The general way camera manufacturers fix this problem is by disabling the
user interface on the camera when it's connected to the USB bus.
My DC290 just runs a pretty animation on the screen while it's
communicating. The only switches that work are on/off and "mode" (which
allows me to turn off the communications mode). I can't take or erase
pictures.
That's the easy way to solve the problem. Someone else suggested
triggering media-change... if you media-change on a mounted filesystem, all
sorts of bad things happen.
In short, if you want to use the mass storage class, be a mass storage
device. If you want to be a fancier device, then don't pretend to be a
simple one.
Matt Dharm
On Wed, Apr 18, 2001 at 11:10:26AM -0600, Gordon McNutt wrote:
> Hi,
>
> My company has recently started work on a slave usb driver for a camera.
> The camera f/w can support a mass storage profile as well as a digital
> still imaging profile.
>
> I've got to wondering about the mass storage profile, and how the host
> f/s keeps in synch. I assumed the typical usage scenario was that the
> host would mount the device and get access to stored pictures. But what
> if the device snapped a new picture while it was mounted? How would the
> host filesystem learn about it without unmounting/remounting?
>
> With a "real" mass storage device like a disc drive the host f/s never
> has to worry about somebody else changing the media (I think!). All
> changes to the media pass through the host f/s.
>
> But with a camera, the camera firmware can spontaneously change the
> media.
>
> Although a sync command will update the media with host f/s changes, I'm
> not aware of anyway to do the reverse.
>
> If somebody can confirm or deny my thinking here I'd appreciate it.
>
> Thanks,
> --gmcnutt
>
>
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--
Matthew Dharm Home: [EMAIL PROTECTED]
Maintainer, Linux USB Mass Storage Driver
It was a new hope.
-- Dust Puppy
User Friendly, 12/25/1998
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