Reattach/redetect allways connected umass device - is it possible ?

Stijn Hoop stijn at
Tue Mar 29 02:52:10 PST 2005

On Tue, Mar 29, 2005 at 08:43:47PM +1000, Peter Jeremy wrote:
> On Tue, 2005-Mar-29 10:16:05 +0200, Stijn Hoop wrote:
> > From a desktop user experience point of view, it is rather nice to get
> > a notification if and when removable media disappears, without
> > continously polling said media.
> There's no reason why the kernel couldn't regularly poll removable media
> as long as it didn't interfere with normal operation of the device or
> intrude upon the user (who remembers Amiga FDD's ticking?).

Powersaving reasons (as has been stated in this thread already, I
believe) come to mind. Or, in some cases, physical wear & tear on the
hardware -- although I believe it's not the case for regular USB flash
drives, I can imagine an implementation that needs to access the
physical media in order to determine status (cardreaders?).

But as Poul-Henning said, it's up to the drivers themselves to resort
to polling if needed.

> > This statement intentionally ignores
> > the question of how to get such an event through the kernel to
> > userspace.
> I don't believe this is a problem.  For a command line interface, you
> run "ls" and get a snapshot of the directory contents - you don't expect
> the output from an old "ls" to magically update itself when a file is
> deleted, you re-run "ls".  GUI file browsers are more of a problem but
> as long as the browser doesn't cache the results from one invocation to
> another, this wouldn't seem to be a problem.

I was not thinking of contents exactly; more of the desktop user
experience where, by inserting an USB drive, an icon appears on the
desktop. That icon should be removed when the drive is removed again.
Other similar usecases abound.

> In any case, the majority of the computer users seem quite happy with
> a user interface that, upon ejecting a removable medium and inserting
> a different medium, will happily display the union of the contents of
> the old and new media.

I might be misreading the sarcasm here, but I for one am not happy
with the mixed contents. I'm already a bit weary of using removable
media with FreeBSD because I'm unsure what works and what does not.
This is a situation I would like to remedy.

> It would take a seriously warped mind to
> manage anything so non-intuitive so anything we achieve will be an
> improvement over the status quo.

That I can agree with.


There are of course many problems connected with life, of which some of
the most popular are 'Why are people born?', 'Why do they die?', and
`Why do they spend so much of the intervening time wearing digital
		-- Douglas Adams, "The Hitchhikers Guide To The Galaxy"
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