Re: Removing Cell Modem

[Dan Williams <dcbw redhat com>]

On Wed, 2010-06-23 at 13:13 -0400, Stuart D. Gathman wrote:
> We recently purchased a Cricket Cell modem, and it was supported perfectly 
> out of the box by NetworkManager on Fedora 12.  Great job!
> 
> My question is this: the tiny "manual" that came with the Cricket warns me 
> not to remove the modem with deactivating it first using an icon on the 
> Windows driver, or "you may damage the device.  What does this mean?  I 
> hate it when these products don't give you any real info.
> 
> I thought of these interpretations:
> 
> 1) The only issue is that the flash drive also presented by the Cricket 
> may get corrupted if removed without unmounting.
> 
> 2) The issue is that no packets should be in flight because the USB 
> implementation on the Cricket is substandard and can't shutdown properly 
> in time on a USB disconnect.
> 
> 3) The warning only applies when using the Y adapter to connect the modem 
> to 2 USB ports (for laptops/netbooks that have insufficient power on a 
> single port).  Perhaps the disconnect negotiations don't work quite right 
> in that case.
> 
> 4) The warning is CYA and bogus.

I would expect that (1) and (3) may be true.  But (2) is not true,
otherwise the OEM that makes the device is an idiot.

> Just in case of (2), I currently shutdown the laptop before disconnecting 
> the modem.
> 
> Does anyone know what the real issue is?  Does NetworkManager need a 
> "safely remove" option like USB storage drives have?

NM probably doesn't need one, but it might make sense to have a
system-wide one for cases where the flash drive thing is an issue. Most
devices have MicroSD card slots these days and yes, pulling them out
without "safely removing" them might corrupt the data on the SD card.
If that functionality was present in the NM UI somewhere, it would
essentially just call out to whatever the file manager (Nautilus or
whatever) does to safely remove or eject the storage medium.  But NM
shouldn't implement it natively.

In the end I think this requires more UI design thought which probably
means talking to design people on the lists for whichever desktop
environment you're using.  Or maybe it just takes user education same as
flash drives do.  Thoughts?

Dan