On Fri, Apr 23, 2010 at 5:36 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, 23 Apr 2010, Chouteau Fabien wrote: > > > > > + * When a LUN receive an "eject" SCSI request (Start/Stop Unit), > > > > + * if the LUN is removable, the backing file is released to simulate > > > > + * ejection. > > > > + * The "eject" state of a LUN is available in the "ejected" file of the > > > > + * LUN's sysfs directory (see above). The "eject" state is only updated > > > > + * by SCSI request, not by user ejection. > > > > > > What's the reason for that? With a real removable device, like a CD > > > player, it doesn't make any difference whether the medium was ejected > > > because of a SCSI command or because I pressed the "eject" button. > > > > > > I just don't see any point in keeping track of the two actions > > > separately, since they end up having the same final result. > > > > > > > By user ejection, I mean send an empty line in the "file" sysfs entry. > > The Start/Stop request is an action from the USB host side, user > > ejection is from the USB device side, for me it's two different > > events. > > Maybe my comment is not clear about this point. > > No; it's clear enough and I understood what you meant. It's true that > they are two different events, but they have the same end result. > > > I use a FAT disk image as LUN file, users can put some files in the > > "fake" disk and then eject it. When I get the ejected signal, I mount > > the disk image on loop device and perform operations on the user's > > files. > > So I want to know when users eject the disk and only when users do. > > > > I still can use the LUN ejection from device side to disable the mass > > storage device, and in this case I don't want to mount the disk and > > search for user's files. > > Why not? Isn't it possible that the user put some files there before > the device-side eject happened? > > What happens if the user and the device both try to eject the medium at > approximately the same time? Which event occurs first will be purely > random chance. That means there's a 50% probability you will end up > doing the wrong thing. > > No, I think you need to do the same thing whenever an eject occurs, or > else find a better criterion for deciding what to do. You're right, I can do the same thing for both ejection. I'm going to resend the patch without the "eject" sysfs entry. -- Fabien Chouteau EPITA GISTR 2010 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
