: Richard, do you have anything for the Mac sortalike
HAL+D-Bus that can notify XNJB when new devices are plugged
in so you can hook them?

Linus